Research progress in biomass thermochemical methanation technology for synthetic natural gas production

Wang, X., Xiao, D., Ding, H., Liu, Z., Li, T., and Xiao, R. (2026). "Research progress in biomass thermochemical methanation technology for synthetic natural gas production," BioResources 21(4), Page numbers to be added.

Abstract

Biomass gasification for synthetic natural gas (SNG) production has emerged as a promising pathway for renewable energy utilization and the low-carbon energy transition. This review comprehensively summarizes the key technologies involved in Bio-SNG conversion, focusing on feedstock pretreatment, gasification, syngas conditioning, and methanation. The influences of typical pretreatment methods, including torrefaction and hydrothermal carbonization, on feedstock reactivity and tar formation are critically analyzed. Furthermore, the effects of different gasifier configurations and gasifying agents in regulating syngas quality are compared in detail. The article systematically elaborates the research progress in tar, sulfur, and chlorine impurity removal, water-gas shift (WGS) reaction and H₂ addition through Power-to-Gas (PtG) for H₂/CO ratio adjustment, Ni-based methanation catalysts, and heat-transfer-intensified reactors. Moreover, the inherent limitations and potential improvement strategies of current technologies are discussed, including instability in gasification performance caused by feedstock variability, catalyst deactivation from multiple impurities, coking and sintering during methanation, and thermal management challenges associated with highly exothermic reactions. Finally, Bio-SNG technology is transitioning from individual process optimization toward integrated and synergistic full-process development, which is expected to facilitate the large-scale commercial deployment of this technology.

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Research Progress in Biomass Thermochemical Methanation Technology for Synthetic Natural Gas Production

Xiyu Wang,^a,+ Deliang Xiao,^a,+ Hong Ding,^b Zhou Liu,^b Tao Li,^a and Rui Xiao,^a,*

DOI: 10.15376/biores.21.4.Wang2

Keywords: Biomass gasification; Synthetic natural gas; Syngas conditioning; Methanation; Ni-based catalysts

Contact information: a: Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 211189, China; b: Jiangsu Guoxin Research Institute Co., Ltd; +X.Y. and X.D. contributed equally to this work

* Corresponding author: [email protected]

INTRODUCTION

Global warming induced by the greenhouse effect has exacerbated climate change, thereby posing severe threats to human society and ecological systems. Anthropogenic greenhouse gases (GHGs) emissions, particularly those originating from fossil fuel combustion, have been recognized as the primary driver of climate change. Consequently, the transition of the energy structure from fossil-based resources to renewable energy sources is of critical importance for climate change mitigation (Sikarwar et al. 2016; Zhang

et al. 2009). Biomass is the only renewable carbonaceous resource that can be directly converted into solid, liquid, and gaseous fuels. Owing to its wide availability, abundant reserves, and inherent carbon-neutral characteristics, biomass is widely regarded as a key component of future sustainable energy systems (Ahmad et al. 2016). According to the International Energy Agency (IEA), modern bioenergy accounted for approximately 55% of global renewable final energy consumption in 2023, exceeding the combined contributions of wind, solar, hydropower, and geothermal energy (Reid et al. 2020). To promote the high-value utilization of biomass in industrial and energy sectors, biomass conversion technologies have been continuously developed and optimized. At present, biomass conversion technologies are generally divided into three main categories: thermochemical conversion, biochemical conversion, and physicochemical conversion (Chen et al. 2021). Among the various biomass utilization pathways, biomass gasification has attracted extensive attention owing to its high energy conversion efficiency, high product flexibility, and broad adaptability to diverse feedstocks. Through thermochemical conversion under controlled operating conditions, biomass can be transformed into synthesis gas rich in H₂, CO, CO₂, and CH₄, which can subsequently be utilized for the production of high-value fuels and chemicals (Valizadeh et al. 2022).

Fig. 1. Biomass thermochemical gasification for preparing natural gas

In recent years, significant progress has been achieved in SNG production from biomass gasification, largely driven by the rapid development of catalytic materials, gasification technologies, and process integration strategies. Nevertheless, several critical challenges remain unresolved, including limited adaptability to diverse biomass feedstocks, catalyst deactivation induced by syngas impurities, and difficulties associated with thermal management during the methanation process. Accordingly, this review provides a comprehensive overview of the key technologies involved in the Bio-SNG conversion pathway, with particular emphasis on feedstock pretreatment, gasification processes, syngas purification and conditioning, as well as methanation catalysts and reactor design. In addition, the major technical bottlenecks and future development trends are critically analyzed, thereby providing insights into process optimization and large-scale commercial deployment.

