Search Results (1,680)

Rising global municipal solid waste (MSW) generation poses severe environmental and resource challenges, necessitating sustainable management strategies beyond landfilling. This review critically synthesizes thermochemical waste-to-energy (WtE) technologies, including incineration, pyrolysis, gasification, and hydrothermal carbonization, as viable pathways for converting heterogeneous MSW into energy (electricity, heat, syngas, bio-oil) and valuable materials (biochar, ash for construction). Drawing on recent literature, it highlights their superior greenhouse gas reductions, energy recovery efficiencies, and residue valorization potential compared to traditional disposal, while addressing persistent limitations such as feedstock variability, tar formation, high capital costs, and stringent emission controls. Advanced variants and integration with circular economy principles enhance feasibility, particularly in diverse regional contexts. Despite technical and economic barriers, thermochemical WtE offers a transformative approach to resource-efficient waste management, supporting zero-waste goals and renewable energy transitions when combined with optimized pre-treatment, policy incentives, and ongoing innovation in process efficiency and pollutant mitigation. Full article

This study investigates the gasification of pistachio shells for the co-production of biochar and renewable energy, integrating process simulation, energy recovery, and techno-economic–environmental assessment. The investigation has been carried out by experimental tests in a 30 kg/h downdraft gasification–cogeneration system and process simulation. The zero-dimensional simulation model, validated against first-hand experimental data, was used to evaluate two operational scenarios differing in biochar yield (10% and 17%) and energy yield. The integration of the gasification–CHP system with a representative pistachio-processing facility (500 t yr⁻¹ shell availability) demonstrated annual useful energy outputs ranging from 574 to 900 MWh yr⁻¹ (as the sum of heat and electricity). The techno-economic analysis yielded operating profits of 96,720–117,637 € yr⁻¹, return on investment (ROI) between 15.5% yr⁻¹ and 18.85% yr⁻¹, and payback periods of 6.45 and 5.3 years for the high- and low-char scenarios, respectively. The environmental assessment revealed total CO₂-equivalent savings of 241–279 t yr⁻¹, with biochar sequestration contributing up to 41% of avoided emissions. Overall, the results confirm that higher carbon conversion to syngas enhances energy, environmental and economic performance, while higher biochar yields favour fixing carbon in the soil, according to the assumed scenarios’ conditions. The proposed framework demonstrates a scalable, sustainable solution for coupling pistachio-shell gasification with industrial energy and a material valorization pathway. Full article

Linear α-olefins (LAOs) from CO/H₂ represent an attractive non-petroleum route, yet their selective formation over Fe catalysts is often limited by CO₂ formation via water–gas shift (WGS) reaction and by secondary hydrogenation that consumes terminal olefins. In this work, we demonstrate that these competing pathways can be regulated on carbon-nanotube (CNT) supported Fe catalysts by controlling the CNT interfacial oxygen environment through NO treatment or high-temperature annealing and by adjusting the Mn incorporation protocol between co-impregnation and stepwise addition. Under identical reaction conditions at 280 °C and 3.0 MPa with an H₂-to-CO ratio of 1, high-temperature treated CNTs improve olefin preservation and LAO retention compared with NO-treated CNTs. Mn promotion further shifts selectivity toward α-olefins and lowers CO₂ selectivity. At the same Fe-to-Mn ratio, the Mn introduction sequence produces distinct reducibility and CO-binding behaviors that lead to different steady-state oxide and carbide phases. XPS, H₂-TPR, and CO-TPD collectively suggest that CNT pretreatment and the Mn protocol modulate near-surface oxygen speciation, reduction kinetics, and CO adsorption strength. Mössbauer spectroscopy confirms a predominantly χ-Fe₅C₂ population and indicates the presence of ε-Fe₂C in selected samples together with residual oxide and superparamagnetic Fe species. These results highlight the importance of controlling the CNT–metal interface and Mn–Fe proximity to enhance LAO retention under high-temperature CO hydrogenation. Full article

