Clean Technologies doi: 10.3390/cleantechnol8040135

Authors: Catalina Calin Fatima Elamrani Daniela Popovici Sonia Mihai Andreea Bondarev Laurentiu Palade Cristina-Emanuela Enascuta Elena-Emilia Sirbu

Large volumes of solid waste are produced by the winemaking sector, which could be utilised as adsorbents to retain contaminants, providing a beneficial approach in terms of economic recovery and sustainability. The adsorption of nitrate onto biochar produced from grape pomace has not received enough attention, even though biochar-based materials have been thoroughly studied for water treatment applications. This study aims to fill the knowledge gap by assessing a low-cost mildly carbonized biochar derived from winery residues for nitrate retention and optimising the nitrate retention procedures by comprehensive physicochemical characterisation. The mildly carbonized biochar prepared from grape pomace collected from the Dealu Mare wine region (Romania) was characterized using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and thermogravimetric and derivative thermogravimetric (TGA/DTG) analyses. Results revealed a structure enriched with oxygen-containing functional groups that promote nitrate retention through combined physical adsorption and electrostatic interactions. Surface analyses after adsorption confirmed the successful immobilization of nitrate species on the biochar matrix. The adsorption performance was improved by Response Surface Methodology (RSM) method using a Central Composite Design (CCD), studying the influences of the following parameters: solution pH, adsorbent weight, nitrate concentration and time. Among all variables, pH was identified as the dominant factor controlling adsorption efficiency, reflecting the key role of surface charge interactions. The optimized conditions (175 mg/L nitrate, pH 6, 0.3 g adsorbent dosage, and 94 min contact time) resulted in a maximum nitrate removal efficiency (RE) of 86.69%, while the predictive model exhibited excellent accuracy (R2adj = 0.985). The findings demonstrate that mildly carbonized grape pomace biochar can achieve competitive nitrate removal without chemical surface modification, offering a more sustainable and economically attractive alternative to conventionally biochars. The research highlights that selecting feedstock and utilizing intrinsic surface functionality can create efficient nitrate adsorbents from agro-industrial residues.

Clean Technologies doi: 10.3390/cleantechnol8040134

Authors: Konstantinos Passadis Giannis Pachakis Dimitris Malamis

Biorefineries that convert the organic fraction of municipal solid waste (OFMSW) into advanced biofuels can integrate waste management with renewable energy production. However, their environmental performance remains insufficiently characterised owing to a scarcity of life cycle assessment (LCA) studies based on real operational data. This study presents a gate-to-gate LCA of a demonstration biorefinery processing source-separated food waste into bio-oils, bioethanol, and biogas. The ReCiPe 2016 Midpoint (H) method was applied across 18 impact categories, with system expansion crediting the displacement of rapeseed oil, maize-derived ethanol, and marginal biogas-derived electricity. The net global warming potential (GWP) was 68.5 kg CO2 eq per tonne of wet OFMSW (69% reduction from gross), placing the biorefinery 83–93% below landfilling, 63% below incineration with CHP, and above standalone anaerobic digestion systems that lack the energy-intensive drying and enzymatic hydrolysis steps of the present configuration. Bio-oil and bioethanol achieved net-negative GWP per kilogram of product (−0.89 and −0.66 kg CO2 eq, respectively), whilst eleven of eighteen categories achieved net savings under system expansion. Enzyme production dominated the bioethanol environmental profile (37–94% across categories), whilst drying dominated bio-oil (46–93%). Monte Carlo simulation confirmed that the sign of the net impact stayed unchanged across the entire 95% confidence interval (the interval did not span zero) for 17 of 18 categories.

Clean Technologies doi: 10.3390/cleantechnol8040133

Authors: Basheer Mugdadi Michael Pate James Sweeney

This study investigates the thermal, economic, and environmental performance of heat recovery ventilators (HRVs) in hot climates, which has not been thoroughly investigated because standards and applications to date have focused primarily on cold climates. Experimental testing was conducted at airflow rates of 200–350 m3/h and outdoor air temperatures of 30–45 °C, representing typical summer conditions. HRV thermal performance was evaluated by measuring airflow rates and temperatures and then determining the heat transfer rates between the two air streams. Effectiveness increased by 3.9% when the supply inlet temperature increased from 30 to 45 °C, but decreased by 9.3% when airflow increased from 200 to 350 m3/h. The overall heat transfer coefficient remained nearly constant with increasing supply temperature but increased by approximately 37% as airflow increased. The highest recovery efficiency ratio (RER), defined as the ratio of supply air pre-cooling capacity to HRV power consumption, was 26.6 Btu/W.hr at 300 m3/h and 45 °C. Economic analysis based on the reduction in ventilation cooling load yielded payback periods ranging from 2.7 to 13.3 years. Annual CO2 emission reductions ranged from 151 to 776 kg/year per HRV unit, demonstrating the environmental benefits of HRV systems in hot climates.

Clean Technologies doi: 10.3390/cleantechnol8040132

Authors: Danieli Soares de Oliveira Clainer Bravin Donadel

Access to safe drinking water remains a global challenge, particularly in decentralized and low-resource settings where conventional treatment technologies may be economically or operationally impractical. Combining low-energy hydraulic flocculation systems with biodegradable natural coagulants represents a promising strategy for sustainable water treatment. This study investigated the influence of hydraulic retention time (HRT) on the clarification performance of aluminum sulfate, Moringa oleifera, and Aloe vera in continuous-flow helically coiled tube flocculators (HCTFs). Four HRTs (1.71–6.84 min) were obtained by varying reactor length while maintaining a constant flow rate of 0.5 L/min. Synthetic water with an initial turbidity of approximately 100 NTU was treated, and clarification performance was evaluated by residual turbidity and turbidity removal efficiency. Two-way ANOVA revealed significant effects of HRT and coagulant type, as well as a significant interaction between these factors (p < 0.001), indicating that the influence of HRT depended on the dominant coagulation mechanism. Aluminum sulfate maintained consistently high turbidity removal efficiencies (96.3–98.1%) regardless of HRT. In contrast, Moringa oleifera achieved the highest clarification efficiency (99.5%) and a final turbidity of 0.49 NTU at the longest HRT, whereas Aloe vera exhibited the greatest hydraulic sensitivity, with turbidity removal increasing from 78.9% to 96.1% as HRT increased. The results demonstrate that HRT should be selected according to the dominant coagulation mechanism of the coagulant rather than adopted as a fixed design parameter. This mechanism-based approach provides a rational basis for designing and optimizing continuous-flow flocculators and supports the development of compact, efficient, and sustainable decentralized water treatment systems.

Clean Technologies doi: 10.3390/cleantechnol8040131

Authors: João Vitor Souto de Araújo Queiroz Clara Maria Marinho Serafim Emanuel Pereira do Nascimento Danilo Diniz Siqueira Renate Maria Ramos Wellen Edcleide Maria Araújo Carlos Bruno Barreto Luna

Poly(lactic acid) (PLA) is a renewable and biodegradable polymer that has attracted considerable attention for sustainable packaging applications. However, its inherent brittleness limits its use in flexible films. In this study, PLA/poly(vinyl alcohol) (PVA) blend films were prepared by a single-solvent-casting rout at PLA/PVA weight ratios of 80/20, 70/30, 60/40, and 50/50 to investigate the influence of composition on their thermal, chemical, morphological, mechanical, optical, and water vapor barrier properties. Increasing the PVA content progressively modified the molecular organization of the system, the crystallization ability of the PLA phase and promoting a more homogeneous phase distribution. These structural changes resulted in a transition from a brittle behavior to increasingly ductile films, with the PLA/PVA 50/50 composition exhibiting the most favorable combination of tensile toughness, transparency, and morphological homogeneity, reaching an elongation at break of approximately 60%. In contrast, the increase in the hydrophilic phase led to higher water vapor permeability, highlighting the trade-off between mechanical performance and moisture barrier properties. Overall, the results demonstrate that controlling the PLA/PVA ratio provides an effective strategy for tailoring the morphology and functional properties of solvent-cast PLA/PVA films, contributing to a better understanding of the composition–structure–property relationships in biopolymer blends.

Clean Technologies doi: 10.3390/cleantechnol8040130

Authors: Anastasia Memetova Nariman Memetov Tatiana Pasko Oksana Guseva Olga Zakharova

The growing volume of crustacean shell waste generated during seafood processing poses a serious environmental problem. However, this type of biowaste remains underutilized, despite being a promising renewable raw material for the production of functional carbon materials. This study aims to investigate how synthesis parameters influence the formation of a hierarchical porous structure in shrimp shell-based carbon materials and to optimize these parameters to improve CO2 adsorption efficiency. Under optimal carbonization conditions (holding time: 2 h; temperature: 650 °C) and activation conditions (holding time: 2 h; temperature: 750 °C) with activator-to-carbon weight ratios (A/C) of 1/1, 2/1 and 4/1, the resulting porous carbon samples exhibited relatively high SBET values (1175, 2708 and 3052 m2/g, respectively) and VT (0.70, 1.55 and 2.60 cm3/g, respectively), as well as different pore size distributions. Notably, the resulting carbon materials demonstrated exceptional CO2 adsorption performance at 298 K, reaching a maximum adsorption capacity of 40.03 mmol/g at 40 bar for sample SS_652_41752, 15.12 mmol/g at 15 bar for SS_652_21752, and 3.41 mmol/g at 1 bar for SS_652_11752. These values rank among the highest ever reported for biomass-derived porous carbon materials. The adsorption behavior of the most efficient sorbent, SS_652_41752, was further analyzed using Langmuir and Freundlich isotherm models over the temperature range of 298–318 K and at pressures up to 40 bar, and the isosteric heats of adsorption were calculated to elucidate adsorbent–adsorbate interactions. It was found that the differential molar isosteric heat of CO2 adsorption decreased from approximately 20 to approximately 17 kJ/mol with increasing adsorption uptake, confirming the physisorption nature of the process. These results demonstrate that crustacean shell waste is a promising feedstock for producing carbon materials with tailored properties and significant potential for CO2 adsorption applications.

Clean Technologies doi: 10.3390/cleantechnol8040129

Authors: Annarita Fiorente Germano D’Agostino Andrea Petrella Francesco Todaro Michele Notarnicola

The fastest growing waste stream worldwide is represented by Waste from Electrical and Electronic Equipment (WEEE). One of the main critical issues related to the recovery of such waste is the mixed plastic fraction, which is difficult to sort and can contain flame retardants and additives that pose a risk to human health and the environment. This study aims to validate the possibility of using tribo-electrostatic separator technologies to sort plastic polymers (e.g., PP, PA6, PS and PVC) obtained after a size-reduction operation of WEEE. The experimental study was conducted on a 10 kg/h laboratory-scale pilot plant. Several parameters were analysed during the tribo-charging and electrostatic separation processes, including the rotation speed and residence time of the particles in the tribo-charging device as well as electrode voltage, and the distance between the deflectors and the electrodes in the electrostatic separator. The results show that the tribo-electrostatic separation technologies are promising and efficient for plastic waste recycling. In fact, under specific conditions, it is possible to achieve high recovery rates (>70%) and purity levels (>76%) that allow the reintegration of plastic polymers into the economic cycle as a secondary raw material.

Clean Technologies doi: 10.3390/cleantechnol8040128

Authors: Emanuele Di Bisceglie Armando Vitale Francesca Rita Famà Alessandro Antonio Papa Umberto Pasqual Laverdura Maria Luisa Grilli Andrea Di Carlo Giuseppina Vanga

This work presents a techno-economic assessment of hydrogen production via sorption-enhanced gasification (SEG) of hazelnut shells across three plant scales (100 kWth, 1 MWth, and 10 MWth). The overall model is developed through the integration of Aspen Plus® process simulation, coupled with MATLAB®-based kinetic reactor modelling, enabling the assessment of the entire process chain. The kinetic SEG model, validated against experimental literature data, was implemented to describe the fluidized bed gasifier behaviour at the three scales. The resulting process streams were subsequently integrated into Aspen Plus® for downstream upgrading and overall system analysis. The simulations show that the SEG process produces a hydrogen-rich syngas with H2 contents around 80 vol.%dry-basis, which is further upgraded to a hydrogen purity of 99.95% with a recovery of 90% via pressure swing adsorption. The process exhibits stable performance across scales, with Cold Gas Efficiency values around 60% and hydrogen yields close to 1 Nm3/kgBiomass. The economic analysis highlights a decrease in the Levelized Cost of Hydrogen (LCOH) from 41.3 €/kg at 100 kWth to 6.8 €/kg at 10 MWth. These results indicate that SEG represents a promising pathway for low-carbon hydrogen production, while enabling the valorisation of biogenic residues within a sustainable energy framework.

Clean Technologies doi: 10.3390/cleantechnol8040127

Authors: Shailendra Pawanr Kapil Gupta

Understanding the carbon emission characteristics of fused filament fabrication (FFF) is important for the development of more sustainable additive manufacturing practices. This study presents a framework for quantifying, modelling, and optimizing the carbon emissions of FFF-printed specimens of carbon-reinforced Polyethylene Terephthalate Glycol (PETG-CF) composite. Carbon emissions were assessed within a cradle-to-gate system boundary by considering material consumption and electrical energy usage during fabrication. The influence of print speed, raster angle, layer height, infill density and infill pattern on carbon emissions were experimentally investigated. Response Surface Methodology (RSM) was utilized to formulate a predictive carbon emission model, while analysis of variance was applied to assess the significance of the process parameters. The findings revealed that infill density, infill pattern, layer height, and raster angle significantly affected carbon emissions, while print speed showed a comparatively lower influence. Contour plot analysis was used to visualize parameter interactions and identify low-emission regions. RSM-based optimization predicted a minimum carbon emission of 0.0732 kgCO2eq at a print speed of 220 mm/s, layer height of 0.12 mm, infill density of 50%, raster angle of 0°, and rectilinear infill pattern. The proposed framework presents a practical strategy for integrating carbon emissions for a sustainable FFF process.

Clean Technologies doi: 10.3390/cleantechnol8040126

Authors: Megan Rand Wheeler Brandi Everett Steven M. Williamson Victor Prybutok

The rapid global expansion of data center infrastructure has prompted substantial clean technology research on energy, water, and carbon impacts, while the acoustic health dimension of these facilities remains virtually unstudied. Existing occupational and environmental noise assessments rely on A-weighted (dBA) metrics, which apply more than 26 decibels (dB) of attenuation at 63 hertz (Hz) and exceed 50 dB at infrasound frequencies, sharply discounting their sensitivity to infrasound and low-frequency noise (ILFN) generated by data center cooling fans, heating, ventilation, and air conditioning (HVAC) systems, backup generators, and power transformers. This narrative review synthesizes evidence from established ILFN health research alongside the emerging data center acoustics literature, identifying a consequential gap: no published study has measured the ILFN spectrum of an operational data center, nor examined health outcomes in workers or surrounding communities with respect to sub-audible acoustic exposure. Evidence from wind turbine, industrial, and laboratory contexts documents non-auditory ILFN pathways, including sleep disturbance, cardiovascular stress responses, cognitive impairment, and audiovestibular symptoms—effects that operate below the auditory threshold and are substantially undercounted by standard dBA monitoring. A prioritized research agenda is proposed, beginning with G-weighted and flat-response ILFN characterization of operational data centers across at least 1–200 Hz—a prerequisite for evidence-based acoustic design standards and health-protective infrastructure development consistent with clean technology principles.

Clean Technologies doi: 10.3390/cleantechnol8040125

Authors: Guillermo Valencia Víctor Merlano Cesar Isaza

This study evaluates, from energy, exergy, exergo-sustainability, and environmental perspectives, two combined-cycle configurations based on a supercritical CO2 Brayton cycle coupled to an ORC: a simple reheat configuration (S-CO2-ORC) and a recompression-reheat configuration (SRC-CO2-ORC). Both were assessed under two thermal sources: concentrated solar power (CSP) and a hybrid biomass-CSP source using oil palm residues. Sizing was based on the cooling demand of a 130-home residential complex in Barranquilla, estimated at 152 kW through hourly simulation. The SRC-CO2-ORC configuration delivered the best energy performance, reaching 138.38 kW and 55.34% with CSP and up to 157.28 kW and 57.66% under hybrid operation. The highest irreversibilities were concentrated in the solar field and receiver, while the thermal sources contributed more than 85% of the total carbon footprint. The lowest life-cycle impact corresponded to the SRC-CO2-ORC-Solar configuration, at 0.0117 kg CO2-eq/kWh, against 0.0194 kg CO2-eq/kWh for the S-CO2-ORC-Hybrid case. The results confirm the technical feasibility of these configurations for residential applications and reveal a clear trade-off between thermodynamic performance and minimum carbon footprint.

Clean Technologies doi: 10.3390/cleantechnol8040124

Authors: Yasemin Ebru Atmaca Päivi Kivikytö-Reponen Jari Halme

This study quantified environmental impacts of circularity strategies in the manufacturing industry, focusing on maintenance-driven product lifetime extension (PLE) using Life Cycle Assessment (LCA). The analyzed case builds on earlier work, which showed that the product’s lifetime was shorter than the industry average lifetime and that the use phase was the dominant contributor to overall environmental impacts, identifying it as a key area for improvement. A computational code was developed to model maintenance-driven lifetime extension scenarios and to calculate selected total and normalized environmental impacts for the studied industrial process equipment. The model assumes maintenance-related impacts are smaller than the impacts avoided through reduced new production. Results show that while total impacts increase with longer use, normalized impacts per unit of production and per year of service life decrease by 58%, improving resource efficiency. Maintenance-driven PLE supports circular economy (CE) strategies by slowing material flows and extending product use. The findings highlight the importance of incorporating maintenance into circularity frameworks and life cycle-based decision-making.

Clean Technologies doi: 10.3390/cleantechnol8040123

Authors: Leandro Camargo Renato Silva Yuri Meyer Wislei Osório

This study proposes a hydrogen-powered industrial ride-on scrubber (IRoS) investigated by using in situ and on-board H2 production. Technological and financial calculations involving conventional liquefied petroleum gas (LPG), an electric battery, and a hydrogen-powered system in IRoS are discussed. Energy consumption, operational costs, financial aspects and environmental impacts are also discussed. Investment payback analyses to replace an LPG machine are discussed. For 10 years, the highest operational costs and downtime costs are of the LPG-powered scrubber (USD ~187k). The two other systems are substantially lower, i.e., ~4% and 7%. CO2 emissions of the three examined scrubbers ranged between 162 and 194, 10 and 13, and 5 and 9 tCO2, respectively. Gravimetric energy density (GED) reveals that the LPG-powered system is ~2× and 10× higher than the battery- and H2-powered systems, respectively. Adequate modulation and control of the produced H2 volume in Al hydrolysis are keys to success in the H2-powered scrubber project. For this purpose, three aspects are important: i. adequate selection of Al-based alloy or mixture powders, ii. the nature and concentration of alkali solution and iii. the quantity of solid (Al-based alloy or mixture powders) per volume of alkali (liquid), designated as S/L ratio.

