Clean Technol., Volume 7, Issue 1 (March 2025) – 27 articles

Solar air heating systems offer an effective alternative for reducing greenhouse gas emissions at a profitable cost. This work details the design, construction, and experimental evaluation of a novel double-pass V-trough solar air heater with semicircular receivers, which was built with low-cost materials readily available in the Mexican market. Thermal performance tests were conducted in accordance with the ANSI-ASHRAE 93-2010 standard. The results indicated a peak collector efficiency of 0.4461 and total heat losses of 8.8793 W/(m² °C), with an air mass flow rate of 0.0174 kg/s. The instantaneous thermal efficiency varied between 0.2603 and 0.5633 with different air flow rates and an inlet air temperature close to the ambient temperature. The outlet air temperature reached 70 °C, making it suitable for dehydrating fruits or vegetables at competitive operating costs. Additionally, a second-law analysis was carried out, and the exergy efficiency was between 0.0037 and 0.0407. Finally, a Levelized Cost of Energy analysis was performed, and the result was USD 0.079/kWh, which was 31% lower than that of a conventional electric air heater system. Full article

Waste management is one of the key areas where circular models should be promoted, as it plays a crucial role in minimizing environmental impact and conserving resources. Effective material identification and classification are essential for optimizing recycling processes and selecting the appropriate production equipment. Proper sorting of materials enhances both the efficiency and sustainability of recycling systems. The proposed study explores the potential of using a cost-effective strategy based on hyperspectral imaging (HSI) to classify space waste products, an emerging challenge in waste management. Specifically, it investigates the use of HSI sensors operating in the near-infrared range to detect and identify materials for sorting and classification. Analyses are focused on textile and plastic materials. The results show promising potential for further research, suggesting that the HSI approach is capable of effectively identifying and classifying various categories of materials. The predicted images achieve exceptional sensitivity and specificity, ranging from 0.989 to 1.000 and 0.995 to 1.000, respectively. Using cost-effective, non-invasive HSI technology could offer a significant improvement over traditional methods of waste classification, particularly in the challenging context of space operations. The implications of this work identify how technology enables the development of circular models geared toward sustainable development hence proper classification and distinction of materials as they allow for better material recovery and end-of-life management, ultimately contributing to more efficient recycling, waste valorization, and sustainable development practices. Full article

In the context of global warming, technologies and studies aimed at mitigating carbon dioxide (CO₂) have become increasingly relevant. One such technology is CO₂ capture by activated and functionalized N-doped carbon from biomasses. This paper explores the ways to find the optimal CO₂ adsorption conditions, based on the carbonization temperature, impregnation rate, and preparation method, considering four different preparation routes in activated and functionalized carbon-N (PCs) of banana peel biomass residues. PCs were produced and chemically activated by K₂C₂O₄ and H₂O and functionalized by ethylenediamine (EDA). Carbon dioxide capture was investigated using functional density theory (DFT). Nitrogen (N) doping was confirmed by X-ray photoelectron spectroscopy (XPS), while the thermal characteristics were examined by thermogravimetric analysis (TGA). Surface morphology was examined by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) detection, and surface functional groups were characterized using Fourier-transform infrared (FTIR) spectroscopy. In addition, the inorganic components were characterized by X-ray diffraction (XRD). The best performance of CO₂ adsorption of 1.69 mmol/g was achieved at 0 °C and 1 bar over the adsorbent synthesized at 600 °C with 60 min residence time, a 1:1 degree of impregnation, and a dry preparation method (single-stage preparation). This work presents as a great innovation the use of biomass as a raw material in the adsorption of the main greenhouse gases, using easy and accessible products. Full article