BIOMASS GASIFICATION FUNDAMENTALS

Feedstock Targeted Pretreatment

Major biomass feedstocks available in China primarily include crop straw, woody biomass, manure, municipal solid waste, and industrial organic waste (Zhang et al. 2018). Figure 2 illustrates major pretreatment methods employed for biomass gasification. Among these technologies, torrefaction and hydrothermal carbonization are regarded as key pretreatment approaches for biomass methanation processes, particularly for feedstocks dominated by agricultural and forestry residues and high-moisture biomass (Wang et al. 2022; Niu and Shen 2022; Huang et al. 2023; Shen 2024). Manatura et al. (2017) confirmed that torrefaction can increase the proportion of combustible components in syngas from the perspective of product distribution. In addition, Peng et al. (2025) demonstrated through a comparative study that wet torrefaction exhibits superior performance over dry torrefaction in terms of deoxygenation and alkali metal removal, accordingly, wet torrefaction presents greater applicability advantages for straw-derived feedstocks with high ash content. Koprivica et al. (2024) prepared hydrochar using paulownia leaves as feedstock and reported that hydrochar produced under high-temperature conditions exhibits higher energy density and improved thermal stability, thereby resulting in enhanced gasification reactivity.

Fig. 2. Pretreatment methods for biomass steam gasification (with permission from Elsevier, Shen 2024)

From a mechanistic perspective, torrefaction mainly suppresses tar formation by reducing the O/C atomic ratio and volatile matter content, whereas hydrothermal carbonization improves feedstock energy density and reaction stability through structural reconfiguration under hydrothermal conditions. These two pretreatment strategies, respectively, enhance gasification performance from the perspectives of reaction pathway regulation and feedstock adaptability. However, existing studies have predominantly focused on the effects of pretreatment on gasification behavior, while a systematic understanding of the coupled mechanisms through which pretreatment influences syngas composition and the stability of methanation catalysts remains insufficient.

Gasifier Type and Gasifying Agent Selection

Biomass gasification is fundamentally characterized as a coupled process of multi-step redox reactions, which generally proceeds through four sequential stages: drying, pyrolysis, oxidation, and reduction (Hussain et al. 2025). The gasifier serves as the core reactor for facilitating and sustaining these reaction pathways. Based on variations in feeding configuration, gas-solid contact mode, and reaction temperature, biomass gasifiers are commonly classified into fixed-bed, fluidized-bed, entrained-flow, and plasma gasification systems (Rey et al. 2024). Schematic representations of these gasifier types are presented in Fig. 3.

Fig. 3. (a) Updraft gasifier, (b) downdraft gasifier, (c) fluidized bed gasifier, (d) circulating fluidized bed gasifier, (e) dual fluidized bed gasifier

In methanation-oriented processes, gasifier selection is essentially governed by the trade-off between tar mitigation capability and heat transfer performance. This is driven by stringent requirements for high-quality syngas with low tar content and stable composition. Among the available gasifier configurations, fluidized-bed gasifiers have emerged as the predominant technology for industrial-scale Bio-SNG production, with successful demonstrations in a 140 MW forestry residue gasification facility in Finland and an 8 MW steam gasification combined heat and power (CHP) plant in Austria. Fixed-bed gasifiers, despite their structural simplicity and relatively low capital investment, are constrained by high tar yields and relatively poor operational stability, thereby limiting their application to small-scale systems. In contrast, entrained-flow gasifiers are capable of producing low-tar, high-quality syngas; however, their requirements for high operating temperatures, elevated energy consumption, and substantial capital investment render them more suitable for large-scale centralized applications. Accordingly, in methanation-targeted processes, gasifier selection must be determined not only by gasification efficiency but also by downstream gas-cleaning demands and catalyst stability requirements.

Beyond syngas quality, long-term operation is also limited by ash-related issues, including slagging, fouling, and alkali deposition, which may reduce heat-transfer efficiency and increase maintenance requirements. The severity of slagging and fouling is strongly dependent on biomass composition, particularly the contents of alkali metals, chlorine, and ash-forming minerals.