Clean Technologies doi: 10.3390/cleantechnol8040122

Authors: Jhoan Sebastián Valderrama-Vélez Karen Lemmel-Vélez Juan Camilo Mazo-Arenas Carlos David Zuluaga-Ríos

Reliable experimental platforms are essential for lithium-ion (Li-Ion) battery characterization, equivalent circuit model (ECM) identification, and state-of-charge (SOC) estimator validation. However, access to commercial battery cyclers and high-end instrumentation can be limited in academic and applied research environments, which motivates the development of low-cost and reproducible test benches. This work presents the development and validation of a low-cost experimental platform for Li-Ion battery characterization, SOC-dependent ECM identification, voltage model validation, and SOC estimator assessment. The proposed platform integrates constant-current–constant-voltage (CC-CV) charging, a controlled-current electronic load implemented on a printed circuit board (PCB), ESP32-based embedded acquisition, and MATLAB-based data processing. A Samsung INR18650-35E cell was characterized through full-discharge tests at different C-rates, pulse discharge tests (PDTs), and dynamic current profiles. The measured capacity at 0.2C was 3345.1 mAh, showing close agreement with the manufacturer-reported minimum nominal capacity of 3350 mAh. First- and second-order Thévenin ECMs were identified from PDT data, parameterized as SOC-dependent models, and validated under Scaled Dynamic Stress Test (DST) and Modified Pulsed Dynamic Stress Test (P-DST) profiles. The second-order ECM identified from the most complete PDT dataset achieved voltage RMSE values of 23.24 mV and 12.14 mV under the DST and P-DST profiles, respectively. The platform was further used to evaluate SOC estimators based on extended Kalman filters (EKF) and a hybrid Extended Kalman Filter-Artificial Neural Network (EKF-ANN) residual correction method. The EKF based on the second-order ECM achieved SOC RMSE values of 0.5088% and 1.0890% under the complete dynamic profiles, while the hybrid EKF-ANN reduced the RMSE to 0.2276% and 0.2788% over the dynamic test blocks. These results show that the proposed platform provides an accessible experimental framework for connecting battery testing, ECM identification, voltage validation, and BMS-oriented SOC estimator evaluation within a single reproducible workflow.

Clean Technologies doi: 10.3390/cleantechnol8040121

Authors: Xiaoyan Zheng Lixia Wang Yingdui He Binling Ai

Aerobic composting is an important pathway for the resource utilization of agricultural waste. However, nitrogen loss during composting not only reduces the nutrient value of the final product but also causes environmental burdens, particularly through ammonia (NH3) volatilization and nitrous oxide (N2O) emissions. The objective of this review is to systematically summarize the sources, pathways, and mechanisms of nitrogen loss during aerobic composting of agricultural waste and to evaluate multi-scale control strategies for enhancing nitrogen retention and mitigating environmental emissions. This review addresses an important gap by integrating the sources, pathways, and mechanisms of nitrogen loss with practical mitigation strategies across the feedstock, in-process, post-treatment, system design, and macro scales. The synthesis indicates that the major nitrogen loss routes during aerobic composting include NH3 volatilization, N2O emissions, and nitrate leaching. From a multiscale perspective, the review synthesizes control strategies spanning feedstock pretreatment, including optimization of carbon-to-nitrogen (C/N) ratio, adsorbent amendment, and microbial inoculation; in-process regulation, including aeration, moisture, temperature, pH; and post-treatment approaches for nitrogen stabilization and resource recovery. The supporting roles of reactor innovation, intelligent process control, and policy and regulatory measures are also discussed. Finally, current bottlenecks and future research directions are summarized from environmental and economic perspectives, with particular emphasis on interdisciplinary integration and technological innovation to enhance nitrogen retention during composting.

Clean Technologies doi: 10.3390/cleantechnol8040120

Authors: Ammar Bany-Ata Hamzah Bany-Ata Hussein Kokash Sameeh Baqain Mwafak Shakoor

Power-to-Ammonia-to-Power (P2A2P) systems in hot-arid MENA climates reject waste heat through Recuperated Organic Rankine Cycles (RORCs) whose condensation temperature tracks ambient conditions across annual swings exceeding 35 K. Standard exergoenvironmental assessments evaluate priorities at a single dead-state temperature, an assumption this study terms the Static T0 Fallacy. A four-way advanced exergy decomposition is combined with an off-design model (Stodola’s ellipse, constant-UA scaling) to sweep the dead-state temperature from 5 ∘C to 40 ∘C. At T0=20 ∘C, 95.8% of total exergy destruction is endogenous, confirming weak inter-component coupling. The condenser carries the largest avoidable environmental impact rate (4.02 mPts/h, 74% of the system total). At T0=37.4 ∘C, the recuperator undergoes a priority inversion from destruction-dominated (fb=14.7%) to fully capital-dominated (fb=100%). Ammonia’s wet-fluid thermodynamic coupling eliminates the recuperator’s duty as the condensation temperature approaches the cold-side outlet constraint. The recuperator’s avoidable environmental impact rate drops by 100% relative to the standard assessment, while the condenser’s rises by 49%. This inversion mechanism is fluid-specific: the ammonia recuperator’s endogenous fraction reaches 99.5% at T0=20 ∘C. The toluene recuperator, swept at its own independently optimised operating point, has an endogenous fraction between 59.08% and 82.31% over the same range. For P2A2P installations where the annual ambient swing exceeds 15 K, exergoenvironmental analysis should be performed at both design-season and summer-peak dead-state temperatures, with the summer-peak result governing capital allocation.

Clean Technologies doi: 10.3390/cleantechnol8040119

Authors: Ivan Zubkov Yuri Korolev Ekaterina Korsunova Alina Petrenko Evgeniy Sadyrin Alexey Saliev Victor Klushin

Managing polymer waste, primarily polyolefins—low- and high-density polyethylene and polypropylene—is a critical challenge in the transition to a low-carbon, circular economy. Traditional approaches (landfilling and incineration) are inconsistent with sustainable development principles and increasingly stringent extended producer responsibility regulations, while chemical recycling, particularly catalytic pyrolysis, is considered a key technology for returning hydrocarbon feedstocks to the production cycle. This mini-review systematizes and analyzes current advances in the catalytic pyrolysis of polyethylene and polypropylene. An algorithm for selecting a recycling route for polyolefin-containing waste based on its composition, degree of degradation, and the presence of hazardous additives is proposed. Existing and planned industrial projects in the field of chemical recycling of polyolefins are assessed, and challenges and prospects for technology commercialization are outlined. It is demonstrated that catalytic pyrolysis has the potential to become a key element of a circular economy for plastics, ensuring decarbonization and resource conservation with further optimization of catalysts and process flowsheets.

Clean Technologies doi: 10.3390/cleantechnol8040118

Authors: Zafer Utlu Büşra Selenay Önal

Hydrogen-based technologies are widely considered promising pathways for decarbonizing power generation and industrial energy systems; however, their overall sustainability depends strongly on both production routes and conversion efficiencies. This study presents a comparative energy and exergy analysis of hydrogen-based decarbonization pathways under a consistent 1 MW net electrical output boundary, including natural gas combustion (S0), grey hydrogen combustion (S1), grey hydrogen fuel cell (S2), green hydrogen combustion (S3), and green hydrogen fuel cell (S4) systems. The results indicate that combustion-based pathways (S0, S1, and S3) exhibit relatively low energy efficiencies of approximately 30–40% and exergy efficiencies of 25–40%, accompanied by high exergy destruction levels generally exceeding 60%. In contrast, fuel cell-based configurations (S2 and S4) demonstrate improved conversion-stage thermodynamic performance, achieving energy efficiencies of 50–60% and exergy efficiencies of 45–65%, while reducing exergy destruction due to electrochemical conversion and lower irreversibilities. A detailed comparison shows that the natural gas reference system reaches an exergy efficiency of 33.7%, whereas the hydrogen fuel cell system achieves 46.5%, corresponding to approximately 42% lower exergy destruction and about 36% reduced fuel input. From an environmental perspective, the simplified carbon assessment indicates that natural gas combustion generates approximately 577 kg CO2/h. Grey hydrogen pathways remain associated with substantial upstream emissions, generating approximately 857 kg CO2/h for grey hydrogen combustion and 545 kg CO2/h for grey hydrogen fuel cell operation under the 1 MW net electrical output basis. In contrast, green hydrogen-based pathways are assumed to have near-zero direct/upstream operational CO2 emissions under renewable-powered production assumptions. Overall, the findings show that hydrogen use alone does not guarantee decarbonization; rather, both the hydrogen production route and the final conversion technology must be considered to achieve thermodynamically efficient and low-carbon power generation.

Clean Technologies doi: 10.3390/cleantechnol8040117

Authors: Antonina Andreevna Filimonova Hristo Ivanov Beloev Ruzina Farsilovna Kamalieva Alena Yurevna Vlasova Iliya Krastev Iliev Ivan Hristov Beloev

The article presents the results of the development of multicomponent adsorption materials based on industrial waste sludge from the water treatment plant of a thermal power plant. Activation of the sludge at 1000 °C makes it possible to obtain a porous matrix. It has been experimentally established that compositions with 50% activated sludge content in combination with oxides of Zn, Fe, Mn, Cu and NaOH have an optimal sorption capacity with respect to hydrogen sulfide. Kinetic studies have shown that the optimal contact time of the adsorbent with the adsorbate is 15–20 min, and the operating temperature should not exceed 300 K. The calculated thermodynamic parameters confirm the exothermic chemical mechanism of sorption. The materials have the ability to regenerate and display a color change upon contact with hydrogen sulfide. With respect to mercaptan sulfur, the maximum capacity was achieved for the sorption composition with 74.7% ZnO content. The logarithmic dependence of the mercaptan sulfur capacity on the percentage of zinc oxide in the composition has also been established. The environmental significance of the work lies in the utilization of large-tonnage waste and the absence of liquid effluents during regeneration. The proposed materials show promise as potentially cost-effective alternatives for gas purification, though comprehensive economic analysis remains the subject of future work.

Clean Technologies doi: 10.3390/cleantechnol8040116

Authors: Stefania Fiameni Francesca Visentin Adriana Bernardi Nicola Mutinelli Simone Battiston Alessandro Bortolin Luc Pockelè Monica Favaro Maria Losurdo

Global decarbonization represents one of the defining challenges of the 21st century. Geothermal energy offers a robust alternative for reducing fossil fuel dependency for both residential and industrial heating and cooling. While shallow geothermal systems are versatile and high-performing, comprehensive Life Cycle Assessments (LCA) remain scarce in the literature. This study evaluates the environmental impact of the manufacturing and installation processes of next-generation coaxial probes featuring a galvanized steel outer tube and an internal polyethylene pipe. The LCA identifies material composition as the primary environmental driver: steel production accounts for 41% of the total impact, while the hot-dip galvanization process contributes 30%, significantly affecting the “climate change” and the “resource use” categories. A comparative LCA with conventional double U-tube installations shows similar overall environmental impacts. A sensitivity analysis on the coaxial probes was conducted to explore potential mitigation strategies aimed at reducing the associated environmental impacts, providing indications for sustainable eco-design. The LCA results demonstrate that optimizing the design, specifically by reducing the steel quantity in the coaxial outer tube and avoiding the zinc coating process, results in a 34% reduction in total environmental impact, confirming that LCA is a fundamental tool for supporting the environmental sustainability of developing technologies.

Clean Technologies doi: 10.3390/cleantechnol8040115

Authors: Marco dos Santos Bernardes

Transport decarbonization requires infrastructure that can use time-resolved carbon information without overstating the representativeness of short proof-of-method runs. This study introduces Adaptive Energy Stations (AESs), multi-fuel transport-energy nodes that integrate marginal grid-emission signals, fuel life-cycle carbon intensities, wholesale electricity prices, and vehicle operating constraints into a station-level dispatch optimization. The implemented case is a one-week winter proof-of-method for CAISO/CAISO_NORTH using 168 hourly service events over 1–8 January 2026 Pacific time, archived WattTime marginal operating emissions, CAISO locational marginal prices, eGRID CAMX annual-average factors, and declared vehicle and fuel-pathway parameters. In the audited CAISO scenario, the attached dispatch outputs report a reduction from 181.76 to 123.38 g CO2e/km relative to the specified static baseline, corresponding to a 32.12% reduction for the one-week winter service-event stream. The populated dispatch trace shows that the carbon-priority AES plug-in hybrid electric vehicle (PHEV) run selected cellulosic E85 for all 168 events and selected no electric events; this result is interpreted as an operational scenario result for the archived week, not as an annual fleet-average, smart-charging benefit, or deployment forecast. The revised analysis explicitly separates implemented CAISO evidence from ERCOT, MISO-MROW, and ISO–NE extension sensitivities, which remain hypothetical until equivalent marginal-emissions, price, and service-event data are supplied. Battery-production amortization is treated as a separate sensitivity because it can change battery electric vehicle (BEV)–cellulosic E85 equivalence conclusions: at 50–100 kg CO2e/kWh over 240,000 km, a 75 kWh BEV pack contributes 15.6–31.3 g CO2e/km and a 14 kWh PHEV pack contributes 2.9–5.8 g CO2e/km. Practical-equivalence claims are therefore conditional on the declared boundary, equivalence margin, and production-emissions treatment. Full deployment requires validated marginal-emission access, transparent dispatch-audit outputs, supply-chain verification, user-behavior characterization, cost sensitivity analysis, and cybersecurity safeguards.

Clean Technologies doi: 10.3390/cleantechnol8040114

Authors: Sofia Faershtein Wayde Martens Graeme Millar

Red mud is a waste byproduct of alumina production. Its release into the environment poses risks, highlighting the need for strategies to limit pollution. Using red mud as a filler in polymer-matrix composites can reduce the leaching of heavy metals and metalloids. We fabricated composites with high red mud content (up to 60 wt.%) using two particle fractions (<125 μm and <500 μm). The study examined how filler concentration and particle size affected the composites’ microstructure and mechanical properties. Results showed that composites with smaller particles had better encapsulation and enhanced structural qualities, such as reduced porosity and fewer cracks. Among four filler mass loadings (20, 30, 40, and 60 wt.%), composites with 40 and 60 wt.% red mud exhibited greater epoxy penetration into agglomerates and partial deagglomeration, resulting in small, uniformly dispersed red mud particles within the matrix. Calorimetry analysis demonstrated that increasing the red mud concentration slows the curing process: for composites with 20 wt.% red mud, the curing time is approximately 10 h, whereas for composites with 60 wt.%, approximately 35 h. We performed a thorough environmental safety evaluation of high-loaded red mud–epoxy composites in accordance with the standard AS 4439.3:2019. The tests showed that epoxy resin significantly reduces the levels of potentially hazardous elements, such as Na and Al, in the leachates, demonstrating the safety of the composites. Composites with 40 wt.% red mud (particle size < 125 μm) showed the most effective epoxy impregnation into red mud agglomerates and demonstrated the best encapsulation behaviour, releasing the least amount of metals compared to red mud during both 20 h and 4-week, long-term leaching tests.

Clean Technologies doi: 10.3390/cleantechnol8040113

Authors: Helena M. Ramos Chetan Rishi Oscar E. Coronado-Hernández Modesto Pérez-Sánchez Paul Coughlan Aonghus McNabola

Hybrid renewable energy systems (HRESs) represent a promising strategy for reducing carbon emissions across multiple sectors by integrating complementary resources such as solar, wind, hydropower, and energy storage technologies. Identifying the most suitable location for a pilot installation requires a comprehensive evaluation that balances technical performance, environmental benefits, social considerations, and economic feasibility. This study employs an enhanced multi-criteria decision analysis (MCDA) framework, supported by machine learning (ML) techniques, to assess four pilot sites developed within the HY4RES project: a rural community, an aquaculture facility, a port installation, and an agriculture network. A comprehensive set of key performance indicators (KPIs) was established to capture technical, environmental, social, and economic dimensions. These include the degree of hybridization, carbon intensity, community benefit scores, net present value, levelized cost of energy, and payback period. After collecting and normalizing the site-specific data, ML EL-SVM, decision tree, and logistic regression models as computational surrogates designed to bypass the multi-step, matrix inversion mathematical requirements of the AHP when screening massive numbers of future scenario outputs supporting consistency checks and sensitivity exploration were used, along with criterion adjustments, to refine the relative importance of each KPI. The Analytical Hierarchy Process (AHP) was employed to assess potential factors and rank the sites, with the rural site achieving the highest overall score in the system, driven by its complex four-source hybrid configuration and strong community-level benefits. The agriculture scheme ranked second, demonstrating significant potential for carbon emission reductions. The port pilot placed third, distinguished by high technical innovation but more limited social impact. The aquaculture site ranked fourth, primarily due to environmental scores, despite its economic self-sufficiency.

Clean Technologies doi: 10.3390/cleantechnol8040112

Authors: Kaustav Nath Biswajit Debnath Ranjana Chowdhury Somil Thakur Rajnish Calay

Algal cultivation has attracted significant attention due to CO2 biocapture and potential for biofuel generation. Enormous generation of waste polymer often poses an environmental problem due to non-biodegradability. This study comprehensively analyses the thermal degradation characteristics of blue–green alga, Leptolyngbya subtilis JUCHE1 (LS) and waste textile polyester (WTP) and their mixtures (LS1P3 (1:3); LS1P1 (1:1); LS3P1 (3:1)) during co-pyrolysis. The interaction between LS and WTP during co-pyrolysis has been assessed through the verification of synergism using different blending ratio and through the comparison of the corresponding values of the Comprehensive Pyrolysis Index (CPI). The composite, LS1P3, exhibited the highest synergism and the maximum value of CPI. Isoconversional models (FWO, Starink, Bosewell and Tang) have been used to predict the activation energies (Ea). Thermodynamic parameters, namely, heat of reaction (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS), have also been determined for all. The average value of Ea for LS1P3 is also the lowest (96.015 kJ/mol) among all composites. The Master plot method identifies that there is a shift of reaction mechanism from phase boundary type (R2 and R3) for LS and WTP to a P2-type acceleratory reaction rate mechanism for LS1P3. The lowest average value of ΔH and the highest values of ΔG and ΔS for LS1P3 co-pyrolysis also support the least consumption of energy and the highest favorability under present conditions. The product yield distribution of co-pyrolysis in the isothermally operated conditions (450 °C) also establishes the superiority of LS1P3. Yields of pyro-oil and pyro-gas are the highest among all composites. The study ensures the future application prospects of co-pyrolysis of LS and WTP as a means for generation of energy resources (pyro-oil and pyro-gas) and chemicals (pyro-char).

