Search Results (259)

Biomass gasification, a key waste-to-energy technology, is a complex thermochemical process with many input variables influencing the yield and quality of syngas. In this study, data-driven machine learning models are developed to capture the nonlinear relationships between feedstock properties, operating conditions, and syngas composition, in order to optimize process performance. Random Forest (RF), CatBoost (Categorical Boosting), and an Artificial Neural Network (ANN) were trained to predict key syngas outputs (syngas composition and syngas yield) from process inputs. The best-performing model (ANN) was then integrated into a multi-objective optimization framework using the open-source Optimization & Machine Learning Toolkit (OMLT) in Pyomo. An optimization problem was formulated with two objectives—maximizing the hydrogen-to-carbon monoxide (H₂/CO) ratio and maximizing the syngas yield simultaneously, subject to operational constraints. The trade-off between these competing objectives was resolved by generating a Pareto frontier, which identifies optimal operating points for different priority weightings of syngas quality vs. quantity. To interpret the ML models and validate domain knowledge, SHapley Additive exPlanations (SHAP) were applied, revealing that parameters such as equivalence ratio, steam-to-biomass ratio, feedstock lower heating value, and fixed carbon content significantly influence syngas outputs. Our results highlight a clear trade-off between maximizing hydrogen content and total gas yield and pinpoint optimal conditions for balancing this trade-off. This integrated approach, combining advanced ML predictions, explainability, and rigorous multi-objective optimization, is novel for biomass gasification and provides actionable insights to improve syngas production efficiency, demonstrating the value of data-driven optimization in sustainable waste-to-energy conversion processes. Full article

Solar biomass gasification results in reducing CO₂ emissions while saving biomass resources and producing higher-quality syngas when compared with conventional autothermal processes that require partial feedstock combustion for supplying the process heat. However, the solar process suffers from inherent barriers related to the variability of solar energy caused by cloud passages and shutdowns at night. The concept of hybrid solar gasification thus appears attractive for continuous and stabilized operation under intermittent or variable solar irradiation. This study addresses the dynamic simulation and control of hybrid solar–autothermal biomass gasification for continuous and stabilized syngas fuel production. A hybridization path with a constant H₂ + CO production was retained, and this control strategy was implemented in a second-by-second dynamic optimization problem using a model predictive control (MPC) algorithm. Its feasibility was demonstrated both at the small scale and industrial scale, and daily to yearly performance results were provided. For a 10 MW hybrid gasifier, the yearly solar heat share was 22% for a controlled 1000 NL/s production rate of H₂ + CO (corresponding to the complete allothermal gasification of ~2 t/h of wood at 1200 K), and this decreased with increasing H₂ + CO production objectives (17.4% at 1300 NL/s). A total of 24,200 t of wood feedstock and 8290 t of O₂ were required annually to generate 1410 t of H₂ and 19,200 t of CO, with a 1.03 average H₂:CO molar ratio. In addition, solar-only gasification and hybridization with external heating were also assessed. External auxiliary heating might be as efficient as in situ oxy-combustion and would not affect syngas composition by contamination from combustion products throughout hybridization. However, similar to external heat storage, the related thermal efficiency and heat losses must be considered. Full article

Syngas, a renewable fuel primarily composed of hydrogen and carbon monoxide, is emerging as a viable alternative to conventional fossil fuels in internal combustion engines (ICEs). Obtained mainly through the gasification of biomass and organic waste, syngas offers significant environmental benefits but also presents challenges due to its lower heating value and variable composition. This review establishes recent advances in understanding syngas combustion, chemical kinetics, and practical applications in spark-ignition (SI) and compression-ignition (CI) engines. Variability in syngas composition, dependent on feedstock and gasification conditions, strongly influences ignition behavior, flame stability, and emissions, demanding detailed kinetic models and adaptive engine control strategies. In SI engines, syngas can replace up to 100% of conventional fuel, typically at 20–30% reduced power output. CI engines generally require a pilot fuel representing 10–20% of total energy to start combustion, favoring dual-fuel (DF) operation for efficiency and emissions control. This work underlines the need to integrate advanced modelling approaches with experimental insights to optimize performance and meet emission targets. By addressing challenges of fuel variability and engine adaptation, syngas reveals promising potential as a clean fuel for future sustainable power generation and transport applications. 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

