Search Results (68)

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

Due to the growing global population, rising energy demands, and the environmental impacts of fossil fuel use, there is an urgent need for sustainable energy sources. Biomass conversion technologies have emerged as a promising solution, particularly supercritical water gasification (SCWG), which enables efficient energy recovery from wet and dry biomass. This systematic review, following PRISMA 2020 guidelines, analyzed 51 peer-reviewed studies published between 2015 and 2025. The number of publications has increased over the decade, reflecting rising interest in SCWG for energy production. Research has focused on six biomass feedstock categories, with lignocellulosic and wet biomasses most widely studied. Reported energy efficiencies ranged from ~20% to >80%, strongly influenced by operating conditions and system integration. Integrating SCWG with solid oxide fuel cells, organic Rankine cycles, carbon capture and storage, or solar input enhanced both energy recovery and environmental performance. While SCWG demonstrates lower greenhouse gas emissions than conventional methods, many studies lacked comprehensive life cycle or economic analyses. Common limitations include high energy demand, modeling simplifications, and scalability challenges. These trends highlight both the potential and the barriers to advancing SCWG as a viable biomass-to-energy technology. Full article

Acrylonitrile–butadiene–styrene (ABS) has been widely used as an engineering thermoplastic, and the increasing post-consumer waste of ABS plastics calls for efficient and sustainable recycling technologies. The recent advances in ABS recycling technologies were investigated to enhance material recovery, purity, and environmental performance. Thermo-oxidative degradation compromises mechanical integrity during reprocessing, while minor reductions in molecular weight increase melt flow rates. Surface modification techniques such as boiling treatment, Fenton reaction, and microwave-assisted flotation facilitate the selective separation of ABS from mixed plastic waste by enhancing its hydrophilicity. Dissolution-based recycling using solvent and anti-solvent systems enables the recovery of high-purity ABS, though some additive losses may occur during subsequent molding. Magnetic levitation and triboelectrostatic separation provide innovative density and charge-based sorting mechanisms for multi-plastic mixtures. Thermochemical routes, including supercritical water gasification and pyrolysis, generate fuel-grade gases and oils from ABS blends. Mechanical recycling remains industrially viable when recycled ABS is blended with virgin resin, whereas plasma-assisted mechanochemistry has emerged as a promising technique to restore mechanical properties. These recycling technologies contribute to a circular plastic economy by improving efficiency, reducing environmental burden, and enabling the reuse of high-performance ABS materials. Full article

This work aims to present tes-thermo, a Python library developed to solve thermodynamic equilibrium problems using the Gibbs energy minimization approach. The library is a variant of TeS v.3, a standalone executable developed for the same purpose. The tool formulates the chemical equilibrium problem of combined phases as a nonlinear programming problem, implemented using Pyomo (Python Optimization Modeling Objects) and solved with IPOPT (Interior Point OPTimizer). To validate the tool and demonstrate its robustness, the supercritical water gasification (SCWG) of methanol and ethanol was investigated. The Peng–Robinson equation of state was employed to account for non-idealities in the gas phase. Experimental and simulated data from the literature were used for validation, and, in both cases, the results were satisfactory, with root mean square errors consistently below 0.23. The SCWG processes studied revealed that hydrogen production is favored by increasing temperature and decreasing pressure. For both methanol and ethanol, increasing the carbonaceous substrate fraction in the feed promotes hydrogen formation; however, it also leads to reduced hydrogen relative yield due to the enhanced formation of methane and carbon monoxide under these conditions. Consequently, although hydrogen production increases, the hydrogen molar fraction in the dry gas stream tends to decrease with the higher substrate content. As expected, the SCWG of methanol produces more hydrogen and less carbon monoxide compared to ethanol under similar conditions. This behavior is consistent with the higher carbon content in ethanol, which favors reactions leading to carbon oxides. In summary, tes-thermo proves to be a robust and reliable tool for conducting research and studies on topics related to thermodynamic equilibrium. Full article

Gasification of municipal solid waste and other biogenic residues (e.g., biomass and biowaste) is increasingly recognized as a promising thermochemical pathway for converting non-recyclable fractions into valuable energy carriers, with applications in electricity generation, district heating, hydrogen production, and synthetic fuels. This paper provides a comprehensive analysis of major gasification technologies, including fixed bed, fluidized bed, entrained flow, plasma, supercritical water, microwave-assisted, high-temperature steam, and rotary kiln systems. Key aspects such as feedstock compatibility, operating parameters, technology readiness level, and integration within circular economy frameworks are critically evaluated. A comparative assessment of incineration and pyrolysis highlights the environmental and energetic advantages of gasification. The valorization pathways for main product (syngas) and by-products (syngas, ash, tar, and biochar) are also explored, emphasizing their reuse in environmental, agricultural, and industrial applications. Despite progress, large-scale adoption in Europe is constrained by economic, legislative, and technical barriers. Future research should prioritize scaling emerging systems, optimizing by-product recovery, and improving integration with carbon capture and circular energy infrastructures. Supported by recent European policy frameworks, gasification is positioned to play a key role in sustainable waste-to-energy strategies, biomass valorization, and the transition to a low-emission economy. Full article