Clean Technologies doi: 10.3390/cleantechnol8040111

Authors: Aigerim Akylbayeva Yerzhan Nussupov Zhansaya Omarova Ayazhan Dossymbekova Yevgeniy Korshikov Makhabbat Abdizhalel Bergaliyeva Saltanat Abdurakhman Aldiyarov Darkhan Yerezhep

Perovskite solar cells (PSCs) have emerged as a disruptive photovoltaic technology for aerospace and extreme environment applications, driven by their substantial power-to-weight ratio and mechanical flexibility. However, continuous operation under harsh conditions, characterized by the AM0 spectrum, deep vacuum, extreme thermal cycling, and ionizing radiation, exposes the fundamental thermodynamic instability of traditional organic–inorganic hybrid perovskites. This comprehensive review systematically synthesizes 131 recent studies to provide a holistic framework for designing ultrastable, radiation-hardened PSCs. We critically examine the underlying degradation mechanisms, including vacuum-induced volatile desorption, UV-triggered halide segregation, and thermomechanical fracture at buried interfaces. To overcome these critical barriers, we highlight advanced engineering strategies: the transition to all-inorganic CsPbX3 and lead-free double/chalcogenide perovskites (e.g., Cs2SnI6, CaHfS3), the implementation of dopant-free inorganic transport layers coupled with self-assembled monolayers (SAMs) for cascade band alignment, and the integration of polymeric scaffolds for fracture energy toughening. Furthermore, we emphasize the imperative shift toward solvent-free vacuum deposition techniques (ALD, PLD). A distinctive focus of this review is the integration of Artificial Intelligence; specifically, we evaluate Deep Learning architectures, such as Long Short-Term Memory (LSTM) networks, for predictive State of Health (SOH) monitoring, underscoring the vital transition from simulated to empirical datasets. Finally, coupled with Material Flow Cost Accounting (MFCA), this review outlines a strategic roadmap for the commercialization and deployment of autonomous, self-diagnosing photovoltaic platforms in next-generation satellite and deep-space missions.

Clean Technologies doi: 10.3390/cleantechnol8040110

Authors: Oluwafemi Ige Musasa Kabeya

Cement production remains one of the largest industrial sources of anthropogenic carbon dioxide (CO2) because of process emissions from limestone calcination and high-temperature fuel combustion. The primary objective of this study is to quantify the comparative effects of isolated and integrated mitigation portfolios on annual and cumulative global cement emissions through 2050 and to identify the principal leverage points needed for deep sectoral decarbonization. To achieve this, a global aggregate system dynamics model was developed and anchored to a 1990–2022 historical production baseline. The model evaluates five internally consistent scenarios: business-as-usual (BAU), efficiency and alternative fuels (EFF), materials efficiency and clinker substitution (MAT), carbon capture and storage (CCS), and an integrated net-zero-emission (NZE) pathway. The results show that while efficiency improvement alone (EFF) reduces 2050 annual emissions by 14.0% relative to BAU, it does not reverse sector-wide emissions growth. Deep decarbonization requires both substantial clinker-demand reduction (MAT, 33.2%) and broad CCS deployment (CCS, 61.1%). Only the integrated NZE pathway achieves an 87.9% reduction, lowering 2050 direct emissions to 325.8 Mt CO2. Cumulative emissions analysis further shows that delayed structural mitigation results in a large long-term carbon burden, with BAU accumulating 72.86 Gt CO2 over 2023–2050 compared with 40.07 Gt CO2 in the NZE case. A 5000-run Monte Carlo uncertainty analysis confirms that the scenario ranking remains robust under bounded-parameter variation and identifies CCS penetration and the clinker-to-cement ratio as the most influential determinants of long-term mitigation performance. Overall, the study provides a reproducible and policy-relevant framework showing that cement decarbonization cannot rely on single-technology measures, but instead requires coordinated early action across materials efficiency, alternative fuels, and large-scale carbon capture.

Clean Technologies doi: 10.3390/cleantechnol8040109

Authors: Toshifumi Fujita Akiomi Ushida

The development of detergent-free washing technologies has become increasingly important due to growing environmental concerns associated with synthetic surfactants. This study investigated the washing performance obtained by combining alkaline electrolyzed water (AlEW) with ultra-fine bubble (UFB) water within a two-stage washing process consisting of immersion pre-washing and alternating-flow main washing. During immersion washing, AlEW exhibited a pronounced cleaning effect, attributable to alkaline hydrolysis and saponification reactions as well as enhanced electrostatic repulsion between soils and fibers. In contrast, acidic electrolyzed water caused coagulation of proteinaceous soils and did not facilitate subsequent cleaning. When AlEW pre-washing was followed by alternating-flow washing using UFB water, a significant improvement in washing rate was obtained compared with deionized water. This enhancement was interpreted as the result of combined effects among chemical soil weakening, strong mechanical forces generated by alternating flow, and UFB-related physicochemical processes. Increasing the immersion time in AlEW further improved washing performance, demonstrating the time-dependent progression of the chemical pre-treatment. Overall, the optimal washing sequence consisted of AlEW immersion followed by UFB-assisted alternating-flow washing, which yielded the highest washing efficiency among all tested conditions. These findings highlight the potential of integrating electrolyzed water and ultra-fine bubble technologies to develop high-performance, low-environmental-load, and detergent-free washing systems suitable for developing environmentally benign washing approaches.

Clean Technologies doi: 10.3390/cleantechnol8040108

Authors: Tania Irene Lagunes Vega Sergio A. Zamora Castro Rogelio de Jesús Portillo Vélez Óscar Velázquez Camilo Joaquin Sangabriel Lomeli Lorena del Carmen Santos Cortés Luis Carlos Sandoval Herazo

The construction sector is responsible for approximately 38% of global CO2 emissions, driven primarily by energy demand for thermal comfort. This research evaluated the implementation of a Passive Climate Control System (PCCS) based on circular economy principles. This system acts as a thermal buffer composed of recycled PET bottles filled with 500 mL of water and a reflective coating, installed on the roof slab. Through a case–control study in Veracruz, Mexico, hygrothermal performance was monitored for ten months. The results demonstrated the superiority of the PCCS over the conventional slab: in autumn–winter, temperature fluctuations were reduced by 26.7%, while in spring–summer, the maximum temperature was limited by 1.3 °C during the daytime peak. Fractal analysis confirmed that the PCCS promotes a homogeneous thermal distribution (Fd ≤ 1.255), maintaining internal conditions within the comfort zone. The implementation of this PCCS, based on waste valorization, is a robust and sustainable solution that offers a viable alternative to active climate control. It promotes hygrothermal comfort and reduces energy consumption, aligning with the objectives of Clean Technology and building efficiency.

Clean Technologies doi: 10.3390/cleantechnol8040107

Authors: Xingqiang Song Chuan Wang Patrik Wikström Niina Leskinen Monica Joon

The stainless steelmaking process generates substantial volumes of metal hydroxide sludge during neutralization after pickling. The sludge contains valuable materials, including fluorspar (CaF2) and alloy-containing compounds. So far, life cycle assessment (LCA) of resource recovery and reuse pathways for pickling sludge remains absent in the literature. This study conducted a comprehensive LCA of a real-world Swedish case study in which the sludge is thermally processed into a usable product (Hydrofluss) and utilized in the argon oxygen decarburization (AOD) process in stainless steelmaking. Using the Product Environmental Footprint (PEF) 3.1 method and ecoinvent v3.11 in SimaPro v10.3.01, the results showed that using 1 ton of Hydrofluss can reduce the total life-cycle climate change impact by 91.6 kg CO2eq, corresponding to a 6% reduction compared with a reference scenario relying on natural fluorspar and primary ferroalloys. The sensitivity analysis indicated that replacing fossil heating oils with renewable HVO100 in the Hydrofluss recovery process could substantially enhance the climate benefit of the studied system, resulting in a six-fold (540.3 kg) CO2eq emission reduction. Beyond climate change, this study highlights the need for multi-impact LCAs to provide a more holistic understanding of the environmental implications of resource recovery and utilization systems. In a broader context, the findings can contribute to the development of more sustainable and circular resource flows and associated business models for stainless steelmaking.

Clean Technologies doi: 10.3390/cleantechnol8040106

Authors: Miriam Benitez Jo Smith Jose Ros-Lis

The current trend towards decarbonization has increased the pressure towards land use change through the installation of solar parks on agricultural fields. The usefulness of RothC to model the evolution of soil carbon after the installation of the solar park has been validated in a field with historic data. The model has been applied to evaluate the impact of a large-scale modification of land use in Valencia (Spain), a mediterranean region with an ambitious plan for the installation of renewable energy. The removal of the orange trees for the installation of a solar park would generate a carbon release in CO2 eq to 72 Mg ha−1. If the soil is left vacant of vegetation, another 28 Mg ha−1 would be emitted in 30 years. By contrast, if the soil is covered by scrubland, an overall CO2 capture of −226 Mg ha−1 could be achieved, including the impact of the initial plant removal. If we consider the Valencia region, the installation of 12.000 hectares of solar parks could generate up to 1.2 × 106 Mg of CO2 emissions or capture 2.7 × 106 Mg of CO2. Also, a sensitivity analysis to evaluate the effect of the main labels has been performed, revealing that the original carbon content is the most relevant label, followed by plant input and the % of soil covered by the solar panels. The limited availability in experimental data means that this study should be considered an exploratory evaluation of the impact of including plantations in solar parks.

Clean Technologies doi: 10.3390/cleantechnol8040105

Authors: Tania Rus Octavian Pop Lucian Fechete-Tutunaru

This study presents a cradle-to-grave Life-Cycle Assessment of a multifunctional building-integrated photovoltaic (BIPV) skylight system combining a recycled aluminum frame, double-glazing unit, semi-transparent cadmium telluride (CdTe) photovoltaic glass, and an organic phase change material (PCM) for passive thermal regulation. Assessed over a 30-year service life in accordance with EN 15804+A2 using One Click LCA, the system is evaluated across 13 environmental impact categories for a declared unit of 0.72 m2. Results show that materials production is the dominant environmental driver across all categories, contributing 72.0% of total GWP (78.00 kg CO2-eq). Component replacement is the second contributor with 9.8% of GWP. End-of-life burdens account for 7.7% of cradle-to-grave GWP. When Module D credits are included, the system achieves an indicative net GWP balance of −808.34 kg CO2-eq, that is conditional on a static Romanian grid-mix assumption; under progressive grid decarbonization this benefit is reduced, so the figure should be read as scenario-dependent potential rather than an immutable property of the product. Abiotic depletion of mineral elements is the only category where Module D does not fully offset system burdens, highlighting the relevance of critical raw material considerations for CdTe technologies. These findings demonstrate that BIPV depend on low-impact manufacturing and underscore the importance of multi-indicator LCA as the appropriate evaluation framework for integrated energy-generating building products.

Clean Technologies doi: 10.3390/cleantechnol8040104

Authors: Daniela Casamayor-Roberto Alejandro Ariza-Pérez David Ortega-Domínguez Vicente Montes Rafael Estevez Francisco J. Urbano Alberto Marinas Francisco J. López-Tenllado

The global proliferation of plastic waste has made the search for sustainable chemical recycling strategies imperative to transition toward a circular bioeconomy. This study presents a dual-valorization approach for polylactic acid (PLA) waste, utilizing it both as a sustainable precursor for g-C3N4 catalyst synthesis and as a sacrificial agent for green hydrogen production via photoreforming. Platinum-modified graphitic carbon nitride catalysts were synthesized and evaluated using pure lactic acid and commercial PLA waste under solar-simulated irradiation. Results identified C3N4-NaOH-Pt as the most active material, while the simultaneous one-pot depolymerization/photoreforming of macroscopic PLA fragments exhibited a peak H2 production rate of 1.5 mmol·h−1·g−1, remarkably surpassing both the pure monomer model and pre-depolymerized solutions. This enhanced performance is tentatively attributed to a “controlled release” mechanism that prevents catalyst surface saturation and minimizes light scattering effects inherent to fine powders. The study concludes that maintaining the macroscopic integrity of PLA waste provides a strategic advantage for chemical reforming by eliminating energy-intensive grinding and pretreatment. Future research into diverse operational and chemical parameters, including temperature and base-addition strategies, will be essential for scaling solar-driven upcycling technologies.

Clean Technologies doi: 10.3390/cleantechnol8040103

Authors: Juliana Abraham Anthony Tesori Washington Braida Tsan-Liang Su Christos Christodoulatos

The production of Nitrocellulose (NC) generates wastewater containing insoluble fines which can be solubilized via alkaline hydrolysis (AH). However, this process yields effluents with high NO2-N and NO3-N concentrations (3:1 ratio), opening the possibility of further treatment and nutrient recovery. This study investigated the ecotoxicity and algae-based treatment potential of post-AH liquor as a proof of concept for wastewater management. Ecotoxicity assessments such as microalgal and Microtox® bioassays showed 30% toxicity (corresponding to 240–270 mg NO2-N/L and 100 mg NO3-N/L) and a 15 min EC50 of 331–399 mg NO2-N/L and 133–146 mg NO3-N/L, respectively. Additional studies on toxicity identified nitrite (NO2−) as the primary toxicant, inhibiting the freshwater microalga Scenedesmus obliquus at concentrations higher than 60 ± 5 mg N/L. Furthermore, higher toxicity was observed in the presence of sodium and nitrate. Consequently, growth screening tests using synthetic liquors (20–300 mg TN/L, with NO2-N:NO3-N ratio 3:1) compared S. obliquus against the marine microalga Nannochloropsis salina, revealing that S. obliquus thrived at concentrations below 160 mg N/L, whereas N. salina performed poorly. System efficiency was shown to be highly dependent on the initial nitrogen load; S. obliquus achieved 60% removal at 200 mg/L total nitrogen (3:1 NO2-N:NO3-N), whereas efficiency reached 99% at concentrations less than or equal to 100 mg/L within seven days. Nitrogen removal rates peaked at 15 mg/(L·day) (at <160 mg TN/L), a result validated through scale-up experiments using both monoculture and a consortium with post-AH liquor. These preliminary findings demonstrate a promising two-step chemical and biological treatment strategy for NC wastewater, which assimilates hazardous inorganic nitrogen into valuable algal biomass for potential energy production.

Clean Technologies doi: 10.3390/cleantechnol8040102

Authors: Nestor F. Guerrero-Rodríguez Francisco A. Ramírez-Rivera Rubén D. Ramos Ciprian

Green hydrogen is commonly assessed as a renewable fuel or long-duration storage option, but its value as a critical-load restoration resource remains less developed, particularly when produced from curtailed renewable electricity. This study develops a planning-oriented framework to assess green hydrogen for critical-load restoration by linking renewable curtailment, proton-exchange membrane electrolysis, hydrogen storage, fuel-cell reconversion, critical Energy Not Served (ENS) reduction, economic valuation, and carbon-footprint savings. The framework is applied to the Dominican Republic power system as a representative insular case with rapid renewable expansion and limited flexibility. Using monthly preliminary real-operation reports from OC-SENI, the reference case considers 196.46 GWh/year of curtailed non-conventional renewable electricity in 2025, producing 3.78 kt H2/year and 65.5 GWh/year of recoverable electricity. Under the reference screening assumptions, a 25 t H2 storage module would provide 433.29 MWh of usable electricity, fully covering 6 h and 12 h restoration windows for the 30 MW illustrative critical-load case and reducing critical ENS by 60.2% during a 24 h event. The recovered electricity could avoid 43.5 ktCO2/year under the SENI combined-margin grid-displacement case, with higher avoided operational emissions under the diesel-backup displacement sensitivity.

Clean Technologies doi: 10.3390/cleantechnol8040101

Authors: Stefan Cristian Galusnyak Letitia Petrescu Florina-Augusta Baldean Calin-Cristian Cormos

The growing demand for acrylic acid, driven by its widespread use in polymers and specialty chemicals, raises concerns regarding the environmental impact of its conventional fossil-based production. In this context, the present study evaluates the techno-environmental performance of a glycerol-based acrylic acid route compared to the conventional propylene pathway. Process simulations were carried out using CHEMCAD for an annual capacity of 50,000 tons. The environmental impact is assessed through Life Cycle Assessment (LCA) methodology and LCA for Experts software, following the ReCiPe 2016 (H) impact method. The results show that the glycerol-based route requires higher raw material input (1.90 kg/kg acrylic acid) than the propylene pathway (0.84 kg/kg acrylic acid), yet generates slightly lower liquid wastes (3.25 kg/kg acrylic acid vs. 3.60 kg/kg acrylic acid). From an environmental standpoint, the glycerol route performs better in 12 of 16 impact categories. The conventional process is dominated by the propylene supply chain, contributing up to 62% of the global warming impact, while electricity demand ranks second in the glycerol-based route. Scenario analysis based on future European electricity mixes (EU-2030 and EU-2050) further reduces climate and fossil depletion impacts, although with increased mineral resource use. Overall, the results highlight the potential of glycerol as an alternative feedstock and the key role of electricity sourcing.

Clean Technologies doi: 10.3390/cleantechnol8040100

Authors: Lakshmi Shiva Shankar Tibor Cseke Zoltan Weltsch

Efficient thermal management is a critical constraint for the performance, safety, and lifetime of electric vehicle (EV) batteries, particularly under transient high-power operation, where conventional dielectric coolants remain limited by the absence of thermal buffering. This Perspective examines PCM–dielectric hybrid coolants as a multiphase electro-thermal-fluid system, in which microencapsulated phase-change materials provide localized latent heat storage within a circulating insulating medium. Rather than proposing a new material concept, the work establishes a system-level engineering framework that links material properties, transport behavior, and electrical constraints to practical implementation. Key challenges, including dispersion stability, capsule durability under coupled stresses, dielectric reliability in heterogeneous media, and rheological limitations, are analyzed alongside quantitative design envelopes and validation pathways. A structured roadmap is presented, spanning multiphysics modeling, accelerated material qualification, system-level testing, and industrial integration, supported by techno-economic and lifecycle considerations.