Microplastics (MPs) are an increasingly significant environmental problem, and there is growing interest in their potential as an energy source. Current investigations in this area are scarce and heterogeneous, which hinders a comprehensive assessment of both technological feasibility and implementation prospects. The aim of this paper is to provide a comprehensive review of current research on energy recovery from MPs, with particular emphasis on technologies such as pyrolysis, gasification, electrochemical methods, and hybrid biomass-based technologies. The processes were analyzed in terms of energy balance, carbon conversion, composition and energy value of the products, energy losses and by-products, reaction time and process efficiency, as well as technological complexity and scalability. Within the reviewed methodologies, pyrolysis is the most scalable method, producing valuable oils and gases efficiently. Gasification can yield hydrogen-rich syngas but is still at pilot scale. Hybrid approaches improve efficiency but need feedstock optimization, while photodegradation and electrochemical methods remain at the research stage. Further progress requires method standardization, environmental and economic assessment, and integration with existing infrastructure. Full article

The management of solid waste and the supply of energy are two of the most important environmental problems of our time. Projections indicate that by 2050, the global demand for electrical energy is expected to increase by 35% and the amount of solid waste generated to increase by 45%. In this context, polymeric waste materials such as biomass and plastics can be valorised through thermochemical processes for the generation of energy. Gasification, which converts carbonaceous materials into syngas, tar, and char, is one of the most promising recycling technologies. The composition and relative quantities of the products are influenced by the process configuration, operating parameters, and the type of fuel used. Tar removal is facilitated by adding specific catalysts to the process. The co-processing of biomass and plastics in the gasification process, called co-gasification, improves the gas yield and reduces solid residues. This review evaluates catalytic and non-catalytic co-gasification of biomass waste and non-biodegradable plastics, with a focus on syngas production and its energy potential. Full article

The utilization of biomass as a renewable energy source has the potential to play a role in mitigating climate change. Furthermore, biomass gasification represents a sustainable solution for the management of lignocellulosic waste. Topics related to the different types of gasification reactors, biomass, and economic feasibility, along with tar formation and its removal in the product gas, are discussed as general aspects in the gasification. A detailed analysis of capital and operational expenditures, the net present value, the payback period, and the internal rate of return of downdraft gasifiers has been conducted. A bibliometric analysis has been conducted; the results are presented in the form of visual maps based on keywords, and likely future trends in gasification modeling were identified. Since modeling is crucial to optimize the production or quality of the syngas, this paper discloses some important aspects related to biomass gasification carried out on downdraft gasifiers. The modeling section encompasses a range of approaches, including those based on chemical equilibrium, both stoichiometric and non-stoichiometric, kinetic models, and computational fluid dynamics. A substantial section is devoted to the modeling of the downdraft reactor, incorporating the primary conservation equations for mass, energy, and momentum. The modeling framework aims to provide a comprehensive overview for researchers seeking to simulate downdraft gasifiers. This enables researchers to utilize a summary of equations and conditions that are pertinent to their own modeling and simulations. Full article

Municipal sewage sludge (S.S.) and abundant olive-tree pruning on Lesvos Island present both a disposal challenge and an untapped energy resource. This study proposes and evaluates on a preliminary level an integrated system that utilizes both sewage sludge and pruning. The integrated system converts sewage sludge into Hydrochar (HC) via Hydrothermal Carbonization (HTC), removes the aqueous phase using passive solar distillation, and co-gasifies the dried HC with olive pruning in an autothermal downdraft gasifier. HTC experiments on anaerobically digested sludge produced HC with higher heating values exceeding 20 MJ kg⁻¹ while reducing the chemical oxygen demand of the process liquor. Gasification modelling, using the MAGSY equilibrium model, demonstrated that replacing up to 50% of lignocellulosic biomass with HC increased hydrogen content and the Lower Heating Value (LHV) of syngas. Mass and energy balances suggest that the system could provide approximately 590 kW of continuous power, contributing around 4720 MWh to the island’s annual electricity generation. These results indicate that combining HTC, solar distillation, and co-gasification offers a viable pathway to close waste loops, reduce landfill needs, and deliver renewable energy. Future work will focus on Aspen Plus design and optimization, along with a life-cycle assessment in order to assess the environmental benefits. Full article