This study presents a structured review of 59 academic articles, identified through an extensive literature survey, focused on the environmental implications of drone-based delivery systems within the broader fields of transportation, logistics, and sustainability. The reviewed journals cover a multidisciplinary range of topics, reflecting the intersection of drone technology with environmental science, logistics management, and operational research. Key journals, such as Transportation Research Part C: Emerging Technologies, Computers and Industrial Engineering, and Applied Mathematical Modelling, offer critical insights into how drone technology can reshape logistics systems, reduce environmental impacts, and contribute to intelligent transportation solutions. In addition, niche publications in areas like artificial intelligence, disaster risk reduction, and sustainable transportation further enhance the breadth of this review. By identifying and categorizing these publications, this review provides a valuable resource for researchers and practitioners aiming to explore the environmental and operational challenges of drone-based delivery systems, while also offering a foundation for future research on their sustainability and integration into existing logistics frameworks. Full article

The major challenges in designing a Hybrid Renewable Energy System (HRES) include selecting appropriate renewable energy sources and storage systems, accurately sizing each component, and defining suitable optimization criteria. This study addresses these challenges by employing Particle Swarm Optimization (PSO) within a multi-criteria optimization framework to design an HRES in Kern County, USA. The proposed system integrates wind turbines (WTS), photovoltaic (PV) panels, Biomass Gasifiers (BMGs), batteries, electrolyzers (ELs), and fuel cells (FCs), aiming to minimize Annual System Cost (ASC), minimize Loss of Power Supply Probability (LPSP), and maximize renewable energy fraction (REF). Results demonstrate that the PSO-optimized system achieves an ASC of USD6,336,303, an LPSP of 0.01%, and a REF of 90.01%, all of which are reached after 25 iterations. When compared to the Genetic Algorithm (GA) and hybrid GA-PSO, PSO improved cost-effectiveness by 3.4% over GA and reduced ASC by 1.09% compared to GAPSO. In terms of REF, PSO outperformed GA by 1.22% and GAPSO by 0.99%. The PSO-optimized configuration includes WT (4669 kW), solar PV (10,623 kW), BMG (2174 kW), battery (8000 kWh), FC (2305 kW), and EL (6806 kW). Sensitivity analysis highlights the flexibility of the optimization framework under varying weight distributions. These results highlight the dependability, cost-effectiveness, and sustainability for the proposed system, offering valuable insights for policymakers and practitioners transitioning to renewable energy systems. Full article

This research analyzes the technical feasibility and implementation of an appropriate technology for the production of briquettes from Pinus spp. waste (sawdust and shavings) in a rural community in Michoacán, Mexico. The results indicate that local small-scale briquette production in the Pichátaro community has the potential to boost a local economy based on the manufacturing and marketing of densified solid biofuels. The design of the manual briquetting machine was developed through a participatory approach with community users. Structural simplicity and locally accessible maintenance were prioritized, the aspects that were addressed little in previous studies. The machine allows for the production of briquettes using a low-cost mixture composed of sawdust and Pinus spp. shavings, corn starch, and water. Based on local conditions and production needs, parameters such as reduced processing times and simplified manufacturing methods were identified as essential to establishing an efficient regional production and supply chain. Furthermore, the valorization of solid waste through the production of alternative biofuels contributes to the diversification of the energy matrix in rural residential sectors and small industries in communities in Mexico. The estimated cost of the machine is USD 75.44, and most of its components are easily replaceable, which favors its sustainability and prolonged use. This study demonstrates that the implementation of a low-pressure briquette system based on appropriate rural technologies represents a viable strategy for the use of wood waste and the promotion of sustainable energy solutions in rural communities. Full article

This research identified the optimal scenarios to produce three bioenergy outputs: dual generation (electricity and heat), electricity, and heat in two regions located in the northern part of Costa Rica. Two biomass conversion technologies—boilers and gasification—with 2, 5, and 10 MW production capacities were assessed to ascertain the most suitable technology-capacity pairing for each bioproduct. To this end, a comprehensive financial model was developed to maximize the net present value. Following this, the equilibrium point for biomass supply and demand was ascertained, alongside estimations of the associated costs and energy utility. The findings indicated that the three bioenergy products could be completed within the local energy market at prices below 0.14 USD/kWh, with maximum supply distances of 90 km. The boiler and turbine technology proved most suitable for dual and electricity generation, with capacities ranging between 2 MW and 5 MW, where differentiation was influenced by biomass transportation. Furthermore, heat generation demonstrated financial viability at a capacity of 2 MW. In the evaluation of supply-demand break-even points, a maximum benefit of 26% was observed, with dual production yielding the highest benefits and heat production being the least favorable option due to the costs linked to biomass transportation and the low efficiency of energy transformation. Full article