Clean Technologies doi: 10.3390/cleantechnol8040099

Authors: Uroš Durlević Vladimir Malinić Dejan Doljak Dragana Valjarević Marko Sedlak Dušica Jovanović Milan Milenković Aleksandar Kovjanić Marko V. Milošević Slavica Malinović-Milićević Aleksandar Valjarević

Due to increasing demand and consumption of electricity, as well as the need to decarbonize and mitigate climate change, solar energy is an important factor in the transition to emission-free energy sources. This study focuses on identifying the most suitable locations for the construction of large solar photovoltaic (PV) power plants while respecting environmental, economic, and technical standards. The study area covers the mainland part of Southeastern Europe (796,039 km2), including the following countries: Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, North Macedonia, Albania, Greece, Bulgaria, Romania, Moldova, and Türkiye. Using geographic information systems (GIS) and remote sensing methods, nine factors (topographic, climatic, hydrological, ecological, vegetation, and anthropogenic) were analyzed with a spatial resolution of 100 m. A fuzzy analytic hierarchy process (F-AHP) pairwise comparison matrix was constructed to quantify the relative importance of the selected criteria. The F-AHP weighting results indicate that photovoltaic output (17.9%) and land use (15.7%) are the most important among the evaluated criteria. The results show that 6.7% of Southeastern Europe is very highly suitable for installing solar PV plants, with the most suitable areas located in Moldova (14.5%) and Greece (10.5%). Through spatial analysis of the final results, 24 of the most suitable locations for large-scale solar PV power plant development were identified, with a potential to generate approximately 30.2 TWh of electricity annually. In such a scenario, the forecast indicates that 24 large-scale solar power plants would supply electricity to more than 6.7 million households, corresponding to over 17 million inhabitants. The final spatial patterns provide decision-makers at the international level with a significantly more effective basis for planning solar energy development in order to increase the share of green energy and clean technologies in this part of Europe.

Clean Technologies doi: 10.3390/cleantechnol8040097

Authors: Guillermo Valencia Juan Córdoba César Isaza-Roldan

The residential sector accounts for a significant portion of global energy demand, which can be met through sustainable alternatives such as solar energy. This study evaluated the energy, exergy, environmental, and exergy-sustainability performance of three waste heat recovery configurations (double-loop organic Rankine cycle—DORC, Kalina cycle—KC, and organic Rankine cycle—ORC) coupled to a supercritical CO2 Brayton cycle with intercooling and reheating, designed to meet the demand of a residential complex of 120 homes in the Colombian Caribbean region, built with four different materials, using a concentrated solar power tower as the heat source. Mass, energy, and exergy balances were performed, along with a life cycle analysis, sizing the systems to supply a cooling load of 133 kW. The results show that the three configurations meet the required demand, with energy efficiencies above 50%: sCO2-DORC (51.7%), sCO2-ORC (51.61%), and sCO2-KC (51.32%), with a maximum exergy efficiency for sCO2-DORC (24.3%). The environmental analysis indicates that the construction phase accounts for more than 95% of total emissions. Overall, the results confirm the viability of these configurations for residential applications, promoting the integration of renewable energies and supporting the regional energy transition.

Clean Technologies doi: 10.3390/cleantechnol8040098

Authors: Bao Luo Ayiguzhali Tuluhong Feng Wang Ailitabaier Abudureyimu

Large-scale photovoltaic (PV)–hydrogen production systems are increasingly regarded as a promising solution for mitigating renewable energy curtailment and supporting the transition toward low-carbon energy systems. However, when connected to weak grids, such systems often suffer from insufficient voltage–frequency support capability and pronounced Direct current (DC) bus voltage fluctuations, which limit their operational stability and practical deployment. To address these challenges, this paper proposes a dual virtual motor coordinated control strategy for PV-based hydrogen production systems, integrating a grid-forming virtual synchronous generator (VSG) with a virtual DC motor (VDCM). By exploiting the complementary dynamic characteristics of grid-side converters and hydrogen production loads, the proposed approach enhances grid support capability while simultaneously providing inertia and damping to the hydrogen production DC bus without relying on additional physical energy storage. Dynamic response analysis is conducted to investigate the influence of virtual inertia and damping parameters on system stability. Simulation results under weak-grid conditions demonstrate that the proposed strategy effectively improves frequency and voltage support performance and significantly suppresses DC bus voltage fluctuations during load and power disturbances. The proposed control framework offers a practical and scalable solution for improving the operational robustness of PV–hydrogen production systems, contributing to the reliable integration of renewable energy and the development of green hydrogen infrastructure.

Clean Technologies doi: 10.3390/cleantechnol8040096

Authors: Konstantin R. Frolov Valentina P. Zvereva

The Baleysky gold deposit in Eastern Transbaikalia is a classic example of the long-term environmental legacy of gold mining. The cessation of industrial wastewater discharge in 1995 led to the accumulation of more than 3 million m3 of acidic water with high concentrations of heavy metals and metalloids. These waters contain concentrations many times higher than the maximum permissible levels for fishery waters (Mn up to 6594, Al—1473, Zn—486, and Cu—414), posing a significant threat to the ecosystem of the Unda River and the health of the local population. The aim of this study was to evaluate the effectiveness of the artificial geochemical barrier method for treating such waters under laboratory conditions. Column experiments were conducted using local soil and the commercial carbonate sorbent taurite at a sorbent-to-filtrate ratio of 1:5. Taurite demonstrated a significantly higher sorption capacity than soil, substantially reducing the concentrations of As, Cd, Pb, Al, Mn, Fe, Zn, and Cu and raising the pH from 2.90 to 7.96–8.03. Although health risks associated with both carcinogenic (CR) and non-carcinogenic effects (HI) decreased significantly after treatment with taurite, residual risk levels remained unacceptably high (CR ≈ 10−3, HI > 1). The results show that engineered geochemical barriers have great potential for reducing anthropogenic contamination at abandoned mining sites, although further optimization of this technology is necessary to achieve compliance with regulatory requirements.

Clean Technologies doi: 10.3390/cleantechnol8030095

Authors: Carlos Cobo-Ceacero María Cotes-Palomino Lázaro Márquez-Montes Carmen Martínez-García Francisco Troyano-Pérez Ana López

The valorization of industrial mining and organic wastes in construction materials constitutes a key strategy for reducing the environmental impact of the sector. In this context, the present study aims to evaluate the sustainability of innovative Artificial Lightweight Aggregates (ALAs) manufactured from mixtures of inorganic industrial wastes—such as granite and slate cutting sludge and aggregate washing sludge—together with organic wastes, like cork dust, coffee grounds, and olive pits. The methodology included a Life Cycle Assessment (LCA), considering different waste compositions and manufacturing conditions. The results show that the developed ALAs exhibit favorable environmental performance as their bulk density decreases, with an overall environmental impact lower than that of conventional lightweight aggregates made from expanded clay, achieving a reduction in the carbon footprint of up to 7%. Likewise, the comparative analysis reveals that the process stage with the greatest environmental impact is the heat energy required during the sintering stage in the rotary kiln, which in some cases accounts for more than 90% of the total impact. In summary, the results demonstrate the feasibility of obtaining ALAs manufactured solely from waste with a lower carbon footprint compared to traditional expanded clay aggregates. Furthermore, the study highlights that the process stages with the highest contributions to environmental impact are the transport of raw materials and the high-temperature sintering of the ALAs in the rotary kiln. Thus, their production from waste contributes to the valorization of by-products, fostering circular economy strategies and supporting decarbonization processes within the construction sector.

Clean Technologies doi: 10.3390/cleantechnol8030094

Authors: Stepan E. Sokolov Pavel O. Tokarev Valentina K. Grudkovskaya Ivan S. Levin Maxim G. Shalygin Evgenia A. Grushevenko

Membrane separation is an efficient approach for volatile organic compound (VOC) recovery from industrial off-gases due to its low energy consumption, compact design, and operational simplicity. Membrane-based VOC recovery critically depends on the membrane material, which must exhibit high VOC permeability and selectivity under mixed-gas conditions. In this study, novel highly selective membranes for VOC removal based on polydecylmethylsiloxane (PAMS-10) were synthesized using both polydimethylsiloxane and various α,ω-dienes as cross-linkers: 1,7-octadiene (OD), 1,9-decadiene (DD), and 1,11-dodecadiene (DdD). The influence of cross-linker concentration and length on mechanical, structural, sorption, and transport properties was examined extensively. The combination of three independent experimental methods (time-lag, vapor permeation, and in situ spectroscopic ellipsometry) revealed that increasing α,ω-diene concentration and decreasing its length led to a reduction in the diffusivity and permeability of permanent gases, gaseous hydrocarbons, and VOC vapors. For VOC/N2 separation, the slightly cross-linked OD-1 membrane and the DdD-5 membrane, cross-linked with long 1,11-dodecadiene, demonstrated outstanding mixed-gas selectivities of 950/921/314/840 and 940/1084/233/1106 for toluene/n-octane/i-octane/n-butyl acetate, respectively. Notably, the DD-5 membrane, cross-linked with 1,9-decadiene, matching the length of the PAMS-10 side chain substituent, exhibited the best mechanical properties and mixed-gas selectivity comparable to the ideal selectivity, a unique behavior attributed to optimal supramolecular organization.

Clean Technologies doi: 10.3390/cleantechnol8030093

Authors: Aminata Sarr Y. M. Soro Lamine Diop Alain K. Tossa Badza Kodami P. Romaric Christian Samayouga

Agrivoltaics is a promising technique, especially in view of the rapid population growth associated with the expansion of cultivated areas to satisfy the food demands of the population, and the increase in solar power plants, which require considerable space to supply the population with energy. Thus, the transition from agricultural to agrivoltaics systems and the transition from PV power plants to agrivoltaics systems can enable more efficient use of land for energy and agricultural production. However, the configuration of agrivoltaics systems, namely panel elevation, spacing between panels and between rows of panels, and panel size, defines the amount of material used. As a result, configuration can have a major impact on the environment. The aim of this study is to highlight the environmental impact from converting 1 ha of land used entirely for agricultural production to 1 ha of an agrivoltaic system, and from converting 1 ha of land used entirely for solar photovoltaic energy production to 1 ha of an agrivoltaic system through a life cycle assessment. Three different configurations of agrivoltaics systems are considered to assess the environmental potential of agrivoltaics configurations. This analysis is performed with SimaPro 9.4 software, using the ReCiPe Midpoint (H) method and the Eco-invent database. The study determined impacts on global warming, stratospheric ozone depletion, ionizing radiation, ozone formation, mineral resource scarcity, fossil resource scarcity, water consumption, and land use through the determination of the Land Equivalent Ratio (LER). The results show that impacts are highest for PV power plants, followed by the agrivoltaic system with the largest PV panels for all indicators, except for stratospheric ozone depletion, where impacts are highest for agrivoltaics and agricultural use systems. The results of the land evaluation showed that the agrivoltaic system Case 3 gave the best performance, with a Land Equivalent Ratio of 148.7%.

Clean Technologies doi: 10.3390/cleantechnol8030092

Authors: Novita Wiwoho Doonyapong Wongsawaeng Phannee Saengkaew Phachirarat Sola Deni Swantomo

A predictive gate-to-gate life cycle assessment (LCA) of plasma-assisted ammonia synthesis at TRL 4 is presented according to ISO 14040/44 standards. General plasma-assisted synthesis was evaluated through a mini-review‚ sensitivity analysis‚ and predictive LCA. The specific DBD needle-to-plate configuration LCA is performed using previously published experimental data. Two distinct scenarios were investigated. In the literature-based baseline scenario derived from sensitivity analysis, electricity consumption was 533 kWh/kg NH3, giving a carbon footprint of 26.65–639.60 kg CO2-eq/kg NH3; electricity contributed 98.5% of total emissions, and impacts remained about 2.05 times higher than conventional Haber–Bosch. In contrast, the experimental DBD case study required 63,450 kWh/kg NH3, showing reactor efficiency as the dominant driver of environmental performance. The BCS (≈1.39 kWh/kg NH3) suggests that optimized plasma systems could potentially surpass conventional ammonia synthesis in energy efficiency. The environmental performance of plasma-assisted ammonia synthesis is affected by NH3, NOx, N2O, and hydrogen emissions due to impacts on climate, air quality, water systems, and biodiversity. Future improvements may come from reactor and electrode optimization, catalyst integration, alternative plasma sources, and better process and heat integration, although deployment will likely depend on major efficiency gains and may be limited to niche decentralized applications.

Clean Technologies doi: 10.3390/cleantechnol8030090

Authors: Silvia D’Eusebio Pietro Caramia Antonio Caporusso Matteo Radice Antonino Biundo Isabella Pisano Gennaro Agrimi

Waste cooking oils (WCO) are large-scale residual streams from domestic and industrial food processing. Their improper disposal poses severe environmental risks, yet their integration into the oleochemical sector offers a strategic opportunity for the green transition by substituting fossil-based feedstocks. This systematic review provides a comprehensive assessment of WCO valorization as a sustainable precursor for high-value products, specifically biopolymers, bioplasticizers, and biolubricants. The study followed the PRISMA 2020 guidelines, searching PubMed, Scopus, and MDPI databases (up to September 2025). The search strategy utilized combinations of keywords present in the title. Inclusion criteria focused on peer-reviewed chemical and biotechnological conversion pathways published in English within the last decade. Studies addressing biofuel production, patents, and review were excluded. Screening, data extraction, and qualitative risk of bias assessment, centered on experimental reproducibility and reporting transparency, were performed independently by multiple reviewers. From an initial pool of 2637 records, 87 studies met the eligibility criteria. The analysis reveals that polyhydroxyalkanoates (PHAs) represent the most extensively researched pathway, followed by WCO-derived epoxides and innovative biolubricant formulations. While several studies report high conversion yields under optimized conditions, the transition from bench-scale to industrial implementation remains hindered by the heterogeneous composition of WCO and a lack of standardized pre-treatment protocols. WCO valorization shows transformative potential for the circular economy, offering a dual benefit of waste mitigation and sustainable material synthesis. However, future research must address scalability challenges and feedstock variability. This review identifies emerging trends and provides a roadmap for the industrial adoption of WCO-based processes in the framework of clean technologies.

Clean Technologies doi: 10.3390/cleantechnol8030091

Authors: Matz Dietrich Thomas Bacquart Abigail Morris Shirin Khaki Etienne Basset Mathilde Rizand Martine Carré Claire Blondeel Nathalie Chramosta Alexander Kvasnicka Pierpaolo Modugno Ziyin Chen Christian Spitta Harry Hoster

Taking spot samples at hydrogen refuelling stations (HRSs) and performing offline analysis in laboratories is currently the only way to achieve hydrogen fuel compliance at HRS (meet the ISO 14687:2025 standard or EN 17124:2022 in Europe). Currently, different sampling strategies are defined in ISO 19880-9:2024 (Annex A–C) and implemented in different parts of the world (EU, Japan, USA). The differences in conducting the sampling potentially influence the hydrogen samples; therefore, there is a need to compare the different sampling strategies. Comparative sampling studies are required to evaluate the equivalence of sampling methodologies and support the standardisation of hydrogen fuel sampling. This study provides a systematic comparison of five European sampling systems with different sampling strategies under real and defined HRS operation conditions. The results show that the issue of representative sampling is more complex than initially assumed and that there is an interdependence of sampling device and HRS configuration, respectively.

Clean Technologies doi: 10.3390/cleantechnol8030089

Authors: Joel Awinzure Agumah Xiaojun Liu Laura André Camille Auneau Sophie Thibault Chrystelle Bureau Sabrina Guérin Vincent Rocher Carlyne Lacroix Olivier Chapleur Ariane Bize Céline Roose-Amsaleg André Pauss Thierry Ribeiro

The accumulation of intermediate products, particularly volatile fatty acids (VFAs) like propionic acid (HPr) or its dissociated form, can inhibit biogas production during anaerobic digestion (AD) at low concentrations. Knowledge about the response of microorganisms to VFA inhibition can help control the digesters. In this study, we aimed to determine how sodium propionate (NaPr) inhibits the AD of municipal sewage sludge by identifying shifts in the microbial community. Four 5 L reactors were operated in semi-continuous mode using sewage sludge and then loaded with different levels of NaPr. The reactors operated at 37 °C with two hydraulic retention times. The results show that there was no apparent inhibition of biogas production at NaPr loading up to 20.3 mmol·L−1. However, moderate inhibition was observed at 81 mmol·L−1, corresponding to an approximate 10% decrease in methane production, while a ≈40% decrease in methane production was observed at 135.3 mmol·L−1. Sequencing analysis revealed that the community composition was dominated by Bacillota, Bacteroidota, Proteobacteria, Chloroflexi, and Cloacimonadota, with Halobacterota and Euryarchaeota as the main archaeal groups. PERMANOVA revealed incubation time as the primary driver of community structure, followed by NaPr concentration. Elevated NaPr levels resulted in a decline in Methanothrix and Methanobrevibacter and promoted distinct syntrophic propionate-oxidizing bacteria (SPOB).

Clean Technologies doi: 10.3390/cleantechnol8030088

Authors: Luis Angel Iturralde Carrera Daniel Fernández Navarro Yoisdel Castillo Alvarez Ariadna Yaneli Reséndiz-Jaramillo Carlos D. Constantino-Robles Leonel Díaz-Tato Miguel Angel Cruz-Pérez Juvenal Rodríguez-Reséndiz

Anaerobic digestion is a viable pathway to mitigate environmental impacts from swine manure in tropical regions while contributing to circular economy strategies. However, no standardized or integrated framework currently exists that simultaneously quantifies the closure of energy, material, carbon, nutrient, and water loops at the farm scale. This research presents the techno-economic design and environmental assessment of a covered, mechanically agitated lagoon biodigester for a 10,000-head swine fattening module located in Matanzas, Cuba. The system is sized by integrating hydraulic, thermal, and structural parameters, and its economic viability is assessed through Net Present Value (NPV = $1.09 million), Internal Rate of Return (IRR = 32%), and a payback period of approximately three years. A comparative screening-level life cycle assessment shows that biogas-based electricity generation substantially reduces impacts on climate change, air quality, and fossil fuel scarcity compared with conventional diesel-based generation, with trade-offs in eutrophication and ecotoxicity. As a key methodological contribution, five quantitative circular economy indicators are proposed and calculated: the Energy Self-Sufficiency Ratio (ESSR = 1.71), the Waste Valorization Index (WVI = 0.91), the Decarbonization Index (DCI = 6.7), the Fertilizer Substitution Rate (FSR = 16.3 t N year−1), and the Water Closure Factor (WCF = 1.30). These indicators show that the system achieves a 71% net energy surplus, valorizes over 90% of the input mass, avoids 6.7 times more emissions than it generates, replaces synthetic fertilizers, and returns more water than it consumes. The findings provide quantitative evidence that the convergence of mesophilic operation without auxiliary heating, high carbon intensity of the power grid, and availability of agricultural land enhances circularity performance in tropical covered lagoon bioreactors, and the proposed integrated indicator framework, aligned with ISO 59020:2024, provides a reproducible and transferable methodological basis for the comparative assessment of anaerobic digestion systems for livestock waste.