The influence of phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH) impregnation on the pyrolysis and CO₂ gasification behavior of dairy manure was evaluated using thermogravimetric analysis (TGA), with kinetic parameters assessed through iso-conversional kinetic analysis (Frieman method). H₃PO₄ pretreatment altered early decomposition by partially removing hemicellulose and promoting the formation of thermally stable, condensed char structures. The resulting chars exhibited reduced CO₂ reactivity, as evidenced by higher gasification temperatures, lower syngas yields, and elevated activation energies, indicating hindered CO₂ diffusion and slower Boudouard reaction kinetics. In contrast, NaOH pretreatment caused only minor changes in both pyrolysis and gasification behavior. A slight reduction in pyrolysis activation energy suggested Na⁺ catalyzed bond-cleavage reactions; however, this effect did not enhance CO₂ gasification reactivity. Chars produced from NaOH-treated manure exhibited slightly higher activation energies during CO₂ gasification and syngas yields, which remained close to or slightly above those of raw manure, attributed to complex mineral interactions that diminish the catalytic influence of sodium. Overall, these findings clarify how acid and base chemical pretreatments govern char evolution and carbon-CO₂ reactivity, providing a foundation for optimizing pretreatment strategies and reactor conditions for manure conversion in CO₂-based pyrolysis and gasification systems. Full article

Waste biomass represents both an environmental pollutant and a potential renewable energy source. This study examines the feasibility of hydrogen production from tea residue biomass and solid waste, focusing on pyrolysis-based hydrogen generation. Compared to atmospheric pyrolysis, vacuum conditions reduce the saturated vapor pressure of biomass volatiles, thereby promoting char gasification, gas-phase interactions, and secondary tar cracking. Utilizing a self-designed vacuum-pyrolysis-catalysis system, we investigated the effects of key parameters—vacuum level, temperature, catalyst-to-feedstock ratio, and retention time on pyrolysis product distribution and formation mechanisms. Results indicate that Ni was successfully and uniformly loaded onto waste calcium oxide desiccant (DC) support via impregnation, thereby significantly increasing the specific surface area of the catalyst. Optimization using response surface methodology identified the following optimal conditions: pressure of 5 kPa, temperature of 835.89 °C, catalyst/feedstock ratio of 110.02%, and retention time of 2.35 h. Under these conditions, a hydrogen yield of 256.39 mL·g⁻¹ was achieved, corresponding to 95.3% of the simulated value. The process not only enabled efficient hydrogen production but also simultaneously yielded bio-oil and biochar, thereby facilitating carbon capture and recycling. These findings provide valuable insights into the resource-oriented application of vacuum pyrolysis-catalysis technology to waste biomass. Full article

With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), zinc slag, lithium slag (LS), electrolytic manganese residue (EMR), phosphogypsum (PG), water treatment sludge (WTS), sewage sludge, blast furnace slag (BFS), steel slag (SS), coal fly ash (CFA), coal gasification slag (CGS), copper smelting slag (CSS), and lead smelting slag (LSS). Having been chemically processed, they exhibit complex compositions that pose challenges for further utilization. In this paper, we comprehensively review the preparation of adsorbents from IISWs as raw materials, the applications of IISW-derived adsorbents, and their adsorption mechanisms. The obtained adsorbents include modified IISWs, zeolites, porous ceramics, and composite and hybrid adsorbents. The adsorption mechanisms, such as van der Waals forces, electrostatic interactions, and π–π interactions, contribute to the rapid adsorption kinetics and high adsorption capacity observed in these adsorbents. Full article

Synthetic natural gas (SNG) production from biomass residues represents a promising strategy to reduce greenhouse gas emissions and enhance energy security in regions with abundant agricultural waste. This study evaluates the thermodynamic performance of SNG synthesis from rice husk (RH) and empty fruit bunches (EFB) bio-oils, major residues in the department of Bolívar, Colombia. The process was simulated in Aspen Plus^®, integrating syngas data and methanation under equilibrium conditions at 320 °C and 30 bar, complemented by hydrogen injection via alkaline electrolysis to maintain an H₂/CO ratio above 3. Energy and exergy analyses were performed to quantify efficiencies and irreversibilities. Results indicate carbon conversion rates of 48.3% for EFB and 47.4% for RH, producing SNG with 96% CH₄ suitable for grid injection. Energy efficiencies reached 71.9% and 71.0%, while exergy efficiencies were 87.2% and 82.9%, respectively, aligning with or surpassing literature benchmarks. The main irreversibilities occurred in methanation and CO₂ removal, highlighting thermal integration and gas recycling as key improvement strategies. These findings demonstrate the potential of leveraging local biomass for clean energy production and support the development of Power-to-Gas systems in Colombia. Full article