This study explores innovative strategies for decarbonizing sludge thermal treatments used in electrical power generation, with a focus on integrating sensor technologies and artificial intelligence. Sludge, a carbon-intensive byproduct of wastewater treatment, presents both environmental challenges and opportunities for energy recovery. The paper provides a comprehensive analysis of thermal processes such as pyrolysis, gasification, co-combustion, and emerging methods, including hydrothermal carbonization and supercritical water gasification. It evaluates their carbon mitigation potential, energy efficiency, and economic feasibility, emphasizing the importance of catalyst selection, carbon dioxide capture techniques, and reactor optimization. The role of real-time monitoring via sensors and predictive modeling through artificial intelligence (AI) is highlighted as critical for enhancing process control and sustainability. Case studies and recent advances are discussed to outline future pathways for integrating thermal treatment with circular economy principles. This work contributes to sustainable waste-to-energy practices, supporting global decarbonization efforts and advancing the energy transition. Full article

The production of Fischer–Tropsch liquid biofuels from the supercritical water gasification (SCWG) of lignocellulosic biomass is energetically and environmentally assessed by coupling process modelling with Life-Cycle Assessment. A conceptual process model has been developed comprising the following stages: (a) the thermochemical conversion of lignocellulosic biomass in a supercritical water gasification (SCWG) reactor, (b) syngas upgrade through dry reforming (DRR), (c) liquid biofuel production from Fischer–Tropsch synthesis (FTS) and (d) FT product upgrade and refinement, so that diesel-like (FT—Diesel), gasoline-like (FT—Gasoline), and jet fuel-like (FT Jet Fuel) yields are predicted. Parametric studies have been performed, highlighting the effect of biomass concentration and SCWG temperature on end-product yields. Furthermore, alternative scenarios have been examined with respect to: (a) maximizing FT liquid biofuel yields and (b) minimizing heat requirements to potentially achieve a thermally self-sustained process. The results of the simulated process, including liquid biofuel yield and heat-demand predictions, are used as inputs in the inventories compiled for the Life-Cycle Assessment of the overall process. Agricultural and feedstock transportation stages have also been considered. Energetic and environmental benefits and challenges are highlighted through the quantification of Global Warming Potential (GWP), while special importance is assigned to following the REDII sustainability methodology and reference data. Full article

Coasts are home to one-third of the human population. In the process of energy transition, local biomass and waste resources represent a renewable fuel that can substitute fossil fuels in order to reduce greenhouse gas emissions, hence including marine resources as part of the eligible feedstock for renewable energy production. Gasification regroups different technologies that aim to convert a solid fuel into a useful gas, and has several applications, such as heat production, power generation, and chemical synthesis. Gasification technologies regroup the traditional “dry” processes that use relatively dry fuels, but recent developments have been made with “wet” processes such as hydrothermal gasification, in sub- or supercritical conditions for the water, which can accept wet fuel. This review focuses on scientific articles that performed gasification of marine resources in order to produce a syngas. First, a definition of marine resources is made, followed by the presentation of marine resources studied in the literature. Secondly, this review presents the different types of gasification reactors and their operating conditions, followed by a summary of the different syngas produced with their composition as a performance indicator. Finally, this review exposes the limitations of the current literature and concludes with perspective propositions. Full article

Biomass is perhaps the only renewable resource on the planet capable of delivering molecules similar to those derived from petroleum, and one of the most developed technologies to achieve this is gasification. When it comes to biomass conversion into fuels and commodities, supercritical water gasification (SCWG) could offer promising solution for producing hydrogen-rich syngas. However, the presence of methane (CH₄) and carbon dioxide (CO₂) in the syngas could negatively impact downstream processes, particularly when carbon monoxide is also required. Hence, improving the quality of the syngas produced from biomass gasification is essential for promoting the sustainability of several industrial processes. In this context, understanding the principles of the dry reforming of methane (DRM) becomes essential for upgrading syngas with high CH₄ and CO₂ content, especially when the carbon monoxide content is low. In addition to the experimental conditions used in such process, it has been reported that the material composition of the reactor can impact on reforming performance. Hence, this work aims at comparing the catalytic efficacy of Inconel and stainless steel for reforming syngas derived from SCWG under standard DRM conditions. In this specific work, the metals were directly used as catalyst and results showed that when using Inconel powder, CH₄ conversion increased from 3.03% to 37.67% while CO₂ conversion went from 23.16% to 51.48% when compared to stainless steel. Elemental and structural analyses revealed that the Inconel’s superior performance might be due to its high nickel content and the formation of active oxide compounds, such as FeNiO, FeCrO₃, Fe₃O₄, Cr₂O₃, and Cr₂NiO₄, during the reaction. In contrast, Fe₃O₄ was the only oxide found in stainless steel post-reaction. Additionally, increasing the total gas feed flow rate was shown to reduce CH₄ and CO₂ conversions, supporting the known impact of residency time on catalytic efficiency. Full article