Clean Technologies doi: 10.3390/cleantechnol8030087

Authors: María Maldonado-Sada Carlos Calles-Arriaga José Castillo-Robles Jacinto Treviño-Carreon Enrique Rocha-Rangel

In this work, ZnO nanoparticles were synthesized via a plant-mediated green route using Prosopis tamaulipana extract as a reducing and stabilizing agent and subsequently modified with silver to obtain Ag-modified ZnO powders. Structural and morphological characterization techniques confirmed the formation of nanocrystalline ZnO with a hexagonal wurtzite structure, submicrometric agglomerates composed of nanosized primary particles and a high degree of phase purity, indicating the effectiveness of the synthesis approach. The photocatalytic performance of the Ag-modified ZnO materials was evaluated under natural solar irradiation using methylene blue as a model organic contaminant in aqueous solution. Visual observations, together with absorbance, temperature and electrical conductivity measurements, demonstrated an effective and progressive degradation of the dye over a 5 h irradiation period. The observed increase in electrical conductivity under illumination was associated with enhanced charge carrier generation and improved separation efficiency, as well as the formation of reactive oxygen species, promoted by the presence of Ag as an electron sink. These results confirm that green-synthesized Ag-modified ZnO nanoparticles exhibit enhanced photocatalytic activity and are promising multifunctional materials for sustainable water sanitation applications.

Clean Technologies doi: 10.3390/cleantechnol8030086

Authors: Carlos Luna Emanuel Araújo Pedro Nicácio Elieber Bezerra Débora Schmitz Bluma Soares Renate Wellen Edcleide Araújo

This study aims to develop sustainable conductive nanocomposites based on poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends reinforced with multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (G), focusing on their multifunctional performance. The novelty lies in the production of hybrid nanocomposites based on PLA/PCL blends with MWCNT/G using conventional industrial processing techniques, enabling the development of eco-friendly nanocomposites with tailored electrical, mechanical, and electromagnetic properties. The nanocomposites were prepared by twin-screw extrusion followed by injection molding. Rheological, scanning electron microscopy (SEM), mechanical, thermal, thermomechanical, electrical conductivity, and electromagnetic shielding properties were systematically evaluated. From a rheological perspective, the PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites exhibited a plateau at low frequencies, associated with the formation of a percolated network. This was confirmed by the significant increase in electrical conductivity and electromagnetic shielding response. The morphology observed by SEM showed a refinement of the PCL phase in the PLA matrix with the incorporation of MWCNT. The PLA/PCL/MWCNT/G (4/2 parts per hundred resin, phr) nanocomposite showed a 309% increase in impact strength compared to neat PLA, while maintaining the heat deflection temperature (HDT). The elastic modulus exceeded 2300 MPa and accelerated the crystallization process by more than 15 °C compared to PLA, which makes it important to reduce injection molding time. Additionally, it exhibited the highest electrical conductivity level, around 6.79 × 10−5 S/cm, which resulted in improved electromagnetic shielding performance in the 8.2–18 GHz range, highlighting the synergistic effect between 1D and 2D fillers. The developed PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites demonstrate potential for antistatic applications, combining sustainability with multifunctional performance and industrial scalability.

Clean Technologies doi: 10.3390/cleantechnol8030085

Authors: Fidan Eser Şule Satoğlu

This study investigates how the hydrogen supply chain should be designed under alternative carbon tax scenarios to decarbonize heavy-duty freight transportation. A bi-objective, multi-period optimization model is developed to minimize the total daily system cost while constraining CO2 emissions using the Augmented ε-constraint approach, thereby revealing the trade-off between economic and environmental objectives. The model was applied to Türkiye’s heavy-duty transportation sector and solved under zero, moderate, and aggressive carbon tax scenarios. The results show that the levelized cost of hydrogen (LCOH) ranges from 2.06 to 14.06 $/kg H2. High carbon pricing increases the LCOH by 29.06% in hybrid designs, while raising the renewable energy share from 2.04% to 46.97% in centralized supply chains. Sensitivity analysis reveals that a ±20% variation in electrolyzer-based production costs does not alter the network topology but shifts the LCOH between 13.10 and 15.02 $/kg H2 in emission-focused solutions. The findings indicate that in renewable-energy-based decentralized structures, higher carbon tax policies primarily increase the LCOH. Still, the overall technology mix and network topology remain largely unchanged compared to the no-tax case. However, in centralized supply chains, carbon pricing affects both the energy sources and selected technologies. By integrating Türkiye’s 2030–2053 policy milestones into a multi-period framework, this study distinguishes itself by providing a comprehensive, multi-period planning framework tailored to the economic and logistical realities of developing countries. Unlike existing models, our approach quantifies how evolving carbon tax trajectories decisively drive infrastructure investment by analyzing the direct impact of different tax levels on the operational and strategic decisions of heavy-duty transport. This research represents the first joint assessment of carbon tax policy instruments and the evolution of long-term hydrogen supply chains, offering a decision-making framework for policy-driven energy transitions in similar emerging economies.

Clean Technologies doi: 10.3390/cleantechnol8030084

Authors: Hossein Yousefi Rizi Donghoon Shin

Ammonia, as a carbonless carrier of energy, presents considerable potential for hydrogen storage and production, as well as for power generation, thanks to its high energy density and relatively easy transportability. However, the practical adoption of ammonia in combustion systems faces major stability challenges—chiefly its low reactivity, slow laminar burning velocity, narrow flammability envelope, and high ignition temperature. These attributes increase the risks of flame instability, misfire, and incomplete combustion, which, in turn, can elevate levels of unburned ammonia and greenhouse gas emissions such as NOx—posing significant health and climate concerns. Stable ammonia combustion demands optimization of several interrelated factors: the air–fuel equivalence ratio, flame temperature, flow regime, and combustor design are critical for maintaining reliable operation. Particularly pivotal is the control of the air–fuel equivalence ratio; excessively lean conditions can trigger flameout. Modern systems utilize real-time monitoring of flame and exhaust properties to diagnose and prevent instabilities. Advanced combustion strategies, such as transitioning to diffusion or flameless (MILD) regimes, substantially expand the stable operating window, especially under lean conditions. Overall, sustaining stable ammonia combustion is essential for maximizing efficiency and emission control, and integrating aftertreatment (deNOx) technologies is crucial for sustainable, clean-energy implementation.

Clean Technologies doi: 10.3390/cleantechnol8030083

Authors: Chenshu Ma Lizong Sun Shu Kang

Soil cadmium (Cd) pollution has emerged as one of the key environmental issues threatening the safety of agricultural products worldwide, yet clean and low-cost intervention strategies that reduce Cd accumulation in edible crops without disrupting agricultural production remain scarce. Grafting onto tolerant rootstocks represents an emerging clean agronomic technology that achieves in situ Cd risk reduction within a single growing season. However, the molecular mechanisms by which rootstocks regulate scion phenotypes remain poorly understood. MicroRNAs (miRNAs) act as critical long-distance signals in plants, yet their roles in rootstock-mediated growth promotion and Cd reduction remain largely unclear. In this study, we used Solanum torvum as rootstock and purple eggplant (Solanum melongena) as scion to investigate growth, fruit quality, Cd accumulation, and miRNA-mediated regulatory mechanisms. Grafting significantly increased plant height (by 18%), stem diameter (by 12%), and yield without obvious effects on fruit quality. Under Cd stress, the Cd content in grafted eggplant fruits was reduced by 76%, whereas leaf potassium (K), calcium (Ca), and magnesium (Mg) contents were elevated by 21%, 17%, and 10%, respectively. High-throughput sequencing and quantitative real-time polymerase chain reaction identified five key differentially expressed miRNAs, including miR164a and miR166b, four of which were related to Cd stress. Gene Ontology (GO) enrichment analyzes that their target genes were mainly involved in hormone signal transduction and ion transport. Further validation suggested that grafting improved growth and reduced Cd accumulation by regulating genes of the NAC, SPL, and HD-ZIP III families. These results suggested that suitable rootstocks can enhance crop productivity and reduce toxic metal accumulation in edible parts through miRNA-mediated regulation.

Clean Technologies doi: 10.3390/cleantechnol8030082

Authors: Maroš Begáni Miriama Javorská Lucia Bednárová Mário Molokáč

The rapid expansion of the hydrogen economy has intensified the need for accessible production technologies. This study presents a comparative assessment of two next-generation hydrogen production systems showcased at the Hydrogen Expo Hamburg 2025: the containerised HyPro electrolyser and the modular Enapter EL 4.1. The analysis focuses on their technical specifications, operational philosophies, and indicative costs. Data were gathered through technical consultations with exhibitors and catalogue analyses. The evaluation highlights key differences in system architecture, production capacity, and installation requirements within academic research environments. The results demonstrate how suitability depends on the intended scale of application, contrasting a laboratory-ready modular approach with an industrial-oriented turnkey configuration. This study provides practical insights to support universities and research institutions in selecting hydrogen production equipment that aligns with their specific infrastructural and budgetary conditions.

Clean Technologies doi: 10.3390/cleantechnol8030080

Authors: Ioannis Kontodimos Christos Evaggelou Nikolaos Margaritis Panagiotis Grammelis Maria A. Goula

This study proposes an integrated and more circular management approach, grounded in the principles of sustainable and green chemical processes, for the food waste leachates management, combining the assessment of biomethane production potential via anaerobic digestion with the evaluation of value-added compound recovery through extraction processes. The food waste leachates were characterized, while total carotenoid profile and total phenolic content were quantified using liquid–liquid extraction with mixed organic solvents. An HS-SPME coupled with GC–MS was employed to identify volatile organic compounds present in the leachates. Prior to the extraction procedure, D-limonene exhibited the highest abundance among identified volatiles. Crucially, the subsequent solvent extraction is highly likely to have effectively removed this inhibitory terpene from the liquid matrix. Extracted leachates exhibited a total carotenoid content of 0.64 mg/100 g and a total phenolic content of 127.0 μg/g, acting as preliminary indicators of significant potential for recovery and utilization in pharmaceutical and cosmetic applications. Biomethane potential tests were conducted in laboratory-scale anaerobic bioreactors using both raw food waste leachate and extracted food waste leachate. Comparable biomethane yields were obtained for both substrates, with FWL yielding 442.5 NmL/g VSadded and FWLextr yielding 452.2 NmL/g VSadded. These results demonstrate that the liquid–liquid extraction of value-added compounds does not adversely affect biomethane production from food waste leachates enabling the recovery of valuable by-products.

Clean Technologies doi: 10.3390/cleantechnol8030081

Authors: Alexander A. Greish Pavel V. Sokolovskiy Elena D. Finashina Olga P. Tkachenko Timur R. Khabibullin Svetlana B. Polikarpova Vladislav Yu. Kirsanov Valeriy E. Ponomarev Artem A. Medvedev Leonid M. Kustov

The adsorption of H2S impurity in the gas flow on carbon adsorbents produced from coconut shells and sugarcane bagasse was studied. The runs were carried out in pulse mode. An original chromatographic method for determining the degree of H2S absorption on carbon adsorbents has been developed, which makes it possible to determine the amount of absorbed H2S in air and water environments. The results obtained show that the successive treatment of carbon adsorbents first with a solution of a strong oxidizer (HNO3, KMnO4) and then, after washing, with an alkali solution (KOH) leads to a sharp increase in the amount of H2S adsorbed. The efficiency of H2S absorption on the obtained adsorbent reaches 85.5%, which corresponds to 27.7 mg/g H2S and is comparable to the results obtained on commercial coconut carbon (CAU). The data allow one to conclude that the rise in the H2S adsorption on the carbon sorbents studied can be due to the increase in the micropores’ volume in the activated carbon, as well as the formation of surface functional groups containing an alkali metal (i.e., C-OK, C-COOK) that promotes irreversible chemisorption of H2S impurity on the carbon adsorbent. The absorption of H2S occurs through the chemisorption mechanism, which is confirmed by IR spectroscopy data.

Clean Technologies doi: 10.3390/cleantechnol8030079

Authors: Vítor João Pereira Domingues Martinho

Topics related to renewable and sustainable energy have been addressed by several scientific studies over the last few decades. Nonetheless, it is important to highlight what has already been done by the scientific community and what remains to be done in these fields to provide more insights for stakeholders, including policymakers, researchers, and economic operators. The literature survey showed that there are still gaps to be considered in the literature and novelties to be brought through different approaches, particularly those that take into account the several dimensions of these issues. From this perspective, this research aims to present the dimensions of renewable and sustainable energy explored in scientific documents, benchmarking past and future pathways in these domains. To achieve these objectives, a bibliometric analysis (focusing on scientific maturity) was carried out separately across different dimensions associated with this topic (this is one of the novelties of this study). Additionally, a targeted literature analysis based on bibliometric analysis was done, considering the most relevant documents. This research adopts a broad perspective in order to capture the context of energy transition, clean energy, and low-carbon development. The findings obtained show that the subject of renewable and sustainable energy has several topics and subtopics with different dynamics. Within these subtopics, it is worth mentioning the following: solar and wind energy are almost in the saturation phase (85.1% of potential development has already occurred); bioenergy, biomass, and hydroelectric power are at the beginning of the maturity phase (59.7% progress to saturation); tidal and wave energy are in the middle of the maturity phase (71.5% progress to saturation); green hydrogen and clean energy are in the saturation phase (99.0%); renewable energy and sustainable development goals are in the saturation phase (99.0%), and energy policy and technological innovation in renewable energy are in the middle of the maturity phase 68.0%). These results reflect the overlap between different topics rather than the individual scope of each field of research.

Clean Technologies doi: 10.3390/cleantechnol8030078

Authors: Xiaoyan Le Mengmeng Shen Ziyi Liao Zhongyuan Zhu Hao Niu Kai Luo Xidong Shi Qiaoli Wang

Purified terephthalic acid (PTA) is an extremely important bulk organic raw material; it plays a central connecting role in the PX–PTA–polyester industry chain, while its significant carbon intensity remains poorly quantified. Through process-level life cycle assessment (LCA) based on in situ industrial data, this study establishes a comprehensive material-energy inventory for PTA production. The results show that the total greenhouse gas (GHG) emissions of the entire PTA process reached 1600.9 kg of CO2 eq·t−1, exceeding those of common primary chemicals, like aromatics, butadiene and styrene. The end process of the PTA unit (PU) dominates GHG emissions, reaching 365.6 kg CO2 eq·t−1, accounting for 22.3%, driven by extra xylene input, various catalyst consumption, auxiliary chemicals, and energy intensity. After allocating steam-related emissions from coal-fired power stations, the GHG emissions of the PU rise to 400.9 kg CO2 eq·t−1. Sensitivity analysis demonstrates that replacing conventional hydrogen with green hydrogen slashes hydrogen-related global warming potential (GWP) contribution by 61.5%. In addition, a 10% increase in electricity, coal, or steam elevates system GWP by 0.80%, 0.036% and 2.48%, respectively. The findings demonstrate that energy structure optimization and green hydrogen integration represent decisive levers for PTA decarbonization, providing data-driven insights for industrial transition under a carbon reduction policy framework.

Clean Technologies doi: 10.3390/cleantechnol8030077

Authors: Prashant Sharan Lucky E. Yerimah Manvendra Dubey Harshul Thakkar Mohamed Mehana Troy Semelsberger Michael Heidlage Rajinder Singh

Given the large natural gas (NG) reserves of the Intermountain West (I-WEST) region in the USA, it can emerge as a leader in hydrogen (H2) production. Currently, H2 production via steam methane reforming (SMR) of NG releases carbon dioxide (CO2) and the natural gas infrastructure has fugitive NG and H2 losses during production, conversion and transportation. Integrated carbon capture and sequestration (CCS) is a promising approach for producing hydrogen and CO2 from the SMR process for industrial uses including power, chemicals and fuels. However, the NG losses and regional water availability can be limiting factors for H2 production. H2 production assessments are often made at the global scale and neglect regional factors such as abundant gas and limited water in the I-WEST. We demonstrate that a regional SMR process unit sitting near NG wells offers opportunities to significantly reduce fugitive NG losses. We show that regional H2 production by SMR has a lower emissions profile than widespread natural gas combustion in the I-WEST and reduces the H2 production cost as well. Replacing the I-WEST transportation sector with H2 fuel cell vehicles and using 100% H2-powered electricity can provide substantial reductions in water consumption and fuel costs. This is better than blending H2 with NG which is more expensive. The captured CO2 can be effectively used for enhanced oil recovery in I-WEST. Finally, the potential of utilizing produced, brackish and treated impaired water sources is assessed to meet the water needs for H2 production in the I-WEST.

Clean Technologies doi: 10.3390/cleantechnol8030076

Authors: Ojo Olufisayo Riaan Stopforth

This study presents an experimental engine map investigation of waste swine oil biodiesel (WSO B100) in a single-cylinder, four-stroke variable compression ratio compression ignition engine, quantifying the coupled effects of compression ratio and load on brake thermal efficiency, brake-specific fuel consumption, torque, brake power, and regulated emissions of NOx, CO, HC, and CO2. Compression ratios of 12, 14, 16, and 18 were evaluated at dynamometer loads of 25%, 50%, and 75% under steady-state operation. The study’s primary contribution is a structured compression ratio–load mapping framework that produces consistent performance emission response surfaces and, supported by statistical modeling and sensitivity analysis, resolves main and interaction effects to identify operating regions that balance efficiency and emissions. Methodological traceability is strengthened by attaching fuel energy and mass flow calculations to batch-specific fuel properties, including viscosity and density, and by using calorimetry-derived heating value in efficiency calculations. Increasing the compression ratio from 12 to 18 improved brake thermal efficiency by 3–10% at low load and reduced brake-specific fuel consumption, while NOx increased by 20–30% across the load range. Increasing load raised brake thermal efficiency from 29% at 25% load to 42% at 75% load and reduced brake-specific fuel consumption from 309 to 215 g/kWh; NOx peaked at 488 ppm at 75% load and compression ratio 18. CO and HC decreased with both load and compression ratio, reaching minima of 0.15% and 30 ppm, whereas CO2 increased primarily with load. Relative to diesel, WSO biodiesel showed 8–12% higher brake-specific fuel consumption and 2–4% lower peak brake thermal efficiency, but achieved substantial CO and HC reductions. Generally, WSO biodiesel operates effectively across a wide compression ratio range with broadly comparable performance to diesel. However, increased NOx and reduced low-load efficiency indicate the need for targeted calibration or emission control.

Clean Technologies doi: 10.3390/cleantechnol8030075

Authors: Zhigang Shi Shiwei Xia Peng He Lin Zhang Nuochen Wang Yu Wang

Compared with previous analytical models that mostly neglect air–lining coupled heat transfer, the proposed model innovatively introduces this mechanism and achieves a maximum error reduction of 0.5% against experimental data. The analytical solution of the model is obtained by using the Green’s function method. The reliability and accuracy of this model are confirmed through comparisons with existing experimental data. Research indicates that adjusting the tunnel air temperature improves the ground heat exchanger’s heat exchange efficiency more significantly than modifying the thermal conductivity of the lining. In the tested range, as the flow velocity increases, its influence on the heat transfer effect gradually weakens. The simulation results indicate that under summer operating conditions, only approximately 5–8% of the heat transferred by the ground heat exchanger is dissipated to the tunnel air-side environment, while the vast majority (92–95%) is conducted to the surrounding rock.