Decarbonizing air transport is a major challenge in the global energy transition since electrification is not yet feasible. Sustainable aviation fuel (SAF) is a promising solution because it can reduce CO₂ emissions without major infrastructure changes. This study proposes a decentralized model for producing SAF in Spain through the gasification of residual lignocellulosic biomass followed by a refinement process using Fischer–Tropsch (FT) synthesis. The model uses underexploited agricultural residues such as cereal straw, vine pruning, and olive pruning, converting them into syngas in medium-scale facilities situated near biomass sources. The syngas is then transported to a central upgrading unit to produce SAF compliant with ASTM D7566 standards. The following two configurations were evaluated: one with a single gasification plant and upgrading unit and another with three gasification plants supplying one central FT facility. Energy yields, capital and operational expenditures (CAPEX and OPEX), logistic costs, and the levelized cost of fuel (LCOF) were assessed. Under a conservative scenario using one-third of the available certain types of biomass from three regions of Spain, annual SAF production could reach 517.6 million liters, with unit costs ranging from 1.63 to 1.24 EUR/L and up to 47,060 tonnes of CO₂ emissions avoided per year. The findings support the model’s technical and economic viability and its alignment with circular economy principles and climate policy goals. This approach offers a scalable and replicable pathway for decarbonizing the aviation sector using local renewable resources. Full article

Solar gasification is a thermochemical process that relies on concentrated solar radiation to heat steam and biomass to produce syngas. This study uses Machine Learning to model solar gasification using steam as an oxidizer, incorporating both thermodynamic simulations and predictive algorithms, developed using Python (version 3.11.13) scripting, to understand the relationship between the input and output variables. Three models—Artificial Neural Networks, Support Vector Machines, and Random Forests—were trained using datasets including biomass composition, solar irradiance (considering a solar furnace), and steam-to-biomass ratios in a downdraft or fluidized bed gasifier. Among the models, Random Forests provided the highest accuracy (average R² = 0.942, Mean Absolute Error = 0.086, and Root Mean Square Error = 0.951) and were used for feature importance analysis. Results indicate that radiative heat transfer and steam-to-biomass ratio are the parameters that result in the largest increase in the syngas heating value and decrease in the tar contents. In terms of composition, the hydrogen contents have a direct relationship with the H₂ and tar formed, while the carbon content affects the carbon conversion efficiency. This work highlights the of feature importance analysis to improve the design and operation of solar-driven gasification systems. Full article

This work focuses on the fabrication, characterization, and performance of a structured iron catalyst to produce hydrocarbons by the Fischer–Tropsch synthesis (FTS). The structured catalyst enhances the heat and mass transfer and provides a larger surface area and lower pressure drop. Iron-based structured catalysts indicate more activity in lower H₂/CO ratios and improve carbon conversion as compared to other metals. These catalysts were manufactured using the sponge replication method (powder metallurgy). The performance of the structured iron catalyst was assessed in a fixed-bed reactor under industrially relevant conditions (250 °C and 20 bar). The feed gas was a synthetic syngas with a H₂/CO ratio of 1.2, simulating a bio-syngas derived from lignocellulosic biomass gasification. Notably, the best result was reached under these conditions, obtaining a CO conversion of 84.8% and a CH₄ selectivity of 10.4%, where the catalyst exhibited a superior catalytic activity and selectivity toward desired hydrocarbon products, including light olefins and long-chain paraffins. The resulting structured catalyst reached a one-pass CO conversion of 84.8% with a 10.4% selectivity to CH₄ compared to a traditionally produced catalyst, for which the conversion was 18% and the selectivity was 19%, respectively. The results indicate that the developed structured iron catalyst holds considerable potential for efficient and sustainable hydrocarbon production, mainly C10–C20 (diesel-range hydrocarbons), via Fischer–Tropsch synthesis. The catalyst’s excellent performance and improved stability and selectivity offer promising prospects for its application in commercial-scale hydrocarbon synthesis processes. Full article