Plastic waste poses a significant challenge in Africa and around the world, with its volume continuing to increase at an alarming rate. In Africa, an estimated 25–33% of daily waste is made up of plastic, posing a threat to the environment, marine life, and human health. One potential solution to this problem is waste-to-energy recycling, such as pyrolysis, which involves the conversion of waste materials into oil, char, and non-condensable gasses through a thermochemical process in the absence of oxygen. Given the abundance of waste in Africa and the continent’s energy challenges, pyrolysis offers a sustainable solution. This review delves into the concept of pyrolysis, its products, thermodynamics, and endothermic kinetics, presenting it as a promising way to address the plastic waste problem in Africa. Despite the African Union’s goal to recycle plastic waste, the continent faces significant barriers in achieving this target, including infrastructural, economic, and social difficulties. It is crucial to implement sustainable strategies for managing plastic waste in Africa to mitigate environmental degradation and promote a cleaner and healthier living environment. Pyrolysis technology is highlighted as a viable solution for plastic waste management, as it can convert plastic waste into valuable byproducts such as oil, char, and syngas. Case studies from countries like South Africa and Nigeria demonstrate the potential for scaling up pyrolysis to address waste management issues while generating energy and job opportunities. This review underscores the need for investment, regulatory support, and public awareness to overcome the challenges and unlock the full potential of pyrolysis in Africa. Embracing pyrolysis as a method for managing plastic waste could lead to significant environmental and economic benefits for the continent. Full article

This study was conducted to determine the performance of atmospheric cold plasma (ACP) on powder-form biological materials including wheat flour (WF) and whey protein isolate (WP). Coliform bacteria inactivation and optimization were performed based on a central composite design with two variables, namely residence time and mass of the sample. The results indicated that both variables had a significant effect on bacterial inactivation with more importance of residence time compared to mass of the substrate. The drying process was conducted for selected conditions including mild, moderate, and extreme conditions. The results indicated that plasma can even be used as a fast and effective tool for drying biological materials. Among all models used in this study, the Henderson–Pabis model was more suitable in predicting the dehydration kinetics of both materials. Drying rate constants obtained using this model indicated that the ratios of residence time over mass of the material did not have a significant impact on this parameter. Analysis of the functional properties revealed that water absorption can be highly (≈70%) enhanced in WF. However, properties such as oil absorption (in WF and WP), protein solubility and emulsifying activity index (EAI), and stability (in WP) were slightly changed by the plasma treatment. Full article

This article investigates the performance of Faradaic electro-swing reactive adsorption (ESA) for CO₂ capture using simulations. Traditional methods such as amine scrubbing face energy efficiency challenges, particularly at low CO₂ concentrations. ESA, which uses electricity for CO₂ regeneration, offers a promising alternative due to its isothermal operation and scalability. The study models ESA using quinone-based redox-active CO₂ carriers in an electrochemical cell with an ionic liquid electrolyte, allowing reversible adsorption and release through voltage control. The model estimates system productivity and energy consumption, considering transport and chemical kinetics. Key findings show that operating parameters, such as applied potential and gas flow rate, have a significant effect on efficiency. Applying a potential of −1.3 V improved the adsorption capacity, reducing CO₂ capture time compared to −1.1 V. At a 1% CO₂ concentration and a low flow rate, effective capture resulted in a productivity of 1.6 kg/(m³·day) with an energy consumption of 0.6 MWh/tCO₂. However, higher gas flow rates reduced capture efficiency due to CO₂ transport limitations in the ionic liquid. Optimization of electrode design is essential to improve ESA efficiency. Full article