Clean Technologies doi: 10.3390/cleantechnol8030074

Authors: Irfan Basturk Ibrahim Ozdemir Hande Gulcan Selda Murat Hocaoglu Recep Partal Burak Bozcelik Charuka Meegoda Harsha Ratnaweera Zakhar Maletskyi

Accurate and rapid determination of moisture content in waste sludge is essential for optimizing dewatering processes, reducing disposal costs, and minimizing environmental impact. This study investigates the use of Fourier Transform Near-Infrared (FT-NIR) spectroscopy combined with Partial Least Squares Regression (PLS-R) for predicting the moisture content of dewatered sludge. A total of 96 sludge samples, with dry matter contents ranging from 12.4% to 24.6%, were collected from two treatment plants. FT-NIR spectra were acquired over the 800–2500 nm range, and chemometric models were developed to correlate spectral information with gravimetrically determined moisture content. The optimized PLS-R model demonstrated strong predictive performance, achieving a cross-validated coefficient of determination (R2CV) of 0.87, a root mean square error of cross-validation (RMSECV) of 0.92%, and a residual predictive deviation (RPD) of 2.73. Independent test set validation confirmed the robustness of the model (R2Test = 0.88, RMSEP = 0.88%, RPD = 2.92), supported by strong calibration results (R2CT = 0.95, RMSEE = 0.60%, RPD = 4.46). Principal component analysis indicated that spectral variability observed in sludge samples was primarily associated with wastewater treatment plant (WWTP)-specific characteristics, reflecting moisture–organic matter interactions. These results demonstrate that FT-NIR spectroscopy is a promising tool for sludge moisture prediction.

Clean Technologies doi: 10.3390/cleantechnol8030073

Authors: Igor Kogut Juliane Alberts Bianca-Michaela Wölfling Stephan Hussy Daniel Polak Maciej Szwast

Domestic wastewater is a chemically complex and highly variable mixture of pollutants generated by everyday household activities, yet its contribution to environmental contamination is still frequently underestimated and only 56% of wastewater worldwide is being treated. This review provides a structured and quantitative assessment of major domestic wastewater pollutant groups, their principal exposure pathways, and current and emerging treatment technologies. Beyond a conventional narrative synthesis, the review derives per capita annual emission estimates from published data and uses these to compare pollutant groups by mass flow and environmental relevance. The analysis shows that high-volume household inputs, particularly sodium chloride from domestic water softening, toilet paper, personal-care products, detergents, and cleaning agents, can contribute substantially to overall pollutant loads, whereas lower-mass contaminants such as pharmaceuticals, antibiotics, PFAS, heavy metals, and microplastics remain critical because of their persistence, biological activity, and incomplete removal during treatment. The review further highlights that conventional wastewater treatment systems are often poorly equipped to remove many of these emerging contaminants effectively, especially under decentralised or only partially advanced treatment conditions. Advanced and hybrid technologies, including membrane bioreactors, nanofiltration, reverse osmosis, adsorption, photocatalysis, and electrochemical processes, offer clear potential, but their broader implementation remains constrained by cost, energy demand, fouling, and concentrate management. Overall, the added value of this review lies in linking mass-based pollutant prioritisation with treatment performance, thereby providing a more systematic basis for identifying dominant household emission pathways and for guiding targeted mitigation and technology selection in future wastewater management.

Clean Technologies doi: 10.3390/cleantechnol8030071

Authors: Milena Senjak Pejić Mladenka Novaković Bežanović Mirna Radović Igor Peško Maja Petrović

The construction sector is a major consumer of raw materials and a significant source of greenhouse gas emissions, necessitating data-driven approaches to support circular economy implementation and sustainable project management. This study develops an integrated framework combining machine learning-based material stock prediction, carbon footprint assessment, and Environmental, Social, and Governance (ESG) performance evaluation for construction projects. A dataset of 128 residential buildings was compiled from official use-permit documentation. After dimensionality reduction using variance filtering and Spearman correlation analysis, 25 regression algorithms were evaluated to estimate quantities of concrete, reinforcement, and brick products. The K-Nearest Neighbor (KNN) Regressor achieved the best predictive performance, with mean absolute percentage errors of 10.64% for concrete, 10.23% for reinforcement, and 16.05% for brick products. Predicted material quantities were used to calculate CO2 emissions across materialization, demolition, and disposal phases under linear and circular scenarios. The results indicate that circular economy implementation significantly reduces total emissions, particularly for concrete, with reductions of up to 97% under idealized full-substitution conditions, representing an upper-bound estimate. ESG assessment using the Delphi method identified environmental indicators as the most significant sustainability dimension. The proposed framework enables early-stage emission estimation and supports informed decision-making toward low-carbon and resource-efficient construction practices.

Clean Technologies doi: 10.3390/cleantechnol8030072

Authors: Heloísa Schneider Rolando Chamy César Valderrama Andrés Morales Fernanda Farías Sergi Vinardell

Chile is widely regarded as a key global player in green hydrogen production due to its exceptional renewable energy potential, which enables low-carbon and competitive production costs. This article provides a comprehensive review of Chile’s green hydrogen sector, evaluating the transition from early strategic goals to the current phase of industrial scaling. It offers an integrated analysis of the regulatory framework, infrastructure deployment, and the techno-economic variables essential for integrating Chilean derivatives into global markets. The country has established a supportive framework through its National Green Hydrogen Strategy (NGHS), which sets out goals of 25 GW of installed electrolyzer capacity and USD 2.5 billion in annual exports by 2030. Despite these ambitious targets, actual deployment remains in the early stages, with only 3.9 GW currently in the implementation phase and a lack of fully operational industrial-scale facilities. Furthermore, initial NGHS projections suggested a levelized cost of hydrogen (LCOH) of USD 1.3–1.4/kg by 2030. However, current calculations point to a more complex reality of approximately USD 3.1/kg due to infrastructure bottlenecks and global supply chain pressures. While Chile’s renewable resources ensure low production-stage emissions, the absence of explicit regulatory carbon targets underscores the need for comprehensive life-cycle assessments encompassing manufacturing and global distribution. Overall, this review concludes that Chile should overcome persistent regulatory and logistical constraints to consolidate a robust and internationally competitive green hydrogen sector, aligned with its 2050 carbon neutrality objectives.

Clean Technologies doi: 10.3390/cleantechnol8030070

Authors: Junnan Li Jingxin Zhang Chen Yu Shiqi Hou Peng Li Kaifeng Yu Xu Guo Fei Dou Xinglin Zhang Yiliang He

Rapid global urbanization is driving a surge in solid waste generation, while conventional treatment systems face both environmental risks and operational uncertainty. Digital twins, which enable real-time mapping between physical assets and virtual spaces, offer a computable and verifiable route toward low-carbon, resource-efficient, and intelligent waste management when deeply integrated with the Internet of Things, big data, and artificial intelligence. This study develops a comprehensive review tracing the digital twins from static geometric mirroring to dynamic, cognitive co-symbiosis, and summarizes a multidimensional architecture spanning physical, virtual, data, service, and connectivity layers, together with coupling mechanisms involving IoT sensing, federated learning, multimodal big data, and large model agents. The study aims to provide a theoretical framework and methodological references for advancing digital twin-enabled solid waste valorization. Building on this framework, we examine recent progress in three representative application scenarios for solid waste treatment, and identify key technical bottlenecks, including heterogeneous data fusion, model generalization across facilities and contexts, and real-time computation under constrained resources. We highlight the need for standardization, uncertainty quantification, cybersecurity, and lifecycle evaluation to support reliable prediction, optimization, and decision-making in real operations. Finally, we discuss future directions such as edge intelligence and the integration of city-scale material and energy networks.

Clean Technologies doi: 10.3390/cleantechnol8030069

Authors: Juan Carlos Sainz-Hernández Prabhaharan Renganathan Edgar Omar Rueda Puente

Eggshell waste generated by the poultry processing industry represents a significant yet underutilized biogenic resource with substantial potential for sustainable agricultural and environmental applications. Globally, several million metric tons of eggshell residues are produced annually, consisting predominantly of calcium carbonate (CaCO3) in the form of calcite, along with minor quantities of organic matrices and trace minerals. These physicochemical characteristics make eggshells a promising renewable alternative to conventional mineral sources for use as fertilizers, soil amendments, and biomaterials. Recent studies have shown that finely ground eggshell powder (ESP) is an effective liming material that can regulate soil chemical conditions and improve agronomic performance under acidic soil conditions. Furthermore, eggshell-derived materials have been incorporated into composting systems, biochar composites, and nanostructured fertilizers to enhance nutrient dynamics, immobilization of contaminants, and microbial activity. Advances in nanotechnology have facilitated the synthesis of nano-calcium carbonate (NCC) and nanohydroxyapatite (nHAP) fertilizers with improved nutrient supply and controlled-release properties. However, challenges associated with nanosafety evaluation, large-scale processing technologies, regulatory harmonization, and long-term field validation remain. Therefore, this review critically synthesizes the structural, biochemical, and physicochemical properties of eggshells and eggshell membranes, examines their applications in sustainable agriculture and environmental remediation, and identifies the key research priorities required to advance eggshell valorization within circular bioeconomy strategies.

Clean Technologies doi: 10.3390/cleantechnol8030068

Authors: Maria Avrami Christina Lazaratou Zacharias Frontistis Athanasia Tekerlekopoulou Vasilios Georgakilas Dimitris Vayenas

Propyl-paraben (PrP) is a common preservative found in cosmetics and pharmaceutical products. It is classified as a category 1 endocrine-disrupting compound, which highlights the importance of efficiently removing it from water during treatment processes. This study investigates the potential of using Leptolyngbya sp. dominated cyanobacterial biomass residues, in both their raw and hydrothermally treated (hydrochar) forms, for the removal of PrP from aqueous media. Batch and fixed-bed column experiments were carried out under varying conditions to assess adsorption kinetics and equilibrium behavior. Both raw biomass and hydrochar exhibited satisfactory PrP removal, achieving maximum adsorption capacities of 224.58 and 258.55 mg/g respectively, at 10 mg/L initial PrP concentration and 23.33 mg/L adsorbent dosage. Equilibrium data were best described by the Freundlich isotherm model, indicating a heterogeneous surface and multilayer adsorption. The kinetic analysis revealed that the adsorption behavior, for both adsorbents, was best described by the pseudo-second-order model, while the thermodynamic evaluation revealed negative ΔH° and ΔS° values, confirming an exothermic, physisorption-driven process. The adsorption mechanism was further investigated through surface characterization techniques, including Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, N2 physisorption, and zeta potential analysis. The findings demonstrate the potential of microalgal biomass as a low-cost, sustainable biosorbent, for emerging contaminants, reinforcing its role in advanced water treatment and circular economy strategies.

Clean Technologies doi: 10.3390/cleantechnol8030067

Authors: Cristina-Gabriela Grigoraș Andrei-Ionuț Simion Lidia Favier

Emerging compounds in water, ranging from dyes to pharmaceuticals, negatively impact living organisms and challenge the industries responsible for their release. These pollutants exhibit chemical persistence and resistance to conventional treatment processes. Adsorption is considered an effective and accessible approach, particularly when low-cost and renewable materials are employed. The Problem-Intervention-Comparison-Outcome (PICO) framework and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines were followed. A structured search of Scopus was conducted to identify English-language original peer-reviewed articles published between 2016 and 2025 addressing the use of fruit waste (FW)-derived adsorbents for water decontamination. After independent screening, 528 studies were included. Risk of bias was assessed qualitatively. Due to substantial heterogeneity in materials, contaminants, and experimental designs, findings were synthesized narratively. FW-derived adsorbents were evaluated in terms of synthesis routes, physicochemical characteristics, adsorption mechanisms, kinetic and equilibrium behavior, process optimization and regeneration performance. Correlations were observed between surface functionalization, material properties and contaminant-specific removal efficiency, while limitations were noted for multi-component systems, regeneration stability, standardization and scale-up. By integrating material design with process-level considerations, this review outlines priorities for advancing FW valorization toward practical and sustainable water treatment applications.

Clean Technologies doi: 10.3390/cleantechnol8030066

Authors: Luigi Madeo Pietro Figliuzzi Assunta Perri Anastasia Macario Carlo Siciliano Pierantonio De Luca

This study investigates the use of type A zeolite as a filtering material for the removal of toxic and carcinogenic compounds from cigarette smoke, which contains nicotine and other harmful substances produced by tobacco combustion. The aim is to evaluate the effectiveness of zeolite in reducing exposure to secondhand smoke, with particular attention to health and environmental impacts. The zeolite was characterized using SEM-EDS, XRD, DSC, and TGA to determine its morphology, chemical composition, crystalline structure, and thermal stability. An experimental setup was designed to simulate realistic smoking conditions and test filter efficiency based on the active mass. The system allowed identification of harmful substances trapped in the filter and those remaining in the air. Performance was assessed through gravimetric analysis and GC-MS, enabling identification of adsorbed and non-adsorbed compounds. Results demonstrate significant efficiency in selective removal of toxic components. Finally, filter performance was compared with carbon nanotubes, tested under the same experimental protocol.

Clean Technologies doi: 10.3390/cleantechnol8030065

Authors: Lucía Pérez-Gandarillas Berta Galán Javier R. Viguri

Maritime transport is energy-efficient but remains heavily dependent on fossil fuels. Renewable electricity-based ammonia (e-NH3) has emerged as a promising alternative, particularly through small-scale, modular production. Assessing its economic viability is essential for future adoption, and techno-economic analysis offers a structured way to evaluate its feasibility. This study investigates the cost performance of a small-scale offshore e-NH3 plant of 2.4 tons per day (tpd) at the Port of Santander, Spain, based on nitrogen obtained via membrane separation and hydrogen from electrolysis of pretreated seawater. The results are based on process simulation outcomes obtained using ASPEN v14, and the detailed cost breakdown is derived from modular costing methodologies applied to preliminary process designs and sensitivity analyses of the levelized cost of ammonia (LCOA) with respect to the main variables. A comparative review of LCOA values reported in the literature for offshore and onshore e-NH3 plants is provided. An estimated CAPEX of 5.99 M EUR (equivalent to 0.53 M EUR/y), OPEX of 1.58 M EUR/y, and an LCOA of 2408 EUR/tNH3 are obtained, with equipment investment and operating costs identified as the most influential parameters. The results highlight the need for supraregional techno-economic studies considering optimal offshore wind availability within a collaborative interregional framework.

Clean Technologies doi: 10.3390/cleantechnol8030064

Authors: Maria N. Berradre Cristina Arroqui Idoya Fernández-Pan María José Beriain Francisco C. Ibañez Paloma Vírseda

The valorization of agro-industrial by-products through sustainable extraction of bio-compounds is a key challenge within circular economy and clean-processing frameworks, as large volumes of tomato and artichoke residues are generated by the food industry. This study evaluated the impact of non-thermal technologies on the recovery of biocompounds from tomato peels and blanched artichoke bracts using single green solvents instead of solvent mixtures. Ultrasound-assisted extraction (sonication), high-pressure processing (pressurization), and dual processing (pressurization + sonication) were compared with conventional extraction. Ethanol was used for lycopene extraction, while water was employed for inulin-type fructan recovery. Lycopene, total phenolic content, antioxidant activity, and inulin-type fructans were quantified. Non-thermal treatments significantly influenced extraction yields (p < 0.05). The dual processing provided the highest lycopene and inulin-type fructan contents (1440.09 ± 0.71 µg/g DW and 5.17 ± 0.51 g/100 g DW, respectively) and enhanced antioxidant activity in tomato peels and blanched artichoke bracts (25.50 ± 0.20% and 66.11 ± 2.03%), and phenolic co-extraction (1783.2 ± 215.3 μg GAE/g DW and 27.68 ± 1.29 mg GAE/g DW) outperformed individual technologies and conventional extraction. Compared with the conventional process, dual processing improved the extraction yields of lycopene (20.60 ± 0.44%) and inulin (26.40 ± 13.95%). The findings prove that non-thermal processes, particularly when combined, intensify mass transfer and enable efficient extraction using green solvents, offering a sustainable strategy for recovering bioactive compounds from tomato and artichoke by-products.

Clean Technologies doi: 10.3390/cleantechnol8030063

Authors: Xin Chen Xiaofeng Ling Zhen Xu Yuanfen Xia

The continuous increase in atmospheric CO2 concentration exacerbates global climate change, making carbon reduction an urgent global priority. Carbonic anhydrase (CA), a highly efficient biocatalyst that converts CO2 into bicarbonate, demonstrates significant potential for carbon capture and resource utilization. However, the stability and catalytic efficiency of native CA in industrial environments are limited, particularly its poor thermal tolerance under flue gas conditions and its sensitivity to impurities, hindering its direct large-scale application. This review systematically summarizes recent advances in modifying microbial CA through protein engineering (e.g., directed evolution, rational design) and immobilization techniques, which have markedly enhanced its thermal stability, adaptability, and reusability. Among these, the integration of machine learning with high-throughput experimentation has emerged as a transformative strategy for CA engineering. Furthermore, we outline CA-driven pathways for CO2 conversion into high-value chemicals and bioenergy. Finally, future prospects are discussed, including interdisciplinary integration, computational modeling coupled with experimental validation, and comprehensive life-cycle and techno-economic assessments, to facilitate the scaled application of engineered microbial CA in carbon neutrality pathways. Collectively, this review highlights the critical role of engineered CA in bridging biocatalysis with industrial carbon management, offering a viable and sustainable pathway toward carbon neutrality.

Clean Technologies doi: 10.3390/cleantechnol8030062

Authors: Hugo Martínez Ángeles Cesar Augusto Navarro Rubio José Gabriel Ríos Moreno Margarita G. Garcia-Barajas Roberto Valentín Carrillo-Serrano Mariano Garduño Aparicio Saúl Obregón-Biosca Mario Trejo Perea

The transition toward low-carbon and circular Municipal Solid Waste (MSW) systems requires integrated evaluation approaches that consider environmental performance, technological maturity, and governance capacity. This study presents a structured, systematic review of MSW disposal and treatment practices published between 2018 and 2026, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. A total of 71 studies were included and analyzed. Due to heterogeneity in methodologies, system boundaries, and reported indicators, no formal meta-analysis was conducted. Instead, the review provides a comparative and qualitative synthesis of key environmental indicators and structural determinants. Results indicate a transition from open dumping toward engineered landfills and advanced treatment technologies, including waste-to-energy and biological processes. Open dumping is consistently associated with high greenhouse gas emissions and environmental risks, while engineered systems improve containment and enable partial resource recovery. The findings highlight that environmental performance is not determined solely by technology but by the interaction between infrastructure design, operational quality, governance capacity, and economic conditions. The proposed analytical framework supports context-sensitive waste management strategies aligned with circular economy principles and climate mitigation objectives.