The aqueous phase (AP) produced during hydrothermal liquefaction (HTL) contains high organic loads and a chemically complex mixture of dissolved intermediates, posing significant environmental management challenges. Aqueous phase recycling (APR) has emerged as a strategy to enhance bio-crude yield, improve energy recovery, and reduce freshwater consumption by reintroducing reactive water-soluble species into subsequent cycles. However, repeated recycling can lead to the accumulation of N-containing compounds and phenolics, potentially diminishing bio-crude quality and heating value through secondary polymerization and condensation reactions. Simultaneously, the carbon and nutrient-rich character of AP presents opportunities for valorization via anaerobic digestion, microalgae cultivation, and supercritical water gasification. Despite growing interest, APR-HTL research remains feedstock-specific, and a systematic understanding of AP compositional evolution across multiple recycling cycles is limited. This review synthesizes recent progress, highlighting mechanistic linkages between AP composition, bio-crude performance, and integrated biorefinery strategies. Full article

Despite global efforts to reduce landfill use for municipal waste, many sites remain active, and older closed sites still require management, particularly regarding leachate. Landfill leachate contains varying levels of organic and inorganic pollutants, generated through biological and physicochemical processes following water infiltration. Its complex composition—including COD, inorganic macro-components, heavy metals, and xenobiotics—necessitates effective treatment technologies to enable safe discharge into surface waters. This study compares low-cost, eco-sustainable adsorbents for the removal of ammonium, trace elements (Cd, Be, Fe, Cu, Ni, Pb, Cr, As, Sn, Sb, Se), and color (as an indirect measure of organic compounds) from urban landfill leachate. In more detail, six biochars from different biomass feedstocks and pyro-gasification conditions as well as natural chabazite and synthetic zeolite 13X (FAU-type) were investigated. After characterization, biochars were characterized and adsorption performance was assessed. Removal performance was comparatively evaluated after 24 h batch contact under fixed experimental conditions. Results showed that gasified biochars achieved high removal efficiency for metals and color but were ineffective for ammonium. Instead, both zeolites demonstrated efficient ammonium removal (~50%) but were less efficient for metals, reflecting the mechanism-driven selectivity of the adsorbents studied. Finally, a principal component analysis (PCA) revealed correlations between biochar physicochemical properties and contaminant retention, providing insight into key factors governing adsorption and informing the design of sustainable leachate treatment strategies. Full article

An experiment was conducted to produce synthesis gas (main components CO and H₂) via plasma–steam gasification of brown coal with an ash content of 9% and a volatile matter yield of 48%. Satisfactory agreement between the calculation results and experiments for various types of solid fuel allowed the TERRA thermodynamic calculation program to be verified. A thermodynamic analysis of plasma–steam gasification of shale, brown, and hard coals was performed over a wide range of their characteristics (ash content 3–88%, volatile yield 5–50%) at temperatures from 600 to 3000 K. The composition of the gas and condensed phases of the gasification products, the degree of carbon gasification, and the specific energy consumption for the process were calculated. Although solid fuels differ significantly in ash content and volatile matter yield, synthesis gas is the primary gaseous product of their gasification, with a higher hydrogen concentration than carbon monoxide, thereby improving the environmental performance of solid fuels. In all types of fuels, the maximum synthesis gas concentration occurs between 1200 and 1600 K, with low ballast impurities (H₂O, CO₂, N₂) and zero harmful emissions (NO_X, SO_X). Synthesis gas combustion heat ranges from 10,475 to 11,570 kJ/m³. A 100% gasification rate occurs at temperatures between 1250 and 1300 K. Energy consumption varies between 0.7 and 2.7 kWh/kg. In solid fuel plasma–steam gasification, the volatile yield reduces specific energy consumption, but the ash content has a negligible effect. Plasma–steam gasification of solid fuels containing 9 and 88% ash and 48% and 50% volatile yield shows a 12% reduction in specific energy consumption. Plasma–steam gasification of solid fuels with volatile yields of 48 and 5% and ash contents of 9% and 3%, respectively, results in a 60% reduction in specific energy consumption. Full article

