Search Results (665)

This study reports on the design, construction, and operation of a laboratory-scale biomass gasification reactor, together with the procedures used to define and evaluate key operational and performance variables, including piston velocity, nominal biomass residence time, airflow rate, gas yield, lower heating value, and gasification efficiency. The unit is a moving-bed reactor operating in co-current gas–solid mode and reproducing key features of downdraft-like gasification, allowing the identification of the four main reaction zones: drying, pyrolysis, oxidation, and reduction. The reactor exhibits simple operation and handling and, notably, enables controlled axial displacement of the biomass bed through the reaction zone, allowing the nominal solid residence time in the heated zone to be adjusted through piston motion. In addition, the gasification of Spartina argentinensis was investigated in order to evaluate the functionality of the system and to assess reactor performance under selected operating conditions. At operating temperatures of 800–850 °C and an equivalence ratio of 0.2, gas yields exceeded 60 wt%, gasification efficiencies were above 50%, and the product gas reached heating values close to 1000 kcal Nm⁻³, indicating a favorable fuel quality of the product gas. These results confirm the potential of the proposed reactor as a useful experimental platform for the investigation of biomass gasification under controlled laboratory conditions. Full article

Syngas (synthesis gas) is a promising gaseous biofuel for small-scale power generation, but its highly variable composition, which depends on the biomass source and gasification process, poses challenges for engine optimization. This study investigates syngas–diesel dual-fuel combustion in an optically accessible engine using chemiluminescence imaging of OH*, CH*, and CH₂O* to characterize ignition and flame development. Three representative syngas compositions—Downdraft, Updraft, and Fluidbed—were examined. The Fluidbed composition exhibited the weakest OH* signal, approximately one-third of that observed for the other two, primarily due to its higher CO₂ dilution and lower H₂ content. Ignition delay trends were strongly correlated with dilution level: Downdraft and Updraft showed similar delays despite different H₂/CO ratios, while larger CO₂ shares led to longer delays and flattened heat-release rates. CH* and CH₂O* chemiluminescence showed better agreement with combustion timing than OH*. Methane enrichment enhanced flame propagation and reduced ignition delay, partially offsetting CO₂ dilution effects. Full article

The rational design of oxygen carriers (OCs) is critical for enhancing biomass chemical looping gasification (BCLG) performance. This work systematically investigated the effects of different supports (Al₂O₃, ZrO₂, TiO₂, SiO₂) on the performance of NiFe-based OCs with oxidation and catalytic reforming functions. The gasification reactivity and support-active phase interaction of OCs in both oxidized and reduced states were evaluated. XRD, H₂-TPR, XPS, and SEM techniques were employed to characterize the phase composition, synergistic interactions, and surface morphology. The results showed that NiFeAl exhibited the optimal gasification performance in both oxidized and reduced states, achieving a syngas (H₂ + CO) yield of approximately 1.4 m³/kg (dry walnut shell). NiFeAl featured a higher Fe binding energy, abundant cavity structures, and the uniform dispersion of Ni and Fe on Al₂O₃, which confirm the formation of an appropriately strong Ni-Fe-Al ternary system. In contrast, NiFeZr suffered from the higher CO₂ yield, attributed to the over-oxidation caused by the weak interactions. NiFeTi and NiFeSi had lower syngas yields due to their poor reducibility induced by excessively strong interactions. This work verifies that moderate support-active phase interactions in OCs are optimal for BCLG. Full article

