Search Results (159)

Plastic streams dominated by polyethylene (PE) including PE HD/MD (High Density/Medium Density) and PE LD/LLD (Low Density/Linear Low Density), polypropylene (PP), and polyvinyl chloride (PVC) across Europe demand a design framework that links synthesis with end of life reactivity, supporting circular economic goals and European Union waste management targets. This work integrates polymerization derived chain architecture and depolymerization mechanisms to guide selective valorization of commercial plastic wastes in the European context. Catalytic topologies such as Bronsted or Lewis acidity, framework aluminum siting, micro and mesoporosity, initiators, and strategies for process termination are evaluated under relevant variables including temperature, heating rate, vapor residence time, and pressure as encountered in industrial practice throughout Europe. The analysis demonstrates that polymer chain architecture constrains reaction pathways and attainable product profiles, while additives, catalyst residues, and contaminants in real waste streams can shift radical populations and observed selectivity under otherwise similar operating windows. For example, strong Bronsted acidity and shape selective micropores favor the formation of C₂ to C₄ olefins and Benzene, Toluene, and Xylene (BTX) aromatics, while weaker acidity and hierarchical porosity help preserve chain length, resulting in paraffinic oils and waxes. Increasing mesopore content shortens contact times and limits undesired secondary cracking. The use of suitable initiators lowers the energy threshold and broadens processing options, whereas diffusion management and surface passivation help reduce catalyst deactivation. In the case of PVC, continuous hydrogen chloride removal and the use of basic or redox co catalysts or ionic liquids reduce the dehydrochlorination temperature and improve fraction purity. Staged dechlorination followed by subsequent residue cracking is essential to obtain high quality output and prevent the release of harmful by products within European Union approved processes. Framing process design as a sequence that connects chain architecture, degradation chemistry, and operating windows supports mechanistically informed selection of catalysts, severity, and residence time, while recognizing that reported selectivity varies strongly with reactor configuration and feed heterogeneity and that focused comparative studies are required to validate quantitative structure to selectivity links. In European post consumer sorting chains, PS and PC are frequently handled as separate fractions or appear in residues with distinct processing routes, therefore they are not included in the polymer set analyzed here. Polystyrene and polycarbonate are outside the scope of this review because they are commonly handled as separate fractions and are typically optimized toward different product slates than the gas, oil, and wax focused pathways emphasized here. Full article

Uniform application of fertilizers and pesticides continues to dominate global agriculture despite significant spatial variability in soil and crop conditions. This mismatch results in avoidable yield gaps, excessive chemical waste, and environmental pressures, including nutrient leaching and greenhouse gas emissions. The integration of Artificial Intelligence (AI) and Remote Sensing (RS) has emerged as a transformative framework for diagnosing this variability and enabling site-specific, climate-responsive management. This systematic synthesis reviews evidence from 2000–2025 to assess how AI–RS technologies optimize agrochemical efficiency. A comprehensive search across Scopus, Web of Science, IEEE Xplore, ScienceDirect, and Google Scholar were used. Following rigorous screening and quality assessment, 142 studies were selected for detailed analysis. Data extraction focused on sensor platforms (Landsat-8/9, Sentinel-1/2, UAVs), AI approaches (Random Forests, CNNs, Physics-Informed Neural Networks), and operational outcomes. The synthesized data demonstrate that AI–RS systems can predict critical soil attributes, specifically salinity, moisture, and nutrient levels, with 80–97% accuracy in some cases, depending on spectral resolution and algorithm choice. Operational implementations of Variable-Rate Application (VRA) guided by these predictive maps resulted in fertilizer reductions of 15–30%, pesticide use reductions of 20–40%, and improvements in water-use efficiency of 25–40%. In fields with high soil heterogeneity, these precision strategies delivered yield gains of 8–15%. AI–RS technologies have matured from experimental methods into robust tools capable of shifting agrochemical science from reactive, uniform practices to predictive, precise strategies. However, widespread adoption is currently limited by challenges in data standardization, model transferability, and regulatory alignment. Future progress requires the development of interoperable data infrastructures, digital soil twins, and multi-sensor fusion pipelines to position these technologies as central pillars of sustainable agricultural intensification. Full article