This study provides a comprehensive evaluation of waste-to-energy (WtE) technologies in Saudi Arabia, focusing on municipal solid waste (MSW) across various cities, in alignment with Saudi Vision 2030. Saudi Arabia generates approximately 16 million tons of MSW annually, primarily composed of organic matter (37–57%), followed by paper (11–28%) and plastics (5–36%). According to Vision 2030 projections, MSW generation is expected to increase to approximately 30 million tons per year by 2033, driven by population growth, urbanization, and increased tourism activities. Waste quantities notably increase during the Hajj and Ramadan seasons. The study assesses three main WTE technologies: biochemical, chemical, and thermochemical processes. Anaerobic digestion (AD) effectively converts organic waste into biogas with a methane content of 60% to 80%, potentially yielding up to 2.99 TWh annually. Transesterification efficiently targets fats in waste, generating around 244.2 GWh per year. Thermochemical processes, including incineration, gasification, and pyrolysis, are suitable for high-calorific waste. Incineration can significantly reduce waste volume and generate up to 2073 MW while lowering GHG emissions. Economic assessments reveal that biochemical methods are the most cost-effective for managing organic waste, while thermochemical methods, despite higher capital costs, achieve significant energy recovery. Integrating WTE technologies with recycling is crucial for enhancing environmental sustainability and supporting Saudi Arabia’s Vision 2030 objectives. Full article

Thermochemical conversion of plastic waste to hydrogen and synthesis gas represents a potential pathway for energy recovery from heterogeneous waste streams. The feasibility and performance of such systems are fundamentally governed by thermodynamic constraints and heat-management requirements. This review critically examines the thermodynamic and heat-integration aspects of plastic waste conversion to hydrogen and syngas, with emphasis on pyrolysis, steam reforming, gasification, and system-level behaviour. Key thermodynamic features of plastic pyrolysis, reforming, and gasification are discussed, including reaction endothermicity, equilibrium limitations, temperature effects, and product distribution trends. The role of steam reforming and water–gas shift reactions in enhancing hydrogen yield is assessed from equilibrium and energy-demand perspectives. Heat integration emerges as a critical determinant of overall efficiency, with recoverable waste heat present at multiple process stages offering opportunities for internal heat recovery. Energy and exergy analyses identify dominant sources of irreversibility and enable comparison of plastic-derived hydrogen systems with conventional thermochemical hydrogen production routes. Quantitatively, conventional steam methane reforming achieves energy efficiencies of 65–75% and exergy efficiencies of 60–70%, whilst plastic-derived systems without extensive heat integration report 45–60% and 40–55%, respectively. Key challenges include limited thermodynamic property data for real plastic-derived mixtures, insufficient reconciliation of equilibrium and kinetic behaviour, incomplete system-level heat-integration analysis, and scarcity of comprehensive exergy-based evaluations. This review provides a thermodynamic framework for assessing the opportunities and limitations of hydrogen production from plastic waste. Full article

Coastal regions concentrate livestock and fisheries activities that generate large volumes of organic residues, often managed inadequately and contributing to nutrient loading, soil degradation, and marine pollution. At the same time, these territories face increasing pressure to decarbonise energy systems and restore degraded soils under climate change. This article proposes an integrated conceptual framework for the valorisation of livestock and fisheries residues through hydrogen-centred energy recovery and biochar-based soil regeneration, with a focus on coastal regions of Colombia. The framework integrates biological and thermochemical conversion pathways, including anaerobic digestion, fermentation, gasification, and pyrolysis, within a unified system boundary that treats organic residues as secondary resources rather than environmental liabilities. Hydrogen is a transitional energy carrier enabling near-term decarbonisation within decentralised residue valorisation systems, while biochar is positioned as a key co-product enabling long-term carbon stabilisation and soil regeneration. By linking material and energy flows at the territorial scale and accounting for governance constraints and environmental vulnerabilities, the framework highlights the potential of decentralised residue valorisation systems. These systems can reduce coastal pollution, enhance soil resilience, and contribute to climate mitigation in fragile ecosystems. Full article