Biomass pyrolysis has emerged as a flexible platform for converting low-value residues into higher-value energy carriers (bio-oil, biochar and gas) and carbon-rich materials, with realistic potential for negative emissions when biochar is deployed in long-lived sinks. Over the last decade, three developments have driven the field forward: first, a finer mechanistic understanding of devolatilization and secondary reactions; second, major improvements in analytical techniques for characterising feedstocks and products; and third, more rigorous techno-economic and life-cycle assessments that place pyrolysis in a broader energy-system context. Recent experimental work on forestry and agro-industrial residues has clarified how biomass composition, ash chemistry and operating conditions jointly govern product yields, energy content and stability. Parallel advances in GC×GC–MS, high-resolution mass spectrometry, NMR and thermogravimetric methods have shifted the discussion from bulk “bio-oil” and “char” to families of molecules and well-defined structural domains, which can be deliberately targeted by reactor and catalyst design. Data-driven models, ranging from support vector machines applied to TGA curves to ANFIS and random forests for yield prediction, are now accurate enough to support process screening and multi-objective optimisation. At the system level, commercial fast pyrolysis biorefineries report overall useful energy efficiencies on the order of 80–86%, while slow pyrolysis configurations centred on biochar can be economically viable when carbon storage and co-products are appropriately valued. Thermodynamic analyses confirm that indirect gasification via fast-pyrolysis oil sacrifices some energy and exergy efficiency relative to direct solid-biomass gasification but may offer logistical and integration advantages. This review synthesises recent work on (i) feedstock and process characterisation; (ii) state-of-the-art analytical methods for bio-oil, biochar and gas; (iii) modelling and machine-learning tools; and (iv) energy-system deployment of pyrolysis products. Throughout, the emphasis is on how characterisation and modelling inform concrete design choices and on the trade-offs that arise when pyrolysis is considered as part of a wider decarbonisation portfolio. By integrating laboratory-scale characterisation with system-level modelling, this review aligns biomass pyrolysis with several United Nations Sustainable Development Goals (SDGs). The optimisation of thermochemical conversion pathways for forestry and agro-industrial residues directly supports SDG 7 (Affordable and Clean Energy) by enhancing the efficiency of bio-oil and syngas production. Furthermore, the deployment of biochar as a stable carbon sink for negative emissions and soil amendment addresses SDG 13 (Climate Action) and SDG 15 (Life on Land). By converting low-value waste streams into high-value energy carriers and chemicals within a circular bioeconomy framework, the research further contributes to SDG 12 (Responsible Consumption and Production) and SDG 9 (Industry, Innovation and Infrastructure). Full article

Thermochemical/catalytic co-processing of biomass and solid wastes is a promising route for waste valorization, low-carbon energy recovery, and the co-production of fuels, chemicals, and carbon materials. Conventional pathways, including pyrolysis, gasification, liquefaction, and carbonization, provide the basic framework for mixed-feed conversion. Emerging routes, such as flash Joule heating, microwave-assisted conversion, plasma processing, supercritical water treatment, solar-driven systems, and machine-learning-assisted optimization, further expand opportunities for process intensification and selective upgrading. Owing to feedstock complementarity, including hydrogen donation from plastics, catalytic effects of ash minerals, and interactions among reactive intermediates, co-processing can enhance deoxygenation, hydrogen generation, aromatization, and carbon utilization. Major challenges remain, however, including feedstock heterogeneity, reactor scale-up, catalyst stability, and the limited transferability of laboratory-scale synergy to realistic waste streams. Future progress should therefore focus on continuous validation, mechanistic clarification, and integrated techno-economic, life-cycle, and data-driven assessments. Full article

Accurate prediction of syngas composition is essential for process design, optimization, and scale-up, yet it remains challenging due to interactions among operating conditions, biomass properties, and chemical reactions. This study used a database of 450 experimental observations spanning a wide range of biomass feedstocks and operating conditions to compare the predictive performance of Aspen Plus simulations and Machine Learning models in estimating the concentrations of CO, CO₂, H₂, and CH₄ in syngas. Aspen Plus was used to simulate the 4 stages of the biomass gasification process under different operating conditions, with special focus on the three reactor modules (RPlug, RGibbs, and REquil) modeling the last two stages. In parallel, Machine Learning models using four regression algorithms (XGBoost, Support Vector Machines, Random Forest and Artificial Neural Networks), with different preprocessing and data-splitting strategies, were evaluated for predicting syngas composition. The best Machine Learning models achieved R² values of 0.753 (CO), 0.866 (CO₂), 0.879 (H₂) and 0.734 (CH₄) on the test set. These results outperformed the Aspen Plus approach and highlight the potential of Machine Learning models as complementary or alternative tools for modelling biomass gasification. Shapley Additive Explanation analysis identified the most influential input variables, revealing key roles for the steam-to-biomass ratio and the equivalence ratio in predicting syngas composition. This study demonstrates that existing Aspen Plus simulation models require further development to improve performance metrics across a wide range of biomass feedstocks and operating conditions. Full article