Biogas upgrading and bottling represent essential processes in transforming raw biogas produced via the anaerobic digestion of organic waste into high-purity biomethane (≥95% CH₄), a renewable energy source suitable for applications in cooking, transportation, and electricity generation. Upgrading technologies, such as membrane separation, pressure swing adsorption (PSA), water and chemical scrubbing, and emerging methods, like cryogenic distillation and supersonic separation, play a pivotal role in removing impurities like CO₂, H₂S, and moisture. Membrane and hybrid systems demonstrate high methane recovery (>99.5%) with low energy consumption, whereas chemical scrubbing offers superior gas purity but is limited by high operational complexity and cost. Challenges persist around material selection, safety standards, infrastructure limitations, and environmental impacts, particularly in rural and off-grid contexts. Bottled biogas, also known as bio-compressed natural gas (CNG), presents a clean, portable alternative to fossil fuels, contributing to energy equity, greenhouse gases (GHG) reduction, and rural development. The primary aim of this research is to critically analyze and review the current state of biogas upgrading and bottling systems, assess their technological maturity, identify performance optimization challenges, and evaluate their economic and environmental viability. The research gap identified in this study demonstrates that there is no comprehensive comparison of biogas upgrading technologies in terms of energy efficiency, price, scalability, and environmental impact. Few studies directly compare these technologies across various operational contexts (e.g., rural vs. urban, small vs. large scale). Additionally, the review outlines insights into how biogas can replace fossil fuels in transport, cooking, and electricity generation, contributing to decarbonization goals. Solutions should be promoted that reduce methane emissions, lower operational costs, and optimize resource use, aligning with climate targets. This synthesis highlights the technological diversity, critical barriers to scalability, and the need for robust policy mechanisms to accelerate the deployment of biogas upgrading solutions as a central component of a low-carbon, decentralized energy future. Full article

Municipal solid waste (MSW) recycling is constrained by contamination, heterogeneity, and infrastructure built around material-specific pathways. We introduce effectiveness-normalized greenhouse gas (GHG) emissions as a system-level metric that adjusts reported process burdens by feedstock eligibility (Effectiveness Fraction, EF) and carbon recovery efficiency (CRE) to reflect real-world MSW conditions. Using published LCA data and engineering estimates, we benchmark six pathways, mechanical recycling, PET depolymerization, enzymatic depolymerization, pyrolysis, supercritical water gasification (SCWG), and Regenerative Robust Gasification (RRG), at the scale of mixed MSW. Normalizing for EF and CRE reveals large differences between process-level and system-level performance. Mechanical recycling and PET depolymerization show low process intensities yet high normalized impacts because they can treat only a small share of plastics in MSW. SCWG performs well at broader eligibility. RRG, a plasma-assisted molten-bath approach integrated with methanol synthesis, maintains the lowest normalized impact (~1.6 t CO₂e per ton of recycled polymer) while accepting virtually all organics in MSW and vitrifying inorganics. Modeled methanol yields are ~200–300 gal·t⁻¹ without external hydrogen and up to ~800 gal·t⁻¹ with renewable methane reforming. The metric clarifies trade-offs for policy and investment by rewarding technologies that maximize diversion and carbon retention. We discuss how effectiveness-normalized results can be incorporated into LCA practice and Extended Producer Responsibility (EPR) frameworks and outline research needs in techno-economics, regional scalability, hydrogen sourcing, and uncertainty analysis. Findings support aligning infrastructure and procurement with robust, scalable routes that deliver circular manufacturing from heterogeneous MSW. Full article

Syngas fermentation is a promising carbon capture and utilization (CCU) technology for producing carboxylic acids while transforming low-cost waste gas into high-value products. This study evaluates the two bioreactor feeding strategies for synthesis gas (syngas) fermentation by Eubacterium callanderi (formerly Butyribacterium methylotrophicum) strain Marburg—on-demand feeding (ODF) and continuous feeding (CF)—with a synthetic syngas mixture of 23 vol% CO₂, 29 vol% CO, 32 vol% H₂, and 16 vol% CH₄, mimicking the syngas from lignocellulosic gasification. The ODF assay achieved a maximum syngas consumption rate of 112 mL/h, yielding 24.1 g/L acids, namely 22.9 g/L acetate and 1.3 g/L butyrate. CF of syngas at 223 mL/h required more gas (62.9 L) to produce 22.7 g/L total acids, from which 19.0 g/L acetate and 3.7 g/L butyrate were achieved. The CF-specific production rate (g_product/g_{dry_cell_weight}/hour) reached 0.5 g/g_DCW/h (acetate) and 0.17 g/g_DCW/h (butyrate), outperforming ODF with 0.3 and 0.02 g/g_DCW/h, respectively. ODF minimized gas wastage and enabled CH₄ accumulation inside the bioreactor up to approximately 78 vol%, while CF led to CO₂ accumulation, indicating a need for more efficient CO₂ utilization strategies, such as sequential fermentations. This work highlights the critical impact of the two feeding options studied with regard to scaling up the carbon-efficient production of carboxylic acids, and indicates that both strategies can have potential applications. ODF is ideal for increasing carbon fixation and achieving, simultaneously, gas cleaning, while CF fermentations are better suited to maximizing the acid production rate. Full article