Driven by cleaner energy demands, environmental regulations, and technological advances, coal science is rapidly evolving, creating the need to understand its transition and transformation within the global energy research landscape. Building upon earlier national- and topic-specific bibliometric studies, this study presents a comprehensive long-term global bibliometric analysis of coal research (1975–2024), based on 272,370 Web of Science records, applying the Cross-Disciplinary Publication Index (CDPI), the Technology–Economic Linkage Model (TELM), VOSviewer, and Excel to assess research growth, structural shifts, and interdisciplinary integration. Results show that coal research is dominated by articles (74%) with publication output peaking at ~19,500 in 2024, reflecting fluctuations in global coal prices due to energy transition market dynamics. CDPI results highlight Energy & Fuels (0.83), Chemical Engineering (0.80), Environmental Sciences (0.77), Materials Science (0.74), and Geosciences (0.66), showing coal’s central role across technology, environment, and geological research domains and revealing a clear shift toward sustainability-oriented and advanced material applications. China leads output (122,130 publications), with strong contributions from the China University of Mining and Technology and the Chinese Academy of Sciences, while the USA, Australia, and Europe maintain strong international collaboration networks. The evolution of coal research can be divided into three major phases: conventional mining, coal preparation, combustion, and coalbed methane commercialization (1975–2004; ~64,000 publications); integrated gasification combined cycle (IGCC) and carbon capture and storage (CCS) technologies (2005–2014; ~58,707 publications); and a recent phase dominated by by-product valorization, carbon capture utilization and storage (CCUS), and digital technologies (AI, IoT, ML) (2015–2024; ~146,174 publications). Contemporary coal research spans three interconnected domains: energy supply (≈36% of global electricity generation and ~15 Gt CO₂ emissions), resource and geoscience applications (including large-scale fly ash utilization and critical element recovery), and environmental and health impacts related to greenhouse gas and pollutant emissions. The findings demonstrate that coal science is transitioning from a conventional fossil fuel-centered discipline toward an integrated, interdisciplinary energy research field, emphasizing emission reduction, resource efficiency, digitalization, and circular economy applications, thereby extending prior bibliometric studies through unprecedented temporal coverage, global scope, and the combined application of CDPI and TELM frameworks, providing critical insights for future energy strategies and policy development. Full article

Biomass chemical looping gasification coupled with CO₂ splitting (BCLGCS) presents a promising carbon-negative route for simultaneous syngas production and CO₂ utilization, where the selection of oxygen carriers (OCs) is critical. Compared to single-metal oxides, composite metal OCs offer thermodynamic advantages. This study aims to evaluate the thermodynamic performance of composite metal OCs (LaFeO₃, BaFeO₃, CaFe₂O₄, and Ca₂Fe₂O₅) in BCLGCS to overcome the thermodynamic limitations of conventional biomass-CO₂ gasification. Gibbs free energy minimization calculations were performed to predict gas compositions and oxygen carrier phase transformations under varying operating conditions. Results show that steam addition promotes gasification by increasing H₂ content and lowering required temperatures, but substantially reduces CO₂ conversion in the splitting reactor by consuming residual char. Ca₂Fe₂O₅ demonstrates superior adaptability with tunable H₂/CO ratios, while LaFeO₃ requires high OC loading and BaFeO₃ undergoes deactivation via BaCO₃ formation. This work reveals inherent thermodynamic conflicts between gasification and CO₂ splitting steps, indicating that the optima for syngas production and CO₂ utilization are mutually exclusive, an insight not previously quantified in BCLGCS literature. The findings provide theoretical guidance for designing carbon-tolerant OCs and optimizing process parameters, advancing BCLGCS toward practical carbon-negative applications. Full article