This study compares hydrogen production pathways from water—using renewable-powered electrolysis (alkaline, water-based)—and biomass (gasification), under harmonized system boundaries and a common functional unit of 1 kg H₂ at 99.97% purity. It examines technological efficiency and environmental impacts, including cradle-to-gate Life Cycle Assessments (LCAs) of each pathway, focusing on global warming potential (GWP100), water consumption, land use, acidification, cumulative energy demand, and the critical minerals footprint. The analysis highlights the roles of water electrolysis and biomass gasification within South Africa’s energy landscape, considering the integration of renewable electricity, energy quality, and co-product allocation. Economic factors, such as the Levelized Cost of Hydrogen (LCOH), are evaluated alongside environmental indicators. The study emphasises the environmental challenges of biomass gasification, notably water use and emissions, and contrasts these with the climate benefits of renewable-powered electrolysis. It also reviews policy initiatives and government programs that support hydrogen and sustainable energy in South Africa, aligning with the SDGs. Overall, the findings underscore the trade-offs in hydrogen development, emphasising opportunities for resource utilisation while addressing deployment challenges. Full article

Brewer’s spent grain (BSG) is one of the major by-products of the brewing industry and an abundant lignocellulosic stream with potential for energy recovery and broader biorefinery use. This review evaluates the main BSG-to-energy pathways, including anaerobic digestion (AD), combustion/co-combustion, pyrolysis, gasification, and hydrothermal processes (HTC/HTL), with emphasis on technical performance, environmental aspects, implementation constraints, and integration into brewery systems. Particular attention is given to the effect of BSG heterogeneity, high moisture content, protein and ash composition, and storage instability on process selection and operability. In addition to summarizing pathway-specific evidence, the manuscript proposes a harmonized comparative framework and an integrated technical–economic–environmental interpretation of BSG valorization options. The analysis shows that wet-feed-compatible pathways, especially AD and hydrothermal processing, are generally better aligned with the intrinsic properties of fresh BSG, whereas thermochemical routes usually require more intensive feedstock conditioning and tighter control of ash-related and gas cleaning risks. The review also highlights that long-term operational reliability, scale-up constraints, and utility integration are as important as nominal conversion efficiency when assessing practical deployment. Current evidence suggests that the most realistic implementation strategies are context-dependent and should be selected according to brewery scale, energy demand profile, available heat integration, and acceptable operational risk. Future research should prioritize harmonized reporting, long-term industrial validation, and the development of robust hybrid systems and brewery-integrated biorefinery configurations. Full article

Waste tyres, with their high carbon content and heating value that is greater than that of coal and biomass, present a potential feedstock for energy recovery. Similarly, automotive paint sludge (APS) is a hazardous waste rich in volatile and inorganics compounds, making it difficult to dispose of safely, but it also has potential for thermochemical conversion. Gasification is a thermochemical process which can turn such wastes into syngas, a mixture mainly composed of carbon monoxide and hydrogen that can be utilized to generate power and produce liquid fuels. To deal with challenges of single feedstock gasification, co-gasification combines two or more feedstocks, taking advantage of synergistic interactions to enhance syngas yield and overall efficiency. In this work, Aspen Plus simulation software is used to develop a model for the co-gasification of waste tyres and automotive paint sludge. Sensitivity analysis was performed with the aim of investigating and optimizing the overall process conditions of waste tyre and APS co-gasification. This study investigated the effect of air (ER) and water feed (SFR) and blend ratios on the adiabatic reaction temperature, product gas composition and heat value of the product syngas. Optimal operating ranges were identified as ER = 0.35–0.40 and SFR = 1.0–1.2 for tyre gasification, ER ≈ 0.50–0.55 for APS-only gasification, and ER = 0.40–0.48 with SFR = 0.8–1.0 for co-gasification blends. Adiabatic temperatures under recommended conditions were typically 700–800 °C. The LHV of syngas decreased with increasing ER, SFR, and APS fraction, falling from ~13 MJ/kg for tyre gasification to below 10 MJ/kg for APS-rich cases due to oxidation and dilution by CO₂ and ash. No positive synergistic effect in syngas quality was observed under thermodynamic equilibrium conditions. APS primarily acted as an ash-rich, low-carbon diluent, reducing CO concentration, heating value and adiabatic temperature. However, potential catalytic interactions from APS mineral matter, which are not represented in the equilibrium model, may produce synergistic effects in practical gasifiers. Full article