A new high-temperature allothermal gasification technology is used to process three types of oil waste: ground oil sludge (GOS), tank oil sludge (TOS), and petcoke. The gasifying agent (GA), mainly composed of H₂O and CO₂ at a temperature above 2300 K and atmospheric pressure, is produced by pulsed detonations of a near-stochiometric methane-oxygen mixture. The gasification experiments show that the dry off-gas contains 80–90 vol.% combustible gas composed of 40–45 vol.% CO, 28–33 vol.% H₂, 5–10 vol.% CH₄, and 4–7 vol.% noncondensable C₂–C₃ hydrocarbons. The gasification process is accompanied by the removal of mass from a flow gasifier in the form of fine solid ash particles with a size of about 1 μm. The ash particles have a mesoporous structure with a specific surface area ranging from 3.3 to 15.2 m²/g and pore sizes ranging from 3 to 50 nm. The measured wall temperatures of the gasifier are in reasonable agreement with the calculated value of the thermodynamic equilibrium temperature of the off-gas. The measured CO content in the off-gas is in good agreement with the thermodynamic calculations. The reduced H₂ content and elevated contents of CH₄, CO₂, and C_xH_y are apparently associated with the nonuniform distribution of the waste/GA mass ratio in the gasifier. To increase the H₂ yield, it is necessary to improve the mixing of waste with the GA. It is proposed to mix crushed petcoke with oil sludge to form a paste and feed the combined waste into the gasifier using a specially designed feeder. Full article

As a crucial strategy for mitigating climate change and achieving electricity independence, renewable energy sources (RESs) are gaining widespread importance. This study explores achieving electricity autonomy for Nisyros Island, Greece, through RESs. Four scenarios are evaluated, including standalone wind and photovoltaic systems, alongside hybrid options combining both. Each scenario is designed to meet the island’s electricity demands while considering economic feasibility and minimal environmental impact. The research findings are that wind-based scenarios offer the most cost-effective solutions, with a three wind turbine setup emerging as the most economical option for full coverage of electricity demands. Hybrid approaches, particularly those incorporating more wind turbines, are also financially viable. Real-world consumption data are integrated into the analysis, providing valuable insights for Nisyros’ energy future. Overall, the study demonstrates Nisyros’ potential to achieve electricity independence through RESs, with wind resource assessments suggesting that the island could become autonomous. This approach would promote environmental sustainability by reducing the given dependence on fossil fuels. Additionally, it would bring economic benefits for the island’s residents in the renewable energy sector. Furthermore, this work allows for the island to achieve electricity independence through renewable energy in alignment with the EU’s climate goals. Full article

The Mediterranean region faces significant water scarcity, a challenge intensified by climate change, impacting both agricultural productivity and water quality. High sodium levels in irrigation water compromise soil structure, leading to reduced crop yields and economic strain. This study investigates the use of sustainable adsorbents derived from agricultural residues (almond shell, eggshell, and pumice) for the removal of sodium from irrigation water. These materials, widely available in the Mediterranean, support circular economy principles by repurposing biowaste to address agricultural challenges. Adsorption experiments were conducted using real irrigation water, capturing the complexity of its physicochemical properties to evaluate the effectiveness of these biosorbents under practical conditions. A Central Composite Rotational Design (CCRD) was applied to optimize adsorption parameters, focusing on adsorbent concentration, agitation, and contact time. Kinetic studies indicated that sodium adsorption adhered to a pseudo-second order model, suggesting a chemically controlled process. Isotherm analysis, with a strong fit to the Jovanovic model, confirmed a predominantly monomolecular adsorption mechanism across all adsorbents, while the Freundlich model highlighted site heterogeneity. Microscopy and energy-dispersive X-ray spectroscopy (EDX) revealed structural modifications in the adsorbents before and after treatment. The porous internal structure of the almond shell displayed significant sodium retention, while the calcified eggshell surface showed high initial adsorption efficiency but rapid site saturation. Pumice, noted for its extensive porosity, sustained adsorption capacity even with surface deposits formed during treatment. This research demonstrates the potential of biowaste-derived adsorbents for efficient sodium removal from complex aqueous systems, offering a viable solution for sustainable agriculture and improved soil and water management in Mediterranean regions. Full article