The selection of gasifying agents exerts a decisive influence on syngas composition, calorific value, nitrogen dilution, tar formation, and overall system energy balance. Air, oxygen, and steam are the most widely applied gasifying agents in biomass gasification systems. The compositional characteristics of syngas produced using different gasifying agents are summarized in Table 1. Steam gasification not only enhances H₂ yield and syngas calorific value while mitigating the dilution effect of N₂ on CH₄ formation, but more importantly, it facilitates the generation of an H₂/CO ratio that is favorable for methanation reactions, thereby reducing the burden of downstream gas conditioning (Mishra and Upadhyay 2021; Abioye et al. 2025). By contrast, air gasification introduces a substantial amount of nitrogen, which lowers syngas calorific value and dilutes reactive species, rendering it generally unsuitable for direct methanation applications. Furthermore, supercritical water gasification (SCWG) enables highly efficient biomass conversion under supercritical conditions of water, and is particularly suitable for high-moisture feedstocks, as it eliminates the drying step while achieving relatively high gasification efficiency at comparatively lower temperatures. This technology has been systematically reviewed by Ciuffi, Shayan, Hu, and co-workers (Shayan et al. 2018; Ciuffi et al. 2020; Hu et al. 2020).

Table 1. Characteristics of Syngas Components under Different Gasifying Agents (Mishra and Upadhyay 2021; Abioye et al. 2025)

Key Operating Parameters

The thermodynamic equilibrium, reaction kinetics, and product distribution of biomass gasification are collectively governed by multiple operating parameters, among which temperature, equivalence ratio (ER), and steam-to-biomass ratio (S/B) are considered the most critical. ER is defined as the ratio of the actual air supply to the theoretical air demand, whereas S/B represents the ratio of steam to biomass fed into the gasifier. Significant nonlinear coupling relationships exist among these parameters, and their variations not only determine the redox equilibrium and reaction rates within the gasification zone but also directly influence key performance indicators, including tar formation, syngas composition, cold gas efficiency (CGE), and carbon conversion efficiency. These effects have been experimentally validated (Jangsawang et al. 2015; Jayathilake et al. 2017).

Elevated gasification temperatures (800 to 900 °C) favor endothermic gasification reactions and promote tar cracking and secondary reactions, thereby improving syngas quality; this phenomenon has been extensively reported in previous studies (Matsumura 2002; Luo et al. 2009; He et al. 2009; Taba et al. 2012; Wongsiriamnuay et al. 2013; Reddy et al. 2014). The optimal ER is generally considered to fall within the range of 0.2 to 0.4. Excessively high ER values result in the further oxidation of H₂ and CO into H₂O and CO₂, respectively, while the introduction of large amounts of N₂ causes dilution of the product gas. Conversely, excessively low ER values lead to incomplete gasification and increased char formation (Safarian et al. 2021; Loweski et al. 2024). With increasing S/B, the concentrations of H₂ and CO₂ generally increase, whereas the contents of CO and CH₄ decrease correspondingly. Therefore, S/B is commonly maintained within the range of 0.3 to 1.0 to achieve a balance between reaction efficiency and energy consumption (Mishra et al. 2021; Cortazar et al. 2023). Notably, the optimization of gasification parameters should not focus solely on a single performance indicator; instead, it should instead be performed through multi-objective optimization based on downstream methanation requirements.

Although the effects of temperature, ER, and S/B on gasification performance have been relatively well established, existing studies have predominantly focused on single-factor analyses under specific feedstock and gasifier conditions, resulting in a limited systematic understanding of multi-parameter coupling effects. Consequently, the development of intelligent optimization models integrating feedstock characteristics with reaction kinetics will likely become a key research direction for achieving efficient and stable operation of biomass gasification systems.

SYNGAS CONDITIONING

The raw syngas generated from biomass gasification contains a variety of harmful impurities that must be effectively removed prior to entering the methanation reactor. These contaminants not only induce operational problems, including equipment corrosion, pipeline fouling, and catalyst deactivation, but may also result in secondary environmental pollution (Romar et al. 2013; Abdoulmoumine et al. 2015; Marcantonio et al. 2021; Matej et al. 2025). Table 2 summarizes the upper limits of pollutants in gasified syngas for different applications. For methanation processes, the primary objective of impurity control is not merely to satisfy conventional industrial fuel gas standards, but to achieve ultra-low impurity concentrations below the tolerance limits of methanation catalysts.