The Mediterranean Diet (MD) is globally recognized not only for its well-established benefits to human health but also for its potential as a sustainable dietary model from environmental perspectives. Primarily based on plant-based foods, olive oil, fish, and seasonal and local products, the MD stands out for its ability to reduce overall mortality and the incidence of chronic diseases. At the same time, it is a low environmental impact dietary approach, contributing to the reduction in greenhouse gas emissions, water savings, biodiversity conservation, and soil regeneration. This narrative review was conducted by searching the Scopus and PubMed databases, covering all publications up to 2011, applying predefined inclusion and exclusion criteria, and ultimately including 33 studies. The paper provides a synthesis of the key elements that make the MD a paradigm of sustainability, analyzing critical indicators such as carbon, water, and energy footprints, land use, food waste generation, and carbon sequestration. It also addresses the decline in adherence to the MD, even in Mediterranean countries, highlighting the socio-economic, cultural, and behavioral causes, as well as the necessary strategies to promote its rediscovery and adaptation to contemporary contexts. Full article

Fly ash from coal-fired power plants is a promising precursor for zeolite synthesis due to its aluminosilicate-rich composition. However, its direct utilization is often limited by impurities and a low silicon-to-aluminum ratio (SAR). This study demonstrates the conversion of Class C fly ash from the Soma thermal power plant (Turkey) into FAU- and CHA-type zeolites through optimized acid leaching and hydrothermal synthesis. Acid treatment increased the SAR from 1.33 to 2.85 and effectively reduced calcium-, sulfur-, and iron-bearing impurities. The SAR enhancement by acid leaching was found to be reproducible among Class C fly ashes, whereas Class F materials exhibited a limited response due to their acid-resistant framework. Subsequent optimization of alkaline fusion-assisted synthesis enabled selective crystallization of FAU and CHA, while GIS and MER appeared under prolonged crystallization or higher alkalinity. SEM revealed distinct morphologies, with MER forming rod-shaped clusters, and CHA exhibiting disc-like aggregates. Water sorption analysis showed superior uptake for metastable FAU (~23 wt%) and CHA (~18 wt%) compared to stable GIS and MER (~12–13 wt%). Overall, this study establishes a scalable and sustainable route for producing high-performance zeolites from industrial fly ash waste, offering significant potential for adsorption-based applications in dehumidification, heat pumps, and gas separation. Full article

Global agriculture faces the twin challenges of meeting rising food demand while minimizing environmental impacts, necessitating transformative approaches to nutrient management. Recycled nitrogen fertilizers (RNFs), derived from diverse organic and waste sources such as urine, manure, compost, digestate, biosolids, and struvite, offer a groundbreaking pathway to close nutrient loops, reduce reliance on synthetic inputs, and foster regenerative agroecosystems. This comprehensive review synthesizes peer-reviewed studies published over the last two decades, selected based on relevance, study quality, and applicability to agronomic and environmental outcomes. Unlike earlier reviews that focus on individual RNF types, this work provides a novel cross-sectoral synthesis linking agronomic performance, environmental trade-offs, and socio-economic feasibility within the regenerative agriculture framework. Using a structured analytical framework, we critically assess RNF technologies and applications across agronomic efficacy, ecological implications, economic viability, and socio-regulatory landscapes. Despite promising benefits, including enhanced soil health, greenhouse gas mitigation, and alignment with circular economy principles, widespread RNF adoption remains constrained by logistical complexities, variable nutrient quality, regulatory uncertainties, and social acceptance challenges. By integrating multidisciplinary evidence and identifying system-level synergies and bottlenecks, this review advances a unified understanding of how RNFs can be strategically scaled in regenerative agricultural systems. Key knowledge gaps and integrated research and policy strategies are identified to unlock the full potential of RNFs. Embracing recycled nitrogen within tailored, context-sensitive frameworks has the potential to revolutionize sustainable agriculture, delivering resilient food systems, restoring ecosystem services, and advancing global climate goals. Full article