This study aims to better harness the geothermal potential of Mount Meager in British Columbia, a premier reserve of geothermal resources in Canada. Numerical investigations explore the feasibility and optimization of an Enhanced Geothermal System to boost geothermal energy extraction capabilities. Utilizing COMSOL Multiphysics, the model simulates non-isothermal fluid flow and heat transfer through complex subsurface geology with discrete fracture planes. The sensitivity analyses assess the impact of various operational parameters, including injection strategies, reservoir characteristics, and wellbore configurations on heat extraction efficiency. These analyses indicate that a higher injection rate, lower injection temperatures, and optimized fracture areas significantly enhance system performance by maximizing thermal energy capture and minimizing thermal breakthrough. Additionally, specific wellbore configurations, particularly the triplet setup with deeper depth, significantly improve geothermal fluid circulation and heat extraction compared to doublet configurations at shallower depths. This study reveals that the base case scenario of the EGS could generate approximately $8.311\times {10}^9$ kWh over 30 years, while optimization strategies could elevate potential production to up to $16.68\times {10}^9$ kWh. These findings underscore the critical role of carefully designed operational strategies that leverage local geological and thermal characteristics to optimize geothermal systems, thereby enhancing efficiency and promoting sustainable energy development at Mount Meager. Full article

Since 2019, the NextGen pilot wastewater treatment unit—also known as the NextGen Sewer Mining concept—has been operating at the Athens Plant Nursery, transforming sewage from Athens’ central network into irrigation water and compost. This unit produces resources for plant growth through membrane bioreactors (MBRs) and aerobic sludge digestion. This study experimentally evaluates the effects of NextGen reused water and compost on two common ornamental plant species in Athens, Pittosporum tobira (Angelica) and Myrtus communis (Common Myrtle), compared to the use of tap water and red soil without additional fertilization. The results indicate that NextGen reused water combined with compost significantly promotes both height and weight growth in these plants. However, by the end of the experiment, compost fertilization had a greater effect on the height and weight growth of both Angelica and Myrtus plants when applied independently and watered with tap water, compared to the use of NextGen reused water combined with red soil. Notably, none of the 96 plants withered throughout the experiment, indicating that promising and sustainable technologies like the concept of Sewer Mining can effectively replace conventional and environmentally outdated methods of plant nutrition and irrigation by producing reused water and compost. Full article

Vehicle washing facilities (VWFs) consume substantial amounts of potable water and produce wastewater containing pollutants such as hydrocarbons, detergents, and pathogens, presenting significant environmental and operational challenges. This study evaluates Nature-based Solutions (NbS) for wastewater treatment and recycling at a pilot facility in Girona, Spain, aiming to reduce potable water consumption and ensure safe reuse while minimizing environmental impact. Over a two-year period, three systems—a Vertical Flow Treatment Wetland (VFTW), Horizontal Flow Treatment Wetland (HFTW), and Infiltration-Percolation (IP) filter—were tested. Thirty-two parameters, including physicochemical (e.g., turbidity, nutrients, heavy metals, detergents) and microbiological indicators (e.g., E. coli, Legionella spp.), were monitored. VFTW and IP systems were the most effective, reducing turbidity below 5 NTU, COD to under 20 mg/L, and E. coli below 10 CFU/100 mL, meeting Spanish reuse standards. The HFTW effectively removed organic matter and nutrients but faced challenges such as clogging and reduced hydraulic performance, making it less suitable for carwash wastewater. Together, these systems enabled up to 60% water reuse, with final chlorination ensuring microbial safety, particularly against Legionella, while meeting Spanish reuse standards. This study highlights the potential of NbS as sustainable, low-energy solutions for wastewater recycling and pollution control in vehicle washing facilities. Full article