The supercritical water gasification (SCWG) and carbon dioxide gasification of agro-industrial and urban waste residues—Coffee Husk, Eucalyptus Biochar, Energy Sugarcane, and Refuse-Derived Fuel (RDF)—were studied using TeS^® v.2 software, which employs a non-stoichiometric thermodynamic model to minimize Gibbs free energy and predict equilibrium compositions. The effects of temperature (873.15–1273.15 K), pressure (220–260 bar), biomass feed (18–69%), and gasifying agents on hydrogen and methane formation were analyzed. Higher temperatures and biomass feed percentages favored hydrogen production, while lower temperatures increased methane formation. At 1273.15 K, RDF showed the highest hydrogen yield in SCWG, rising from 0.43 to 1.42 mol, followed by Energy Sugarcane (0.39 to 1.23 mol), Coffee Husk (0.34 to 0.74 mol), and Eucalyptus Biochar (0.33 to 0.62 mol). In CO₂ gasification, hydrogen yields were lower but followed a similar trend. At 873.15 K, RDF also exhibited the highest methane increase in SCWG, from 0.14 to 0.91 mol, followed by Energy Sugarcane (0.12 to 0.65 mol), Coffee Husk (0.11 to 0.36 mol), and Eucalyptus Biochar (0.11 to 0.29 mol). Methane formation in CO₂ gasification was significantly lower, with RDF increasing from 0.0035 to 0.35 mol, followed by Energy Sugarcane (0.0024 to 0.24 mol), Coffee Husk (0.0002 to 0.058 mol), and Eucalyptus Biochar (0.0002 to 0.028 mol). On the other hand, a slight increase in hydrogen formation was observed as pressure decreased, while the opposite effect was observed for methane formation, with a small increase in its production as pressure increased. The impact of pressure change on the equilibrium compositions was not as significant as the effect observed by varying temperature; this behavior was observed in both gasification processes studied. Additionally, the behavior of the H₂/CO molar ratio for each biomass in the studied gasification processes was analyzed to assess the potential uses of the produced syngas. It was observed that the SCWG resulted in significantly higher H₂/CO molar ratios compared to CO₂ gasification. Full article

This work evaluated the alterations in the levels and types of polycyclic aromatic hydrocarbons (PAHs) within both liquid and solid products throughout the process of the catalytic supercritical water gasification of dewatered sewage sludge to examine the catalytic effect of various catalysts and the inhibit reaction pathways. The addition of Ni, NaOH, Na₂CO₃, H₂O₂, and KMnO₄ reduced the concentrations of PAHs, with Ni and H₂O₂ showing the best performance. The concentrations of PAHs, especially higher-molecular-weight compounds in the residues, decreased sharply as the H₂O₂ amount increased. At a 10 wt% H₂O₂ addition, the levels of PAHs in the liquid and solid products were reduced by 91% and 88%, respectively. High-ring PAHs were not detected in the residues as the H₂O₂ amount increased to an 8 wt%. H₂O₂ addition evidently inhibits PAH formation by promoting the ring-opening reactions of initial aromatic compounds in raw sludge and inhibiting the polymerization of open-chain intermediate products. The addition of NaOH + H₂O₂ or Ni + H₂O₂ as combined catalysts significantly lowered PAH concentrations while increasing the H₂ yield. The addition of 5 wt% Ni + H₂O₂ reduced PAH concentrations in the liquid and solid residues by 70% and 44%, respectively, while the H₂ yield escalated from 0.13 mol/kg OM to 3.88 mol/kg OM. Possible mechanisms associated with the reaction pathways of these combined catalysts are proposed. Full article