Energy transformation requires the development of distributed renewable energy, in which heat and electricity are produced by small units or production facilities for local needs. One favorable development direction is the thermal conversion of biomass, which is classified as a renewable energy source. Due to the variability of its physicochemical properties, gasification technology offers a flexible and competitive alternative to combustion processes. One of the key challenges associated with biomass gasification is the relatively high concentration of contaminants in the raw producer gas. This article presents the results of pilot studies on producer gas purification using activated carbon fixed-bed adsorption. The pilot studies focused on assessing the effectiveness of this technology in the context of purifying producer gas from biomass gasification installations. During the conducted experimental study, approximately 2.2 kg of contaminants were adsorbed. The calculated unit mass of adsorbed contaminants per unit volume of producer gas was 11.7 g/Nm³. The removal efficiency of contaminants was 61.5% for tar compounds and 83.6% for volatile organic compounds. A 100% removal efficiency was achieved for the analyzed sulfur compounds (H₂S, COS, and CH₃SH). The research showed positive effects of adsorption for final producer gas purification, supporting further experimental research. Full article

Plastic waste gasification offers a dual-benefit pathway for hydrogen production and waste management in emerging economies. However, existing hydrogen infrastructure planning focuses predominantly on blue and green pathways, with limited integration of waste-derived hydrogen or spatially distributed waste availability constraints. This study determines optimal waste-to-hydrogen infrastructure deployment in Oman through 2040 using mixed-integer linear programming with verified techno-economic parameters. Results indicate that plastic waste can produce 21,997 tonnes H₂ annually at a levelised cost of $2.88/kg, competitive with blue hydrogen ($1.80–2.50/kg) and significantly cheaper than current green hydrogen ($4–6/kg). The optimal network comprises four facilities at Muscat (500 TPD), Sohar (128 TPD), Salalah (192 TPD), and Nizwa (67 TPD), processing 275,000 tonnes of plastic waste whilst avoiding 137,000 tonnes of CO₂-eq through landfill diversion. However, feedstock availability constrains production to 24% of base case demand (90,000 tonnes), positioning waste-to-H₂ as a complementary pathway requiring integration with steam methane reforming for industrial hubs and electrolysis for the transport sector. Sensitivity analysis reveals hydrogen yield (±29% cost impact) and CAPEX (±20%) as critical parameters, with cost reduction pathways targeting $2.00–2.30/kg by 2035 through technology learning and co-benefit monetisation. Policy recommendations include extended producer responsibility schemes, government fleet procurement mandates, and regional waste trade agreements across the GCC. Waste-to-hydrogen demonstrates techno-economic viability as a guaranteed baseload contributor within diversified hydrogen strategies for Gulf economies. Full article

Municipal solid waste (MSW) management faces increasing pressure due to rapid urbanization and the need for low-emission energy systems. This study investigates the thermogravimetric gasification behavior of Chinese MSW under CO₂, mixed air-CO₂, and SrMnO₃ (SMO) oxygen-carrier atmospheres to identify pathways for producing clean and higher-quality syngas. Using TGA-QMS, the gasification stages were monitored qualitatively and quantitatively over the temperature range of 750–1000 °C, while complementary FTIR, XRD, SEM-EDS, and ICP-OES analyses were employed to characterize the fresh waste and ash samples. Results show that CO₂ gasification is strongly dependent on temperature and concentration, producing CO via Boudouard reaction, resulting in a gas composition of 73% CO and 27% CO₂. An air-CO₂ mixture as a gasification agent shifted conversion toward combustion, producing high CO during oxidation but suppressing gasification, yielding syngas dominated by 90% CO and 10% CO₂. Introducing SMO significantly altered the reaction pathway via lattice-oxygen transfer: 7–56.75 mg SMO produced up to 97% CO and 3% CO₂, without external oxidants, demonstrating superior per-unit oxidizing capacity compared to CO₂. A mild synergistic effect was observed in the mixed CO₂-SMO investigation, where CO formation exceeded that obtained with CO₂ alone but remained lower than that in SMO-only gasification. In general, SMO-enabled oxygen donation provides a promising low-dilution, high-selectivity route for MSW gasification within thermogravimetric regimes. Full article