Clean Technologies doi: 10.3390/cleantechnol8030061

Authors: Eleni Dalaka Gabriel Vasilakis Markos Bilbilai Dimitris Karayannis Maria Sanida Ioannis Politis Panagiota Diamantopoulou Seraphim Papanikolaou Georgios Theodorou

Polyunsaturated fatty acids, particularly γ-linolenic acid, are recognized for their therapeutic and nutritional properties. Zygomycetes, such as Cunninghamellaelegans, represent a promising microbial platform for sustainable gamma-linolenic acid (GLA) production as an alternative to conventional sources. Despite this potential, the immunomodulatory activity of metabolites from C. elegans has not been previously explored. In this study, C. elegans was cultivated on hydrolysates from discarded residues of Pleurotus spp. cultures (DRPC-HL), optimized to release assimilable compounds, promoting valorization of low-value biomass within a circular bioeconomy. Dry mycelial biomass, lipid-free biomass, and intracellular lipids from these cultures, alongside previously reported C. elegans cultures grown under nitrogen-excess (N-Xs) and nitrogen-limited (N-Lim) conditions, were tested on THP-1-derived macrophages, under lipopolysaccharide (LPS)-induced inflammatory conditions. Following in vitro gastrointestinal digestion, dry biomass and lipid-free dry biomass fractions upregulated the anti-inflammatory cytokine IL10 and downregulated IL1B and TNF, particularly from N-Xs and DRPC-HL cultures. Lipids mainly enhanced IL10 expression, especially when derived from N-Xs cultures. No changes were observed in upstream regulators (TLR2, TLR4, NFKB1, RELA), suggesting a feasible post-receptor immunomodulatory action. Overall, these findings highlight the dual value of fungal bioproducts derived from agro-industrial residues, combining sustainable bioprocessing with bioactive compound generation, supporting environmentally friendly microbial platforms for industrial applications.

Clean Technologies doi: 10.3390/cleantechnol8030060

Authors: Hamza Labjouj Loubna El Joumri Najoua Labjar Ghita Amine Benabdallah Samir Elouaham Hamid Nasrellah Brahim Bihadassen Houda Labjar El Abass El Ouardi Souad El Hajjaji

With the rapid growth of the medicinal cannabis sector, there is a growing concern regarding its environmental impact and sustainability. In recent years, life cycle assessment (LCA) studies on medicinal cannabis cultivation and processing have been conducted since 2021. However, there is a lack of comprehensive LCA studies that include all stages of medicinal cannabis cultivation and processing. In this systematic review, various LCA studies conducted from 2021 to 2025 using the ISO 14040/44 methodology are reviewed and discussed in terms of their goal and scope, life cycle inventory (LCI), life cycle impact assessment (LCIA), and result interpretation. Various environmental impact indicators are considered in this review, such as greenhouse gas emissions, energy demand, water usage, eutrophication, acidification, and resource depletion. All of these impact indicators point to a significant environmental impact of indoor cultivation in terms of greenhouse gas emissions, which vary from 2.3 × 103 to 5.2 × 103 kg CO2 eq kg−1 of dried cannabis product. Nevertheless, it is important to note that this is significantly influenced by regional electricity sources. Low-carbon-based electricity sources, especially hydro-based sources, can reduce emissions to a significant level. Cultivation outdoors presents significantly lower emissions of (60–110 kg CO2 eq kg−1), but fertilizers and substrates used in cultivation contribute significantly to emissions. Also, outdoor plants use 22.7 L plant−1 d−1 water at peak growth, while indoor plants use 9–11 L plant−1 d−1 water. Improvements in the life cycle of cannabis cultivation can be achieved through renewable energy use, water and fertilizers, substrate use and reuse, and inventories for post-harvesting activities like drying and extraction. Botanical parameters including genotype, planting density, and harvesting frequency are identified as significant but under-characterized determinants of LCA outcomes. Ethical and legal barriers are shown to be structural drivers of the LCA data gap. A SWOT analysis contextualizes the opportunities and constraints of the sector. Future research should focus on cradle-to-grave LCA and incorporate socio-economic factors for sustainability in the medicinal cannabis sector.

Clean Technologies doi: 10.3390/cleantechnol8020059

Authors: Ann-Christine Johansson Rebecka Nordsvahn André Selander Torun Hammar Jesper Eman Magdalena Juntikka

Sustainable structural composites can significantly lower vehicle-related emissions. To evaluate the recycling of different composite materials, laboratory-scale pyrolysis was conducted and assessed both technically and environmentally. Two demonstrators were studied: a truck side skirt made from natural flax and hemp fibres with polypropylene (PP), and a car front header composed of glass fibres and PP. Additional materials examined included thermoplastic composites containing polyamide 6 (PA6), bio-based polyamide 11 (PA11) and thermoset polyester. Results showed that material type strongly influenced the pyrolysis outcome, product composition and recycling potential. Glass fibres could be recovered and reused as reinforced fibres, while natural fibres could be recovered as biooil for potential use in biofuel production. Polymers were recovered as pyrolysis products that, depending on their composition, can be used in different applications, from recovering monomers from PA6 to producing hydrocarbons that may replace naphtha (from PP) or aromatics (from polyester) in the petrochemical industry. Life cycle assessment (LCA) findings revealed that the climate impact of composite recycling is primarily driven by the environmental burdens of the recycling process itself and by the ability of recovered materials and chemicals to substitute conventional fossil-based alternatives. Efficient recycling pathways are therefore essential to maximising environmental benefits.

Clean Technologies doi: 10.3390/cleantechnol8020058

Authors: Mariana Murrieta-Melchor Stephany Isabel Vallarta-Serrano Edgar Santoyo-Castelazo Sergio Alberto Navarro-Tuch

As the world faces the challenge of mitigating climate change, energy- and emissions-intensive industrial processes must be addressed urgently worldwide. The cement production industry accounts for over 8% of global greenhouse gas (GHG) emissions from calcination and fuel use. Mexico, a middle-income economy, has rising cement demand for infrastructure and commercial growth. Thus, this study analysed national cement production, the primary emitting manufacturing industry in the country, under a business-as-usual (BAU) and two alternative scenarios, using a top-down approach to model energy consumption and GHG emissions by 2050. These scenarios follow the projection of national cement production, estimated using socio-economic indicators, which are considered the main drivers of cement demand, reaching 97.3 Mt. A qualitative analysis evaluates the strengths, weaknesses, opportunities, and threats (SWOT) of implementing emission-reduction strategies. The analysis showed that the BAU scenario might reach 66.5 Mt CO2e by 2050, while the most ambitious scenario reduced direct emissions by 80.1% through carbon capture, clinker-to-cement reduction, thermal energy intensity reduction, and the use of municipal solid waste as an alternative fuel. However, incorporating these strategies in Mexico requires a more active role and investment support from key stakeholders.

Clean Technologies doi: 10.3390/cleantechnol8020056

Authors: Manuel Hernández-Escaño Rafael Borja José Carlos García-Gómez Francisco Raposo

The accumulation of dead leaves from the Mediterranean seagrass Posidonia oceanica on beaches is a natural process that results in the formation of banquettes and, in some areas, spherical debris known as aegagropiles. These structures provide essential ecosystem functions, particularly coastal protection against erosion. Despite their ecological importance, accumulated Posidonia oceanica biomass is often perceived as undesirable waste by stakeholders such as beach managers, local authorities, and tourists, leading to its systematic removal. This review summarises the chemical characteristics of this marine biomass and assesses its environmental and socioeconomic impact. Additionally, some different valorisation pathways for this biomass waste are examined, including animal feeding, bioactive compound extraction, development of biochar, biofertilisers, and compost, production of biosorbents, biocomposites and building materials, and also energy generation. The findings highlight the significant potential of P. oceanica residues within circular economy strategies and underscore the need for improved management practices that recognise their ecological value.

Clean Technologies doi: 10.3390/cleantechnol8020057

Authors: Ahmed Mohammed Inuwa Victor Oluwafemi Fatokun Emmanuel Kweinor Tetteh Sudesh Rathilal Usman Mohammed Aliyu

The sustainable valorization of food waste is essential for advancing the circular bioeconomy and reducing the environmental impacts of organic waste disposal. This study presents an integrated approach combining hydrothermal carbonization (HTC) and anaerobic digestion (AD) to recover renewable energy and valuable resources from food waste. The process was simulated in Aspen Plus® version 14.1 using thermochemical and biochemical reaction models to evaluate the effects of feed moisture (60–85%) and HTC temperature (180–280 °C) on performance. Integration of HTC and AD increased overall energy recovery by 26–38% compared to standalone AD, with a feed moisture of 85%, organic loading of 4 kg VS m−3 d−1, and mesophilic/thermophilic temperatures of 35 and 55 °C. Improvements resulted from higher methane yield (0.42 m3 CH4 kg−1 VS) from HTC liquor and energy-rich hydrochar (25–29 MJ kg−1). The techno-economic assessment indicated a net energy ratio of 2.3, an Internal Rate of Return (IRR) of 18.6%, and a 4.8-year payback period, confirming economic viability. Sensitivity analysis highlighted energy prices and feedstock costs as key drivers, while Monte Carlo simulation demonstrated stability under ±20% uncertainty. Optimal conditions (HTC at 220 °C, 65% moisture, and 100 kg h−1 solid loading) significantly enhanced profitability and carbon efficiency. Overall, the integrated HTC–AD process offers a technically, economically, and environmentally sustainable route for converting food waste into renewable energy and biochar, supporting circular bioeconomy and net-zero energy goals.

Clean Technologies doi: 10.3390/cleantechnol8020055

Authors: Haibo Liu Kai Chen Yali Zhao Weiwei Xu Qiang Li

Air flotation is widely used in wastewater treatment for the removal of emulsified oils and suspended solids. The complex flow disturbances generated during the flotation process play a critical role in determining separation efficiency. This study employs the volume-of-fluid (VOF) method within the OpenFOAM framework to simulate the aggregation and rising behavior of microbubbles (40–100 μm) and oil droplets under various perturbation conditions. The effects of different airflow disturbance patterns on the flotation dynamics of oil–gas compounds are systematically investigated. Results show that negative pulsation promotes the rising of bubble–oil aggregates, whereas positive pulsation hinders their coalescence and upward motion. Furthermore, recirculation vortices induced by surface disturbances increase the residence time of oil–gas compounds in the water column, thereby affecting overall separation performance. The findings demonstrate that introducing vertical upward flow and bilateral oblique upward airflow can enhance flotation efficiency. This work provides insights into optimizing airflow configurations for improved oil removal in wastewater treatment applications.

Clean Technologies doi: 10.3390/cleantechnol8020054

Authors: Kazhi Hawrami Bassel Eissa Abdulrahman Shahin Elvin Hajiyev Hossein Emadi Marshall Watson

Freshwater demand for cementing operations in the Delaware Basin continues to increase with expanding unconventional development, creating a high demand for an alternative source of water. This study develops a chemistry screening and operational framework to evaluate the reusability potential in cementing operations in the Delaware Basin. A three-tier screening system for the produced-water samples was established by using the major-ion chemistry, total dissolved solids (TDS), pH, and saturation index (SI) thresholds derived from the cement literature and American Petroleum Institute (API) guidelines. The results of the geochemical screening aid in classifying the water samples into four suitability categories: Excellent/Preferred, Good/Suitable, Moderate/Marginal, and Poor/Unsuitable. The results suggest that the samples obtained from the Loving, Pecos, Reeves, Eddy and Lea counties meet the criteria for reuse in cementing operations with minimal conditioning. To assess the feasibility of operational use, a probabilistic forecasting model was developed to predict the cement water demand in 2026 for the basin. Linear regression of historical drilling trends between 2015 and 2025 showcased that approximately 3595 new wells will be drilled, with an average well depth of 21,778 ft. To evaluate whether the produced-water volumes in the basin are adequate for reuse in cementing, a Monte Carlo simulation (10,000 iterations) estimated an annual cementing water requirement centered at 6.16 MMbbl/year (P50). Produced-water availability from wells classified as Excellent/Preferred was also modeled probabilistically, using uncertainty in the water–oil ratio (WOR), estimated ultimate recovery (EUR), and forecast duration. These results demonstrate the potential for produced-water reuse to reduce freshwater demand for cementing operations in the Delaware Basin.

Clean Technologies doi: 10.3390/cleantechnol8020053

Authors: Raúl Bahamonde Soria Jefferson Estupiñan Irma Gonza Monserrat Naranjo Billy D. Chinchin-Piñan Lucia E. Manangón Katherine Vaca Martha Romero-Bastidas Henry Pupiales Verónica Taco Patricia Luis

Improving the absorption of visible light in photocatalysts could enhance photocatalytic reactions and reduce energy consumption, particularly in sunny regions like Ecuador. This study reports the synthesis of ZnO and ZnO nanoparticles doped with 1.5 at.% Er, 5 at.% Al, and 1.5 at.% Er, 5 at.% Al using the sol–gel method. The effect of doping on the structure, morphology, absorption spectra, and photocatalytic properties was analyzed by XRD, SEM, EDS, and UV-Vis spectrophotometry. XRD confirmed the presence of the wurtzite ZnO structure, and UV-Vis diffuse reflection spectra showed a red shift in the band gap for doped ZnO compared to pristine ZnO. Photocatalytic activity was evaluated through the degradation of methyl orange (MO) under artificial visible light and natural sunlight in Quito, Ecuador. ZnO doped with Er/Al nanoparticles exhibited significantly enhanced photocatalytic performance under solar light, suggesting the potential for replacing artificial light and reducing operating costs in photocatalytic processes. Moreover, all doped samples retained the antibacterial properties of ZnO against B. subtilis, and Er/Al co-doping improved the inhibition of E. coli compared to undoped ZnO.

Clean Technologies doi: 10.3390/cleantechnol8020052

Authors: Héctor Rivera Diana Pinto Heidis Cano

This article presents a systematic literature review on methane (CH4) emissions from municipal solid waste (MSW) disposal sites and their implications for footprint outcomes. This review followed a PRISMA 2020 screening logic using Scopus and ScienceDirect (2019–2024); English and Spanish; subject areas: engineering and environmental, earth sciences), yielding a final sample of 30 studies for qualitative synthesis. This review focuses on how landfill CH4 is quantified and how system boundaries and functional units shape reported CO2 results. Evidence indicates that reported CH4 estimates are sensitive to methodological choices and key assumptions and site-context drivers (degradable organic carbon (DOC)/model first-order decay (FOD) and constant k, the methane correction factor (MCF), gas collection, oxidation, waste composition, landfill age/type, and climate), limiting direct comparability between studies. Mitigation and waste-to-energy pathways (capture/utilization, anaerobic digestion, and incineration) are summarized in terms of the reported climate benefits. Finally, reporting gaps are identified, and the minimum information set is outlined to improve the reproducibility of landfill-related carbon footprint estimates for planning and future research.

Clean Technologies doi: 10.3390/cleantechnol8020051

Authors: Megan Rand Wheeler Brandi Everett Victor Prybutok

Artificial intelligence presents a critical paradox for clean technology: while enabling unprecedented environmental optimization, AI deployment demands massive resource inputs that threaten to offset benefits. As global AI infrastructure investment approaches $500 billion annually, data center electricity consumption is projected to exceed 1000 TWh by 2030. We conducted a systematic literature review of 73 peer-reviewed empirical studies (2021–2025) to develop an Environmental Asset-Cost Framework categorizing AI’s impacts across five asset categories (energy optimization, production enhancement, green innovation, resource conservation, precision applications) and five cost categories (energy consumption, water use, e-waste, infrastructure, supply chain extraction). Our analysis reveals three critical insights: First, AI’s environmental impact follows a synthesized S-curve heuristic—a pattern derived from convergent but methodologically diverse evidence strands—characterized by initial emission reductions (0–2 years), mid-term rebound effects (2–5 years), and conditionally projected long-term optimization (5+ years). Second, geographical context creates 10–60× variation in outcomes; regions with high renewable electricity and water abundance achieve net benefits within 2–3 years, while fossil fuel-heavy, water-stressed regions may never reach net positive outcomes. Third, the rebound effect is predictable and manageable through strategic interventions. Our framework provides actionable deployment guidance, demonstrating that achieving AI’s net environmental benefits requires renewable energy infrastructure development before AI deployment, alternative cooling technologies, and policy frameworks incorporating temporal dynamics.

Clean Technologies doi: 10.3390/cleantechnol8020050

Authors: Hamad Ahmed Al-Ali Koji Tokimatsu

Sustainable hydrogen production in water-scarce regions poses critical environmental challenges due to limited freshwater availability and the energy intensity of seawater treatment. This study examines the environmental trade-offs of providing water for hydrogen production via seawater desalination (with or without brine treatment) or freshwater purification, using a comprehensive life cycle assessment (LCA) framework. The assessment centers on three water-stressed countries: the United Arab Emirates (UAE), Spain, and Australia. Results reveal clear trade-offs between freshwater conservation and marine environmental pressures. Brine treatment reduces nutrient-related marine impacts but increases energy-related burdens, particularly under fossil-dominated electricity systems. Water sourcing for electrolysis coupled with energy-intensive desalination systems generally exhibits higher environmental pressures than alternative configurations, whereas freshwater-based supply for hydrogen production pathways shows lower burdens in several impact categories but raise concerns regarding freshwater resource use. Sensitivity analysis confirms that system performance is strongly influenced by water demand and electricity characteristics, highlighting the importance of aligning hydrogen deployment strategies with regional energy and water conditions. Overall, the findings demonstrate that water sourcing decisions play a critical role in shaping the environmental sustainability of hydrogen systems in water-stressed regions and must be evaluated through integrated water–energy planning.

Clean Technologies doi: 10.3390/cleantechnol8020049

Authors: Feyisayo O. Adepoju Vadim A. Shevyrin Elena G. Kovaleva Alicia C. Mondragón Alberto Cepeda José Manuel Miranda

Natural deep eutectic solvents (NADESs) have emerged as promising green alternatives to conventional solvents for the extraction of bioactive compounds from plant materials. In this study, eight natural deep eutectic solvents were synthesized and evaluated for their efficiency in extracting betulin from birch bark. Extraction yield was assessed using high-performance liquid chromatography with ultraviolet detection. Among the tested systems, N3 (choline chloride and urea in a 1:1 molar) and N4 (choline chloride and fructose in a 1:1 molar) were the most effective, yielding 101.26 ± 0.03 and 243.32 ± 0.26 mg betulin per gram of dry extract, respectively. Fourier transform infrared spectroscopy analysis confirmed the structural similarity of the N4 extract to pure betulin. In addition to increased extraction performance, the N4 extract demonstrated the greatest antioxidant activity (DPPH (1,1-diphenyl-2-picrylhydrazyl): 63% and ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)): 97% inhibition) and total phenolic content (12.12 mg GAE/g extract), and betulin yield was strongly correlated with total phenolic content (TPC) and antioxidant activity (FRAP (ferric ion reducing antioxidant power), DPPH, and ABTS), indicating the preservation of bioactivity. These findings underscore the potential of NADESs as sustainable solvents for the extraction of bioactive compounds from birch bark, supporting greener extraction technologies for biomass valorization and natural product processing.