Syngas, mostly hydrogen and carbon monoxide, has traditionally been produced from coal and natural gas, with biomass gasification later emerging as a renewable process. It is widely used in fuel synthesis through the Fischer–Tropsch (FT) process, where the H₂/CO ratio is crucial in determining product efficiency and quality. In this sense, this study aimed to reform an emulated syngas resulting from the supercritical water gasification of biomass, tailoring it to meet the H₂/CO ratio required for FT synthesis. Conditions resembling dry reforming were applied, using temperatures from 600 to 950 °C and steel wool as a catalyst. Additionally, the effects of Inconel and stainless steel as reactor materials on syngas reforming were investigated. When Inconel was used, H₂/CO ratios ranged between 1.04 and 1.84 with steel wool and 1.28 and 1.67 without. When comparing reactions without steel wool performed either in the Inconel or the stainless steel reactors, those using Inconel consistently outperformed the stainless steel ones, achieving CH₄ and CO₂ conversions up to 95% and 76%, respectively, versus 0% and 39% with stainless steel. It was concluded that the Inconel reactor exhibited catalytic properties due to its high nickel content and specific oxides. Full article

Supercritical multicomponent thermal fluid (scMCTF) is a novel medium with great potential for heavy oil thermal recovery. The production rate of scMCTF will affect the injection efficiency of thermal fluid, and then affect the development effect of thermal recovery. However, at present, there are few reports on the production rate of each component of scMCTF, and their understanding is not clear. According to the existing production rate data of supercritical water (scH₂O) gasification products, based on the generation mechanism of scMCTF, the production rate of thermal fluid generation products under different generation conditions was calculated, and its influencing factors were identified. The results show the following: (1) The factors affecting the production rate of scMCTF generation products can be divided into three categories: reaction raw material factors, reaction condition factors, and catalytic factors. (2) The hydrocarbon number of raw material, reaction temperature, reaction time, and catalyst concentration were positively correlated with the production rate of the product. (3) The concentration of the reaction raw material is negatively correlated with the production rate of the product. The higher the concentration of the raw material is, the lower the concentration of H₂O is, and the steam reforming reaction is inhibited, which leads to the decrease in the production rate. (4) The effect of reaction pressure and catalyst load on the product is not significant. (5) The reaction product production rate increased first and then decreased with the ratio of H₂O to oil in the raw material emulsion and the ratio of preheated H₂O to raw material discharge. (6) The effect of metal salt catalysts is relatively stable, and the catalytic effect of simple metal catalysts is significantly different under the action of different types of accelerators, so it is necessary to study the degree of synergization of different accelerators on the catalytic effect. The results can lay a foundation for the subsequent experimental and theoretical research design. Full article

The increasing amount of sewage sludge produced demands new methods of its management to minimize socioeconomic and environmental problems related to its current treatment. An effective solution may be the thermochemical conversion of sewage sludge through gasification. First, the most known sewage sludge gasification processes are presented along with the challenges that they face. Then the detailed characteristics of sewage sludge are discussed from the point of view of its use in the gasification process, as well as research on the kinetics of gasification of sewage sludge char using various models. As scientific reports on sewage sludge gasification focus on the influence of process parameters on gas yield and composition (especially H₂ and tar content), the main part of the work is devoted to the discussion on the influence of temperature, type, and amount of the gasifying agent and the presence of a catalyst on these parameters. Moreover, the co-gasification of sewage sludge as well as advanced gasification methods, i.e., supercritical water gasification and plasma gasification, are analyzed. Finally, the possibilities of utilization of sewage sludge gasification process by-products were discussed and the impact of the process on the environment was assessed. The review concludes with indications of directions for further research. Full article

This study introduces a novel hybrid solar–biomass cogeneration power plant that efficiently produces heat, electricity, carbon dioxide, and hydrogen using concentrated solar power and syngas from cotton stalk biomass. Detailed exergy-based thermodynamic, economic, and environmental analyses demonstrate that the optimized system achieves an exergy efficiency of 48.67% and an exergoeconomic factor of 80.65% and produces 51.5 MW of electricity, 23.3 MW of heat, and 8334.4 kg/h of hydrogen from 87,156.4 kg/h of biomass. The study explores four scenarios for green hydrogen production pathways, including chemical looping reforming and supercritical water gasification, highlighting significant improvements in levelized costs and the environmental impact compared with other solar-based hybrid systems. Systems 2 and 3 exhibit superior performance, with levelized costs of electricity (LCOE) of 49.2 USD/MWh and 55.4 USD/MWh and levelized costs of hydrogen (LCOH) of between 10.7 and 19.5 USD/MWh. The exergoenvironmental impact factor ranges from 66.2% to 73.9%, with an environmental impact rate of 5.4–7.1 Pts/MWh. Despite high irreversibility challenges, the integration of solar energy significantly enhances the system’s exergoeconomic and exergoenvironmental performance, making it a promising alternative as fossil fuel reserves decline. To improve competitiveness, addressing process efficiency and cost reduction in solar concentrators and receivers is crucial. Full article