Wastewater treatment plants (WWTPs) are among the most energy-intensive components of urban infrastructure. In light of the revised EU directive on municipal wastewater treatment, which targets energy neutrality by 2045, effective energy management in this sector is becoming essential. This article reviews the current knowledge regarding energy consumption in WWTPs and analyses opportunities to increase their energy self-sufficiency by reducing energy demand and recovering energy. Key factors influencing energy consumption are discussed, including facility size, the range of technological processes used, automation level, and equipment condition. Attention is given to aeration systems, which account for the largest share of electricity consumption, and the possibilities for their modernization and optimization using energy-efficient diffusers and advanced process control systems. The potential for recovering chemical energy from sewage sludge is analyzed, with emphasis on anaerobic digestion and co-digestion with other organic wastes. Alternative sludge conversion methods, such as incineration, pyrolysis, gasification, and hydrothermal carbonization, are also presented. The analysis is complemented by technologies for recovering physical energy from wastewater, including the use of thermal energy via heat pumps and hydraulic energy from wastewater flow. The findings indicate that achieving energy self-sufficiency in WWTPs requires site-specific, hybrid solutions combining energy savings with selective energy recovery, considering technical and economic conditions. Full article

Increasing global demand for animal-based protein has created a critical environmental management challenge regarding manure accumulation in intensive livestock production. Gasification offers a sustainable solution by converting organic residues into renewable synthetic gas (syngas) and carbon-rich biochar. This study systematically evaluated the performance of three major types of animal waste—dairy manure, poultry litter, and swine manure—against a lignocellulosic control (wood veneer waste) in a top-lit updraft (TLUD) gasifier. Three airflow rates (10, 15, and 20 L min⁻¹) were studied. The results indicated that increasing airflow significantly elevated the gasifier flame front temperatures, with poultry litter achieving the highest peak temperature (825.5 °C), followed by swine manure and dairy manure (753.7 and 727.0 °C, respectively) at 20 L min⁻¹ airflow. While dairy manure exhibited the fastest linear burning rate (25.7 mm/min), poultry litter demonstrated the highest mass consumption rate (32.8 g/min). Feedstock chemistry drove distinct reaction pathways in syngas composition. Poultry litter emerged as the superior feedstock for H₂ production, achieving a peak H₂ concentration of 10.78% at 20 L min⁻¹, which attributed to a synergistic combination of outstanding temperature, moisture content and catalytic alkali metals that promoted steam reforming and water–gas shift reactions. CO production was dominated by wood veneer (17.6%), which was driven by the dominance of elemental carbon and fixed solid (FS) content that favored partial oxidation and a Boudouard reaction. These findings suggest that while airflow regulates thermal kinetics, the specific energy profile of the produced syngas is fundamentally determined by the physiochemical properties of the biomass precursor. Full article

Catalytic biomass gasification is considered a promising route for the production of hydrogen-rich syngas. However, the impact of catalytic enhancement on gas composition is a complex phenomenon, as experimental outcomes are often strongly dependent on reactor configurations and kinetic effects. To address these challenges, a thermodynamic equilibrium-based modeling approach was developed to theoretically investigate the influence of catalytic enhancement in biomass steam gasification. The gasification process was modeled using Gibbs free energy minimization, focusing on the elemental composition of biomass and the equilibrium distribution among the major gaseous species, namely H₂, CO, CO₂, CH₄, and H₂O. The effects of the different catalyst types, including dolomite, Ni/olivine, and iron-based catalysts, were examined through catalyst-dependent activity coefficients. Simulations were carried out under steam gasification conditions at atmospheric pressure, with particular emphasis on the influence of temperature, steam-to-biomass ratio, and catalyst activity on syngas composition. The results showed that increasing catalyst activity enhanced hydrogen production while suppressing methane formation, primarily through intensified tar reforming and water–gas shift reactions. The model successfully reproduced widely accepted thermodynamic trends reported in the literature. Overall, the proposed framework can provide a flexible and computationally efficient screening-level tool for the theoretical assessment of catalytic effects in biomass gasification, offering valuable insights for preliminary catalyst selection and conceptual process design. Full article