Plastic products are used in agriculture to increase crop yield and improve crop quality to face a double challenge: a growing world population and a depletion and scarcity of natural resources. In this framework, the European Commission is working on establishing biodegradation criteria under natural conditions for certain plastic products. Such criteria are particularly important for products where biodegradation is key once reaching the end of their shelf life, considering an end-of-life scenario where their waste management is either unfeasible or highly complex. Under this scope, this work aims to provide a comprehensive assessment of the current status of European regulations in terms of plasticulture product biodegradability, highlighting the specific tests and standards regarding the biodegradability assessment. Biodegradation of plasticulture products in soil and water has been considered for biodegradability criteria, establishing a threshold of at least 90% of the organic carbon converted into CO₂. These regulations have followed a tool-based study of a mathematical prediction model for the main existing families of biodegradable polymers in soil. These regulations will help the fertilizer industry to develop new formulations that are more sustainable and effective in the agriculture field. Full article

Microalgae have attracted wide attention due to their extensive application potential. Dewatering is a necessary work for the application of microalgae, especially in biofuel production, where forward osmosis (FO) research is relatively advanced but still faces technical bottlenecks hindering large-scale commercialization. Based on the current research in recent years, the research progress in the causes and control of membrane fouling, the development of membrane materials and optimization of membrane structure, and the energy saving and efficiency of the process are reviewed in this paper. We found that different species of algae have direct effects on membrane fouling. Chlorella vulgaris has a low membrane fouling trend, but the mechanisms of fouling need further investigation. The material development and structure optimization of membranes are the main research methods to reduce membrane fouling, but there are still some defects, such as complicated preparation and low water flux, which are difficult to apply on a large scale. The research progress of reducing costs by using seawater, urine, fertilizer, etc. as new draw solutions (DS) is reviewed. At present, many aspects of FO microalgae dewatering technology are still not well understood, and future research should focus on scaling up the existing technologies. Full article

Heat stress on workers wearing PPE (Personal protective equipment) in hot outdoor environments is of rising concern, especially in cases when rest breaks and clothing changes are impractical. Mist fan evaporative cooling could provide low-energy continuous cooling, even during work activity. The cooling effect of a misting fan was compared to that of a fan alone, as well as natural convection. A thermal mannequin with heat flux sensors at eight body locations was exposed to an outdoor misting fan while being clothed in typical work clothes and PPE. Work clothes were dry or saturated with water to simulate sweat. The distance from the misting fan ranged from 4 m (wetting common) to 7 m (wetting unlikely). On average, the misting fan had a cooling effect of 0.31 met (18.3 W/m²) higher than natural convection when PPE is worn with wet work clothes, and 0.35 met (20.3 W/m²) higher than when PPE is worn with dry work clothes. This equates to reducing the thermal metabolic load from light industrial work to walking about in office work, or from standing to reclining. Under the ISO 7243 international standard for workers in hot environments, this would increase the acceptable WBGT (wet bulb globe temperature) by over 0.6 °C. Full article

Pore-scale remediation investigation of oil-contaminated soil is important in several environmental and industrial applications, such as quick responses to sudden accidents. This work aims to investigate the oil pollutant removal process and optimize the oil-contaminated soil remediation performance at the pore scale to find the underlying mechanisms for oil removal from soil. The conservative forms of the phase-field model and the non-Newtonian power-law fluid model are employed to track the moving interface between two immiscible phases, and oil pollutant flushing removal process from soil pores is investigated. The effects of viscosity, interfacial tension, wettability, and flushing velocity on pore-scale oil pollutant removal regularity are explored. Then, the oil pollutant removal effects of two flushing agents (surfactant system and surfactant–polymer system) are compared using an oil content prediction curve based on UV-Visible transmittance. The results show that the optimal removal efficiency is obtained for a weak water-wetting system with a contact angle of 60° due to the stronger two-phase fluid interaction, deeper penetration, and more effective entrainment flow. On the basis of the dimensionless analysis, a relatively larger flushing velocity, resulting in a higher capillary number (Ca) in a certain range, can achieve rapid and efficient oil removal. In addition, an appropriately low interfacial tension, rather than ultra-low interfacial intension, contributes to strengthening the oil removal behavior. A reasonably high viscosity ratio (M) with a weak water-wetting state plays synergetic roles in the process of oil removal from the contaminated soil. In addition, the flushing agent combined with a surfactant and polymer can remarkably enhance the oil removal efficiency compared to the sole use of the surfactant, achieving a 2.5-fold increase in oil removal efficiency. This work provides new insights into the often-overlooked roles of the pore scale in fluid dynamics behind the remediation of oil-contaminated soil via flushing agent injection, which is of fundamental importance to the development of effective response strategies for soil contamination. Full article