In the context of advancing sustainable energy solutions, this paper provides a detailed modelling study of the process integration of biomass gasification to produce syngas and subsequent methanation for methane production. The process is assumed to take place in a circulating fluidised bed and three adiabatic fixed-bed reactors. To address the low H₂/CO ratio of syngas produced from biomass gasification using air, three pre-methanation scenarios were evaluated: water gas shift reaction (scenario 1), H₂ addition through Power-to-Gas (scenario 2), and splitting syngas into pure H₂ and CO and then recombining them in a 3:1 ratio (scenario 3). The findings reveal that each scenario presents a unique balance of efficiency, decarbonisation potential, and technological integration. Scenario 2 achieves the highest overall efficiency at 62%, highlighting the importance of integrating renewable electricity into the methane industry. Scenario 1, which incorporates WGS and CO₂ capture, offers an environmentally friendly solution with an overall efficiency of 59%. In contrast, Scenario 3, involving H₂/CO separation and recombination, achieves only 44.4% efficiency due to energy losses during separation, despite its operational simplicity. Methane yields were highest in Scenario 1, while Scenario 2 offers the most significant potential for integration with decarbonised power systems. The model was validated using published data and feedstock characteristics from experimental work and industrial projects. The results showed good agreement and supported the accuracy of the simulation in reflecting realistic biomass processing for methane production. Full article

The utilisation of agricultural residues for power generation is an opportunity to reduce fossil fuel usage and foster a sustainable circular economy in Mediterranean European regions. This can be achieved by resorting to the gasification process, which faces challenges such as optimising its operation parameters on real-world applications and lowering operational costs. This work studies the gasification process of a set of agricultural biomasses widely available in the Mediterranean Europe regions through modelling and simulation in Aspen Plus. The selected biomasses are olive stone, grapevine waste, and wheat straw. The effect of temperature, equivalence ratio, and steam-to-biomass ratio on gasifier performance and their effect on gas composition was assessed. The results indicate that olive stone and wheat straw performed best in terms of syngas composition and cold gas efficiency. The analyses show good gasification performance for temperatures above 750 °C, equivalence ratios ranging from 0.1 to 0.3, depending on the raw material and steam-to-biomass ratios below 0.1. The obtained values show the validity and the potential of a downdraft gasification reactor to be used with these abundant agricultural biomasses in the Mediterranean European region. Its integration with a reciprocating engine is a rational choice for distributed power generation. 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

The biomass-to-liquid process is a promising alternative for sustainably meeting the growing demand for liquid fuels. This study focuses on the fabrication, characterization, and performance of a structured iron catalyst for producing hydrocarbons through Fischer–Tropsch synthesis (FTS). The catalyst was designed to address some drawbacks of conventional supported catalysts, such as low utilization, poor activity, and instability. The experimental investigation involved the manufacturing and characterization of both promoted and unpromoted iron-based catalysts. The performance of the structured iron catalyst was assessed in a fixed-bed reactor under relevant industrial conditions. Notably, the best results were achieved with a syngas ratio typical of the gasification of lignocellulosic biomass, where the catalyst exhibited superior catalytic activity and selectivity toward desired hydrocarbon products, including light olefins and long-chain paraffins. The resulting structured catalyst achieved up to 95% CO conversion in a single pass with 5% selectivity for CH₄. The results indicate that the developed structured iron catalyst has considerable potential for efficient and sustainable hydrocarbon production via the Fischer–Tropsch synthesis. The catalyst’s performance, enhanced stability, and selectivity present promising opportunities for its application in large-scale hydrocarbon synthesis processes. Full article