Table 2. Upper Limits of Pollutants in Gasified Syngas in Different Applications (Romar et al. 2013; Abdoulmoumine et al. 2015; Marcantonio et al. 2021; Matej et al. 2025)

Impurity Removal

Hot gas cleaning and catalytic cracking technologies can effectively reduce the concentrations of particulate matter and tar in syngas, thereby improving syngas purity and enhancing its suitability for downstream methanation processes. Rey et al. (2024) systematically evaluated the purification performance of cyclone separators, bag filters, and electrostatic precipitators, and reported that all of these devices achieved particulate removal efficiencies exceeding 90% for particles larger than 5 μm. Fu et al. (2025) conducted hot gas cleaning experiments in a pilot-scale two-stage fluidized-bed gasification system and demonstrated that a catalytic cracking unit employing an iron-based bauxite residue catalyst could achieve tar removal efficiencies of 82.8 to 98.0% under appropriate operating temperatures. Furthermore, Abdelaal et al. (2023) reported that the synergistic effects of adsorption and catalysis, combined with steam reforming reactions, enabled tar removal efficiencies of up to 99% in gasification char-based systems. Nevertheless, light aromatic hydrocarbons and carbon deposition precursors generated during tar cracking may still exert adverse effects on downstream methanation catalysts.

Sulfur-containing compounds constitute one of the major contaminants in syngas. Existing desulfurization technologies are predominantly operated under atmospheric pressure and low-temperature conditions. They are generally classified into wet purification and dry adsorption processes. Wet purification achieves efficient sulfur removal through physical absorption or chemical reactions (Rahim et al. 2023). Compared with conventional coal-derived syngas systems, biomass-derived syngas contains more complex sulfur species, such as COS and thiols, thereby increasing the difficulty of sulfur removal. Sánchez-Hervás et al. (2023) and Frilund et al. (2020) experimentally investigated the desulfurization performance of ZnO-based adsorbents for biomass-derived syngas, and both studies demonstrated favorable sulfur removal performance, indicating their potential as alternatives to traditional wet desulfurization processes. N- and Cl-containing species in low-temperature syngas are highly water-soluble; consequently, industrial applications commonly employ wet scrubbing processes based on water washing to achieve their simultaneous removal. Water washing therefore remains the most widely adopted purification method for such light-component impurities (Rey et al. 2024).

Current purification studies primarily consider tar removal, desulfurization, and dechlorination as separate unit operations, and lack systematic integration toward multi-pollutant synergistic control. In particular, the diversity of biomass feedstocks results in substantial fluctuations in syngas impurity composition. Therefore, the development of flexible purification systems capable of accommodating seasonal variations in feedstock characteristics represents a critical challenge that must be addressed in future engineering practice.

H₂/CO Ratio Regulation

The composition of syngas derived from biomass gasification generally fails to satisfy the stoichiometric requirements of methanation reactions, thereby necessitating regulation of the H₂/CO ratio. For methanation processes, the principal reaction pathways can be expressed as follows:

CO + 3H₂ → CH₄ + H₂O (ΔH° = -206.1 kJ/mol) (1)

CO₂ + 4H₂ → CH₄ + 2H₂O (ΔH° = -165 kJ/mol) (2)

CO + H₂O → CO₂ + H₂ (ΔH° = -441.2 kJ/mol) (3)

The effective H₂/CO ratio is more commonly employed as an evaluation criterion in industrial applications. Its theoretical value generally must be no less than 3.0. Biomass gasification syngas typically has insufficient H₂ content or excessive CO₂ concentration, both of which limit methane production efficiency (Santana et al. 2025). Notably, CO and H₂ exhibit a competitive relationship in the WGS reaction; while enhancement of H₂ production is accompanied by a reduction in CO concentration, consequently suppressing the CO methanation pathway. Therefore, H₂/CO ratio regulation is essentially a synergistic optimization problem for the two methanation pathways (CO and CO₂).

WGS is a common method for adjusting the H₂/CO ratio in syngas. Tiwari, Duke, Chen, and co-workers (Tiwari et al. 2014; Duke et al. 2017; Chen et al. 2018) systematically investigated low-temperature WGS strategies, with particular emphasis on the effects of catalyst nanostructure and synthesis methods on hydrogen production efficiency. They discovered that reducing active metals (e.g., Pt, Rh, Au) to single-atom catalyst (SAC) or sub-nanometer cluster scales can significantly lower activation energy, maximize active site utilization, and substantially enhance CO conversion while suppressing methanation side reactions. Liu et al. (2025) proposed an ultra-high-temperature WGS strategy, which simplifies the conventional multistep process requiring the integration of high- and low-temperature shift stages to overcome thermodynamic and kinetic limitations. This approach reduces thermal losses and is particularly suitable for high-pressure, low-tar syngas generated from biomass gasification. Ma et al. (2018) synthesized Cu/Fe oxide catalysts with nanorod structures using a coprecipitation method, and the prepared catalysts exhibited favorable activity during high-temperature WGS reactions. Zhao et al. (2019) further developed a solar-driven WGS approach, in which CuO_x/Al₂O₃ achieved an H₂ generation rate of 122 μmol·gcat⁻¹·s⁻¹ and a CO conversion of 95% under illumination conditions. In addition to eliminating electricity consumption costs, this solar-driven hydrogenation process enabled the conversion of approximately 1.1% of solar energy into usable chemical energy.