To develop a biomass and power-to-gas (BPtG) process for renewable electricity storage and sustainable synthetic natural gas (SNG) production, this work investigated five BPtG processes integrated with different electricity-driven gasification technologies based on simulation data. These processes were evaluated for SNG composition and yield, life-cycle energy and exergy efficiencies, life-cycle carbon emissions, and the equivalent unit production cost. The results show that the energy and exergy efficiencies of SNG from those processes range between 53.1 and 58.6% and 36.4 and 41.1%, respectively. Based on the energy allocation method, the carbon emissions without and with CO₂ capture ranges from 22.0 to 34.8 and from −43.4 to −17.6, respectively, in gCO₂e/MJ_SNG. These BPtG processes can produce low-carbon SNG and even achieve negative carbon emissions with CO₂ capture. Both feedstock and electricity costs have significant influences on the profitability of the processes. The BPtG process integrated with resistance heating gasification, plasma-assisted gasification, and moderate water electrolysis are recommended for their compromise of multi-perspective performances. This paper provided the orders of the five processes based on these indicators and recommendations for different applicable scenarios. Full article

Cruise ships function as a means of transport while simultaneously accommodating thousands of guests, providing a holiday experience with various entertainment options. This translates to high energy requirements for propulsion and hotel operations, typically covered by the combustion of fossil fuels. The operation of cruise vessels with fossil fuels contributes to carbon dioxide and also local harmful emissions in ports when shore power connections are not available. To enable cleaner and sustainable cruising, alternative technologies and fuels must be adopted. The present study evaluated the applicability of hydrogen fuel in combustion engines in a Meraviglia-class cruise ship. The fuel consumption of the ship was based on a real operation in Europe. This study examined how fuel energy in the form of LH₂ could be stored on the ship for a European cruise route and concludes that 3700 m³ of storage space would be needed to accommodate the liquid hydrogen. The mass of the LH₂ would only be one-third of that of fossil fuels, but the weight of the LH₂ tanks would most likely increase the total weight of the hydrogen storage. Additional new technologies and combined power production could significantly reduce the amount of LH₂ to be stored. Full article

This study assesses supply risks for critical raw materials (CRMs) essential to Europe’s thermoelectric (TE) technology, which transforms heat into electricity. Given the EU’s heavy reliance on imports for key materials like tellurium, antimony, bismuth, and lead, the analysis incorporates market forecasting, scarcity quantification, and Monte Carlo simulations to model demand and supply risks. This study reveals that tellurium poses high risks due to scarcity and potential geopolitical impacts, with antimony and bismuth at moderate risk, and lead presenting notable health hazards. The findings suggest the necessity of circular supply chains and material alternatives to mitigate resource, environmental, and geopolitical challenges for sustainable TE development in Europe. Moreover, there is a pressing need to update and expand data availability for materials like tellurium to enable more robust risk assessments in the immediate future. Full article