When renewable resources such as biomass, waste, or carbon dioxide together with renewable electrical energy are used, Fischer–Tropsch (FT) synthesis is a promising option for the sustainable production of fuels and petrochemicals conventionally derived from crude oil. As such renewable resources generally do not occur in large point sources like fossil fuels, future sustainable FT facilities will likely be substantially smaller in scale than their fossil counterparts, which will have a significant impact on their design. A core topic in the reimagination of such smaller-scale facilities will be the reduction in complexity of the FT gas loop. To this end, three simple gas loop designs for the conversion of syngas from biomass gasification were conceived, simulated in DWSIM, and compared regarding their performance. Concepts only employing an internal recycle were found to be inherently limited in terms of efficiency. To achieve high efficiencies, an external recycle with a tail gas reformer and high tail gas recycling ratios (>3) were required. Thereby, the carbon dioxide content of the syngas had a considerable influence on the required syngas H₂/CO ratio, making the separation efficiency of the carbon dioxide removal unit a suitable control parameter in this respect. Full article

This study investigates the valorization of refuse-derived fuel (RDF), waste glass, and mill scale for sustainable ferrosilicon alloy production, contributing to zero-waste practices. RDF was blended with anthracite at ratios of 100, 90, 80, 70, 60 and 50 wt% (designated R1–R6) and applied as a reducing agent in the carbothermic reduction of SiO₂ and Fe₂O₃, thereby decreasing reliance on conventional fossil-based reductants. Ferrosilicon synthesis was conducted at 1550 °C using glass–mill scale blends with reducing agents R1–R6, producing samples named blends A–F. XRD analysis confirmed that the metallic products consisted predominantly of the FeSi intermetallic phase, with characteristic (110) and (310) peaks at 2θ ≈ 45.02° and 78°. The metallic products appeared as numerous small, shiny droplets, with yields ranging from 14.85 to 19.47 wt%; blends D–F exhibited the highest yields. In contrast, blends A–C produced metals with higher Si contents (23.34–27.11 wt%) due to enhanced SiO₂ reduction and efficient Si incorporation into the Fe matrix. Gas analysis and oxygen removal showed that blend B achieved the highest CO generation and reduction extent. Cl removal during RDF heat treatment indicated minimal potential for dioxin and furan formation. Overall, blends A and C were identified as optimal, providing high Si content, satisfactory metallic yield, and reduced CO/CO₂ emissions, demonstrating the effectiveness of RDF-based carbons for environmentally friendly ferrosilicon production. Full article

Biomass gasification, a thermochemical conversion process that turns organic feedstocks like wood, agricultural residues, and solid waste into a combustible gas known as synthesis gas (syngas), is the focus of this study. In this study, Aspen Plus^® as a process simulation platform to optimize key operational parameters for the gasification of sugarcane bagasse was employed. The results are promising, with an equivalence ratio (ER) of 0.25 and a carbon conversion efficiency (XC) of 62.44% achieved, indicating the potential for the produced syngas to be compatible with injection into natural gas distribution networks. The lower heating value (LHV) of the syngas was determined to be 3.93 MJ·kg⁻¹, with an overall gasification efficiency of 49.85%. The simulation results showed strong agreement with experimental data, validating the modeling approach as a reliable predictive tool for biomass gasification systems and reducing unnecessary resource consumption. This validation instills trust and confidence in the reliability of our findings. Full article

The integrated process of CO₂ hydrogenation and catalytic methanol synthesis under plasma conditions holds great potential for CO₂ conversion from waste gases. This process connects a dielectric barrier discharge (DBD) plasma reactor and a methanol synthesis fixed-bed reactor through a pressurization device, achieving the stepwise conversion of CO₂ to CO and then to methanol, thereby establishing a low-carbon and high-efficiency energy conversion system. This study experimentally investigated the key parameters influencing the CO₂ hydrogenation process in the DBD plasma reactor and the methanol synthesis process in the fixed-bed reactor. The results show that in the plasma reaction, discharge power, discharge gap, gas flow rate, and gas composition significantly affect CO₂ conversion efficiency. In the methanol synthesis process, the CO/CO₂ mixed feed exhibits superior catalytic performance compared to pure CO₂. The optimal operating conditions for the integrated process are a plasma voltage of 40 V and a downstream reaction temperature of 240 °C, under which the system achieves the best overall performance. Full article

