Clean Technol., Volume 8, Issue 4 (August 2026) – 31 articles

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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 $T_0$ 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 ${5 }^{\circ }$C to ${40 }^{\circ }$C. At $T_0={20 }^{\circ }$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 $T_0={37.4 }^{\circ }$C, the recuperator undergoes a priority inversion from destruction-dominated ($f_b=14.7\%$) to fully capital-dominated ($f_b=100\%$). 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 $T_0={20 }^{\circ }$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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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 (E_a). 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 E_a 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). Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article