This study analyzed the anaerobic co-digestion of inoculum (I), rubber plant effluent (RPE) and Gliricidia leaves slurry (GLS) at different mixing ratios for the simultaneous production of methane and organic fertilizer. The results were analyzed for volatile fatty acids, pH, C/N ratio, and methane production. The organic quality of the substrate mixture before and after anaerobic digestion was analyzed for total organic carbon, total nitrogen, potassium, and phosphorus contents. This study concluded that the inoculum, rubber plant effluent (RPE), and Gliricidia leaves slurry (GLS) mixed at the ratio of 10:2:2 showed higher methane production than other experiments conducted at different mixing ratios. The nitrogen, potassium, and phosphorus contents of the substrates were increased after anaerobic digestion. However, the organic carbon content in the substrate decreased in all experiments. This research recommends the planting of rubber trees and Gliricidia maculata to promote energy sustainability and the socio-economic development of Mauritania. Full article

In this study, vapor–liquid equilibrium (VLE) experimental data were measured for two binary solvents based on 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU), which can be used as a new CO₂-binding organic liquids (CO₂-BOLs) solvent. No experimental data are available in the literature and are fundamental to determine whether the considered mixtures are suitable to be possible alternatives to traditional amine solutions for CO₂ removal. The bubble point data of 1,2-propanediol+1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) and 1,4-butanediol+DBU mixtures were measured at 30 kPa. The experimental determination was carried out in an all-glass dynamic recirculation still at the Process Thermodynamics laboratory (PT lab) of Politecnico di Milano. The thermodynamic modeling of the VLE behavior of two DBU-based mixtures was performed considering the NRTL, the UNIQUAC, and the Wilson models, and binary interaction parameters of the NRTL activity coefficients model were regressed on the basis of the measured experimental data. Full article

Strontium (⁹⁰Sr) is a typical radionuclide, which can act as a contaminant and poses a big problem for the eco-environment if left untreated. In this study, an original nitrogen-doped calcite (N-CaCO₃) was synthesized using a solvothermal and calcination method and used to remove Sr(II) from simulated water. XRD, SEM, and XPS analyses proved that N was successfully doped into CaCO₃, resulting in porous CaCO₃ with a regular morphology. The specific surface area of N-CaCO₃ (136.53 m²/g) can reach 2.19-fold greater than that of CaCO₃. The results based on the batch adsorption data indicated that the pseudo-second-order kinetic model (R² = 0.9964) and the ion exchange model (R² = 0.9859) fitted the adsorption data well. The as-synthesized N-CaCO₃ exhibited better adsorption performance in regard to low concentrations of Sr(II) (below 64.5 mg/L) compared with commercial CaCO₃. The structural analysis suggested that Ca and N played pivotal roles in the adsorption process and that the adsorption mechanism was dominated by ion exchange and surface complexation. This study successfully fabricated a nitrogen-doped calcite for Sr(II) cleanup, presenting an efficient strategy to modulate the microstructure of CaCO₃, or other materials, to enhance its adsorption performance. Full article

This study investigates the potential of utilizing livestock waste and vineyard residues for sustainable energy production in Portugal. Through the physical and chemical characterization of swine waste, grape seeds and skins, cork powder, sawdust, and biochar, 53 distinct samples, including 11 individual biomasses and their derived mixtures, were analyzed to identify optimal combinations for biofuel pellet production. The best-performing mixture, composed of 50% swine waste, 25% grape seeds and skins, and 25% cork powder, achieved a Lower Heating Value (LHV) of 18.34 MJ/kg and low ash content, qualifying it as a class B pellet. This mixture offers significant energy potential while minimizing environmental impacts. The research also presents three energy valorization scenarios, with the most balanced scenario meeting up to 6% of Portugal’s electricity demand and providing energy savings equivalent to 485,463 tons of oil equivalent (toe) annually. A case study on a “Case Study Farm” in the Douro region, managing 2000 pigs and producing 500 tons of wine grapes annually, demonstrated that implementing the optimal biomass mixture could generate 3854 MWh of heat and 1156 MWh of electricity per year. This could result in annual revenues of EUR 189,258 from pellet sales, covering the initial investment of EUR 283,938 within 6.36 years, with a total surplus of EUR 689,666 over 20 years. These findings highlight the economic viability and environmental benefits of converting agricultural waste into renewable energy, contributing to Portugal’s carbon neutrality and reducing energy dependence. Full article