As landfill mining becomes more widely applied, growing attention is being paid to the waste-to-energy conversion of landfill waste. Co-disposal of landfill waste with municipal solid waste represents one of the primary strategies for achieving energy recovery of landfill waste. In this paper, the emission characteristics of pollutants were systematically analyzed during the co-disposal of landfill waste and municipal solid waste in a full-scale municipal solid waste incineration. The study investigated the formation patterns of toxic PCDD/Fs and gaseous pollutants under different co-disposal ratios of landfill waste (0%, 15%, 25%, 35%, and 45%). In total, 136 PCDD/Fs were analyzed to investigate the influence of co-disposal ratios on PCDD/F formation in both flue gas and fly ash. The influence of varying co-disposal ratios on the phase and elemental composition of fly ash was also investigated. Co-disposal led to a significant reduction in the toxic PCDD/F concentration at the boiler outlet, mainly attributed to the higher sulfur content of LW compared to MSW. With increasing co-disposal ratios, the annual emission amounts of toxic PCDD/Fs in fly ash significantly increased. The ∑PCDD/∑PCDF ratio in both flue gas of boiler outlet and fly ash also increased, indicating an enhancement of the precursor formation pathway, while the de novo synthesis pathway was relatively suppressed. The fly ash exhibited a high proportion of highly chlorinated dioxins (degree of chlorination: 7.19–7.23), likely due to their low saturated vapor pressure. According to the Hagenmaier congener distribution, high co-disposal ratios (25–45%) suppressed the chlorination of DD/DF in fly ash but promoted the formation of gas-phase PCDFs. Different co-disposal ratios significantly influenced both the emission concentrations and removal efficiencies of air pollutants, including NOx, SO₂, and HCl. Although co-disposal did not alter the crystalline phase composition of fly ash, it led to an increased content of heavy metals such as Cu, Hg, and Pb. Full article

The exponential growth of lithium-ion battery consumption has amplified the urgency of identifying sustainable and economically viable recycling solutions. This study proposes an integrated decision-making framework based on the T-Spherical Fuzzy Einstein Interaction Aggregator DEMATEL-CoCoSo approach to comprehensively evaluate and rank battery recycling technologies under uncertainty. Ten key evaluation criteria—encompassing environmental, economic, and technological dimensions—were identified through expert consultation and literature synthesis. The T-Spherical Fuzzy DEMATEL method was first applied to analyze the causal interdependencies among criteria and determine their relative weights, revealing that environmental drivers such as energy consumption, greenhouse gas emissions, and waste generation exert the most systemic influence. Subsequently, six recycling alternatives were assessed and ranked using the CoCoSo method enhanced by Einstein-based aggregation, which captured the complex interactions present in the experts’ evaluations and assessments. Results indicate that Direct Recycling is the most favorable option, followed by the Hydrometallurgical and Bioleaching methods, while Pyrometallurgical Recycling ranked lowest due to its high energy demands and environmental burden. The proposed hybrid model effectively handles linguistic uncertainty, expert variability, and interdependent evaluation structures, offering a robust decision-support tool for sustainable technology selection in the circular battery economy. The framework is adaptable to other domains requiring structured expert-based evaluations under fuzzy environments. Full article

The escalating demand for sustainable and eco-friendly production processes has necessitated the exploration of renewable resources for the synthesis of valuable chemicals. This study investigated the fermentative synthesis of gluconic acid (GA) and xylonic acid (XA) from hydrolyzed palm fronds by using Gluconobacter oxydans. The key variables examined included agitation speed, inoculum ratio, and composition of fermentation media. In a synthetic medium, maximum GA concentration reached 52.82 ± 12.88 g/L at 65 h using 150 rpm agitation and 15% (v/v) inoculation, while maximum XA concentration achieved 2.31 ± 1.43 g/L at 96 h using 220 rpm agitation and 9% (v/v) inoculation. In the hydrolysate medium, the maximum GA concentration was 3.24 ± 0.66 g/L at fermentation onset using 220 rpm agitation and 15% (v/v) inoculation, while the maximum XA concentration reached 0.62 ± 0.04 g/L at 24 h using 190 rpm agitation and 5% (v/v) inoculation. These findings demonstrate the feasibility of utilizing palm fronds as a renewable feedstock for the sustainable synthesis of high-value biochemicals, promoting waste valorization, and contributing to the advancement of a circular bioeconomy. Full article