Clean Technologies doi: 10.3390/cleantechnol8020048

Authors: Ahsan Mehtab Hong-Seok Mun Eddiemar B. Lagua Hae-Rang Park Jin-Gu Kang Young-Hwa Kim Md Kamrul Hasan Md Sharifuzzaman Sang-Bum Ryu Chul-Ju Yang

Cold thermal energy storage (CTES) has emerged as a critical clean-energy technology for enhancing postharvest management in rural agricultural supply chains, where losses often exceed 20–40% due to inadequate cooling infrastructure and unreliable electricity. This review synthesizes the recent literature on CTES systems, including ice-, chilled-water-, and phase-change material (PCM)-based storage, with a focus on smart-farm integration, IoT-based monitoring, predictive control, and solar photovoltaic (PV) energy coupling. Trends in village-level cold rooms, micro-dairy milk cooling, and fruit–vegetable storage are critically examined, highlighting efficiency, resilience, and scalability relative to battery-dominant and conventional refrigeration systems. Current research gaps are identified in multi-scale modeling, PCM stability, state-of-charge estimation, techno-economic optimization, and AI-based operational strategies. Addressing these gaps is essential to realizing sustainable, low-carbon, and energy-efficient rural cold chains.

Clean Technologies doi: 10.3390/cleantechnol8020047

Authors: Shunchang Yang Na Wu Pratap Pullammanappallil

This study explores a circular bioeconomy strategy for microbrewery waste by characterizing and valorizing its primary waste streams: sugar mash water (A), spent yeast with hops (B), spent yeast without hops (C), and alkaline cleaning wastewater (D). The biochemical methane potential of the acidic organic blend (E, from A-C) was assessed under mesophilic (38 °C) and thermophilic (55 °C) conditions, revealing significant substrate-specific temperature sensitivity. The highly acidic blend E (pH 4.16) was effectively neutralized to pH 7.0 using the on-site alkaline wash water (D, pH 12.03). Mesophilic anaerobic digestion of the neutralized blend achieved a high methane yield of approximately 500 mL/g VS. Furthermore, the alkaline wash water successfully served as an in situ CO2 scrubber, upgrading biogas to ~100% methane content. This integrated approach demonstrates a viable, closed-loop pathway for microbreweries to achieve simultaneous energy recovery from organic wastes and chemical-free treatment of acidic and alkaline effluents. The findings also highlight the importance of substrate-specific thermal management and provide a robust framework for microbreweries to achieve energy independence and internal CO2 neutralization–wastewater treatment.

Clean Technologies doi: 10.3390/cleantechnol8020046

Authors: Bo Shen Xiaoyan Zheng Lili Zheng Yang Yang Dao Xiao Zhanwu Sheng Yiqiang Wang Binling Ai

The initial carbon-to-nitrogen (C/N) ratio is a fundamental parameter for aerobic composting, with a generally recommended optimal range of 25:1 to 30:1. However, in practical applications, the optimal C/N ratio often deviates from the recommended value. We attribute this discrepancy to the limitations of traditional stoichiometric methods in assessing the bioavailability of carbon and nitrogen sources. This study investigated how carbon bioavailability governs composting efficiency and product quality. Laboratory-scale aerobic composting experiments were conducted using six types of raw crop straws and two physically pretreated straws, representing a biodegradability gradient. Results demonstrated that carbon bioavailability significantly modulated the composting performance. Substrates rich in labile carbon pool (LCP), such as wheat straw and extruded cassava plant residue, demonstrated superior thermogenesis, humification, and seed germination indices compared to those dominated by recalcitrant carbon pool (RCP), such as untreated cassava plant residue. Principal component analysis confirmed a strong positive correlation between LCP content and key quality indicators. Microbiological analysis revealed that carbon source variations shaped bacterial succession: Bacteroidota abundance correlated positively with LCP, driving rapid initial degradation, whereas Pseudomonadota were more abundant in RCP-rich treatments, suggesting a role in complex polymer breakdown. This study confirmed that carbon bioavailability, rather than the bulk C/N ratio alone, is a critical limiting factor. This finding logically extends to the role of nitrogen bioavailability, suggesting that a “biochemical C/N ratio”—accounting for the lability of both carbon and nitrogen—could be a more accurate predictor of aerobic composting performance.

Clean Technologies doi: 10.3390/cleantechnol8020045

Authors: Hanyi Lin Qing Tong Sheng Zhou Cuiping Liao

Developing far-offshore wind power integrated with hydrogen production represents a critical pathway for China’s energy decarbonization. However, the investment prospects of off-grid offshore wind-to-hydrogen projects remain highly uncertain due to volatile technology costs and hydrogen prices, complicating the evaluation of project value and optimal timing. To address the oversimplified treatment of electrolyzer operation and the limited consideration of alkaline electrolyzers in the existing studies, this paper proposes an integrated assessment framework that combines time-series operational simulation with real options analysis. A detailed dynamic model of an alkaline (ALK)–proton exchange membrane (PEM) hybrid configuration is developed to simulate the coordinated hydrogen production under fluctuating wind power. Technical learning effects and stochastic hydrogen price processes are incorporated, and the least-squares Monte Carlo method is applied to determine the optimal investment strategies. A case study of a planned far-offshore wind farm in Guangdong indicates that, compared with a standalone PEM configuration, the hybrid configuration reduces the levelized hydrogen cost by about 15%, increases the investment value by up to 17 times under slow technological progress, and brings forward the optimal investment year by five years, from 2039 to 2034. Sensitivity analysis shows that expected hydrogen prices and discount rates dominate the investment outcomes.

Clean Technologies doi: 10.3390/cleantechnol8020044

Authors: Andrzej Piotrowicz Janusz Kolczyński Mirosław Kostrzewa Wojciech Kaczmarek Bogdan Samojeden

Microwave-assisted depolymerization (MD) of heterogeneous postconsumer plastics was carried out in a quarter-scale reactor to evaluate product composition and the influence of feedstock type on oil quantity and quality. Various waste streams, including: PS, PP, ABS materials, keyboard housings, textile plastics, PCBs, and mixed electronic components, were processed in 3–6 kg batches using magnetron powers up to 2 × 1.55 kW. All experiments yielded a condensed liquid fraction, with color intensity correlating with aromatic content. FTIR spectroscopy showed that all oils consisted of hydrocarbon matrices dominated by aliphatic C-H stretching bands (2956–2850 cm−1). Aromatic contributions varied significantly: PS produced oils rich in aromatic OOP C-H bands (900–650 cm−1), PP yielded predominantly aliphatic oils with minor aromatic features, and ABS or electronics materials produced mixed aliphatic–aromatic profiles. Textile oils additionally exhibited carbonyl and O-H bands, indicating oxygenated decomposition products. Fractional distillation separated the oils into low-boiling aliphatic (<250 °C) and heavier aromatic (250–350 °C) fractions. These results suggest that MD reliably converts diverse plastic wastes into hydrocarbon oils whose spectroscopic characteristics reflect both feedstock composition and thermal pathways intrinsic to microwave heating.

Clean Technologies doi: 10.3390/cleantechnol8020043

Authors: Vu-Mai-Linh Nguyen Adama Ndao Jean-François Blais Kokou Adjallé

This study explores the potential of using paper pulp mill sludge (PPMS) as an economical substrate for producing high-value protease enzymes with an indigenous bacterial strain, Bacillus tropicus P4. Isolated directly from PPMS, B. tropicus P4 showed high protease-producing ability, approximately 134 U/mL after 48 h—more than three times the yield of the benchmark strain (B. megaterium). Among various additives tested to boost enzyme production, Tween 80 emerged as the most effective, increasing enzyme activity by more than threefold compared to the control. Scale-up experiments in bioreactors of 5 L and 150 L confirmed that B. tropicus P4 maintains high protease yields under typical cultivation conditions with minimal modifications, specifically the addition of Tween 80 (1%) and increased total solids concentration (25 g/L). In the 5 L bioreactor, enzyme production peaked at approximately 755 U/mL within 24 h, while the 150 L bioreactor consistently achieved high enzyme activity (~848 U/mL). These results support the feasibility of a simple and scalable approach for converting industrial sludge into high-value protease enzymes, contributing to resource recovery and circular bioeconomy strategies.

Clean Technologies doi: 10.3390/cleantechnol8020042

Authors: Ifigeneia Nikolaidou Josep Oriol Pou Maria Auset

The environmental crisis and the growing need to reduce solid waste make it imperative to adopt integrated, scientifically sound, and environmentally friendly solid waste management practices in order to ensure a sustainable future. This study presents an alternative waste management proposal in accordance with the standards set out in the European Waste Directive (Directive 2018/850/EC) in order to lessen greenhouse gas emissions. The primary objective is to develop a circular waste management system that uses waste as feedstock for the production of biofuel in order to meet Catalonia’s energy needs and, at the same time, reduce its environmental footprint. Waste that is highly biodegradable and rich in organic matter cannot be disposed of in landfills, according to order TED/834/2023, and is therefore used to produce biogas through anaerobic digestion (AD) or to produce compost. In addition, gas emissions from landfills, which are rich in methane, are also collected and used for biogas production. Plans for biogas production at landfills and at an anaerobic digestion biogas plant, and for compost production from organic waste, were implemented using SuperPro Designer simulation software. The research has shown that this approach to solid waste management offers positive results in terms of energy due to biogas production, in terms of the environment due to waste reduction and compost production, and in terms of the economy due to a 25% increase in the efficiency of the biogas plant.

Clean Technologies doi: 10.3390/cleantechnol8020041

Authors: Hyung-kyu Lee Go-eun Kim Seong-ho Jang Ho-min Kim Byung-gil Jung Young-chae Song Won-ki Lee

Soluble cutting fluids (SCFs) from metalworking processes pose significant treatment challenges. Here, SCFs were treated using a monopolar electrochemical (EC) system, using turning scrap generated from metalworking operations as the anode. The system was operated for 60 min under various conditions, including different anode materials, electrolyte addition, aeration, and initial pH. Treatment performance was evaluated in terms of chemical oxygen demand (CODCr) and total organic carbon (TOC) removal efficiencies and specific energy consumption (SEC) for CODCr removal. The Al scrap (20 g/L) showed the optimal overall performance, achieving CODCr and TOC removal efficiencies of 29.28% and 25.62%, respectively, with an SEC comparable to that of the Al electrode. Electrolyte addition improved the energy efficiency under all conditions, with NaNO3 10 mM yielding the lowest SEC (0.57 kWh/kg-CODCr), and aeration negatively affected both removal efficiency and energy consumption. Although acidic conditions (pH 2) resulted in high apparent removal, most of the reduction occurred during pre-treatment pH adjustment, and the highest energy efficiency was achieved at pH 7 (0.47 kWh/kg-CODCr). These results demonstrate that Al turning scrap is a promising alternative anode material for electrochemical treatment of SCFs with optimized electrolyte addition and operating pH enabling improved energy efficiency.

Clean Technologies doi: 10.3390/cleantechnol8020040

Authors: José Cabrera-Escobar Carlos Mauricio Carrillo Rosero César Hernán Arroba Arroba Santiago Paúl Cabrera Anda Catherine Cabrera-Escobar Raúl Cabrera-Escobar

This study presents a two-dimensional computational fluid dynamics analysis of a vertical-axis Savonius-type wind turbine under atmospheric conditions representative of an educational environment located in the Ecuadorian Andean region. Unlike previous studies conducted under sea-level meteorological conditions, this research is performed under high-altitude conditions (2723 m a.s.l.). The unsteady flow around the rotor was simulated using a two-dimensional approach based on the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations, discretized with the finite volume method and coupled with the k–ω Shear Stress Transport (SST) turbulence model. The rotor rotation was modeled using sliding mesh technique, employing a second-order implicit time scheme to ensure numerical stability and adequate temporal resolution. The numerical model was configured for a tip speed ratio of 0.8 and a wind speed of 3.9 m/s. The time step was defined based on a constant angular advancement of the rotor per time iteration, ensuring numerical stability and adequate temporal resolution. The aerodynamic torque was obtained by integrating the pressure and viscous forces acting on the blades, allowing the calculation of the mechanical power generated and the power coefficient. The results showed a periodic and stable torque behavior after the initial transient cycles, yielding an average torque of 0.7687 N·m and a mechanical power of 5.17 W, while the power coefficient reached a value of 0.2102. Analysis of the flow fields revealed the formation of a low-velocity wake downstream of the rotor, regions of high turbulent kinetic energy associated with periodic vortex shedding, and a significant pressure difference between the advancing and returning blades, confirming that turbine operation is dominated by drag forces. The numerical results were validated through comparison with previous studies, showing good agreement and demonstrating the reliability of the proposed Computational Fluid Dynamics (CFD) approach. This study highlights the potential of Savonius turbines for low-power applications in urban and educational environments, as well as the usefulness of CFD as a tool for evaluating and optimizing their aerodynamic performance.

Clean Technologies doi: 10.3390/cleantechnol8020039

Authors: Kamyar Shirvanimoghaddam Agnieszka Krzyszczak-Turczyn Ilona Sadok Bożena Czech Omid Zabihi Minoo Naebe

The global demand for high-quality food is rising due to the increasing population, necessitating intensive farming practices that often involve the extensive use of pesticides, which can accumulate in soils and enter the food chain. This study explores the use of synthesized and commercial graphenes for the removal of kresoxim-methyl (KM), a common strobilurin fungicide, from soil. Adding only 1 wt% of graphene to soil enhanced its partitioning capacity from about 4.77 mg/g for unamended soil to 9.57 mg/g, indicating effective immobilization and reduced environmental risk. The adsorption efficacy was notably higher in materials rich in oxygen-containing functional groups and with a large surface area, highlighting the significance of surface characteristics and porosity. The adsorption followed pseudo-second-order kinetics, underscoring the importance of surface heterogeneity in KM adsorption.

Clean Technologies doi: 10.3390/cleantechnol8020038

Authors: María-Isabel Aguilar Mercedes Lloréns Víctor-Francisco Meseguer Juan-Francisco Ortuño Ana-Belén Pérez-Marín Rafael Valentín

Adsorption is an effective method frequently used for removing contaminants, including dyes, from liquid effluents. This study uses silk fibroin nanoparticles produced by the Bombyx mori moth as an adsorbent material to remove methylene blue dye from aqueous solutions. Batch tests were carried out to examine the effect of pH and temperature on methylene blue adsorption and to obtain kinetic and equilibrium data. The experimental data were fitted to different kinetic models (pseudo-first-order, pseudo-second-order, Elovich, intraparticular diffusion and Bangham) and isotherm models (Langmuir, Freundlich, Sips and Redlich–Peterson). The experimental data can be best explained by the pseudo-second-order and Bangham kinetic models. The adsorption capacity increases with temperature so adsorption is an endothermic process. The maximum adsorption capacities achieved in the experiments were 122 mg·g−1, 132 mg·g−1, and 155 mg·g−1 at temperatures of 10 °C, 25 °C, and 40 °C, respectively. Among the models studied, the ones that best describe the equilibrium data are Freundlich and Redlich–Peterson models.

Clean Technologies doi: 10.3390/cleantechnol8020037

Authors: Jesica Vilchez Cairo Tessa Yazmin Sanchez Grandez Danai Noelia Hidalgo Cabrera Luis Fernando Medrano Canchari Julio Rodrigo Tornero Loayza Doris Esenarro Carlos Manuel Cavani Grau Miguel Ramón Cobeñas Cabrera

The natural resources and local communities of Madre de Dios, Peru, face severe environmental degradation due to illegal mining, deforestation, and the expansion of agricultural activities, threatening one of the most ecologically sensitive regions of the Amazon. This research proposes a low-carbon and bioclimatic architectural design for a Sustainable Interpretation and Research Center dedicated to the conservation of the ecosystems of Manu National Park. The study is based on an analysis of the surrounding environment in terms of flora, fauna, and climate, applying bioclimatic strategies focused on sustainability and supported by specialized digital tools (Revit 2024, Canva, Global Mapper 2024, SketchUp 2024, Photoshop 2022, and Illustrator 2022). The project presents a bioclimatic architectural design that integrates constructive techniques ensuring thermal comfort in a warm-humid climate, while promoting the use of clean technologies such as photovoltaic solar systems generating 15,571.8 kWh per year and a rainwater harvesting system collecting 70,675 L annually. The infrastructure is built with bamboo and locally sourced wood, renewable materials that ensure durability and low environmental impact. In addition, the design includes the reforestation of 17.92% of the total area and 3.46% of public spaces, incorporating native species such as Brazil nut, rosewood, and capirona to reinforce local biodiversity. Overall, this research demonstrates how low-carbon construction, renewable materials, and bioclimatic design can contribute to sustainable development, environmental awareness, and the preservation of natural ecosystems in tropical regions.

Clean Technologies doi: 10.3390/cleantechnol8020036

Authors: Ibrahim Elnaml Louay N. Mohammad Heather Dylla Moses Akentuna Samuel Cooper

The U.S. transportation section contributed a third of the national Greenhouse Gas (GHG) emissions in 2022. As such, the Louisiana Department of Transportation and Development (DOTD) initiated federally funded efforts to create Life Cycle Assessment (LCA) models for pavement systems. The objective of this study was to quantify the holistic, cradle-to-grave environmental impacts of asphalt pavements containing Reclaimed Asphalt Pavement (RAP) and Warm Mix Asphalt (WMA) technologies using a closed-loop recycling assumption based on 100% RAP recovery at the end-of-life stage, consistent with current practice in Louisiana. Five field sections in service for up to 16 years were collected from DOTD’s LaPave database. The LCA framework followed ISO 14040 and included definition of cradle-to-grave system boundaries, a functional unit based on in-service pavement sections, inventory data derived from public databases and field performance records, and use-phase modeling based on pavement–vehicle interaction. Public datasets were used to quantify GHG emissions across all life cycle phases. Results indicated WMA additives reduced production and construction GHG emissions by 5%. An RAP increase by 1% decreased material/construction GHG emissions by approximately 0.9%; however, it potentially increased use-phase emissions due to roughness. Mixtures combining WMA and RAP emitted the lowest GHG among the studied mixtures, which promotes integrating sustainable pavement strategies.