In addition to WGS, hydrogen supplementation is another significant pathway for regulating the H₂/CO ratio. By introducing hydrogen produced via water electrolysis (e.g., alkaline or solid oxide electrolysis), the H₂ content in syngas can be substantially increased, promoting the CO₂ methanation reaction and thereby enhancing overall methane yield. This pathway is particularly suitable for PtG systems that operate in conjunction with renewable energy sources such as wind and photovoltaics. Gassner and Maréchal (2008) theoretically proposed the technical route of external hydrogen supplementation in 2008. Due to the rational utilization of hydrogen during the methanation process, the introduction of electrolyzers can improve the energetic and thermal efficiencies of the system. Alamia et al. (2017) simulated the integration of hydrogen into an optimized GoBiGas plant and calculated the cold gas efficiency for SNG production to be between 70% and 73%. Suaad et al. (2025) utilized Aspen Plus to simulate three regulation scenarios for the low H₂/CO problem in syngas: WGS, supplemental green hydrogen, and separation-recombination. The simulation results indicated that the WGS scenario yielded the highest methane production rate, supplemental green hydrogen was suitable for integration with renewable electricity, while separation-recombination exhibited lower efficiency. Currently, various alternative schemes for integrating hydrogen into the SNG production process have been proposed. For instance, Menin et al. (2023) and Giglio et al. (2021) integrated alkaline water electrolysis and solid oxide electrolysis, respectively, into biomass-to-methane processes, thereby improving cold gas efficiency.

Overall, the WGS pathway offers the advantages of technological maturity and the absence of additional hydrogen requirements; however, it remains constrained by thermodynamic equilibrium limitations and CO consumption losses. In contrast, external hydrogen supplementation can substantially enhance methane yield and promote CO₂ utilization, although its large-scale application is currently restricted by the high cost of hydrogen production. Consequently, future developments should focus on the establishment of flexible regulation systems integrating WGS and external hydrogen supplementation, thereby enabling dynamic optimization of the H₂/CO ratio.

SYNGAS METHANATION

Reaction Mechanism and Thermodynamic Fundamentals

The methanation reactions of CO and CO₂ (Eqs. 1 and 2) are highly exothermic. As the reaction temperature increases, the equilibrium constant of the system significantly decreases, thereby suppressing methane formation in high-temperature regions. Consequently, while higher temperatures favor increased reaction rates, thermodynamic constraints often result in a declining trend in methane selectivity. The CO₂ methanation reaction is a linear combination of the CO methanation reaction and the reverse water-gas shift reaction. In practical production, when using nickel catalysts, the CO methanation reaction generally occurs concurrently. However, if the CO concentration exceeds a certain threshold, the conversion of CO₂ becomes inhibited (Miao et al. 2016). At the kinetic level, both CO and CO₂ methanation generally follow a Langmuir-Hinshelwood-type mechanism, in which reactants are initially adsorbed onto the catalyst surface and subsequently undergo stepwise hydrogenation reactions. Extensive studies have reported that the rate-determining step in CO methanation is commonly associated with the sequential hydrogenation of surface carbon species, whereas CO₂ methanation generally proceeds through an indirect CO₂→CO→CH₄ pathway. In multicomponent systems, CO molecules exhibit stronger competitive adsorption toward active sites, thereby suppressing the activation and conversion of CO₂ to a certain extent (Miao et al. 2016; Schmider et al. 2021; Celoria et al. 2025). Therefore, efficient CO₂ conversion in CO-rich systems requires mitigation of competitive adsorption effects through modulation of catalyst surface electronic structures or optimization of reaction conditions.

Schmider et al. (2021), based on fixed-bed experiments and kinetic fitting analyses, showed that Ni-catalyzed methanation of CO and CO₂ involves different initial pathways, whereas CO methanation mainly proceeds via H-assisted CO dissociation, whereas CO₂ is first hydrogenated to COOH and then converted to CO. (Fig. 4).

Fig. 4. Reaction-flow analysis of (a) CO and (b) CO₂ methanation over Ni-based catalysts. Percentages indicate relative reaction fluxes under the respective conditions; the orange box denotes the primary reactant. (Schmider et al. 2021).

Accordingly, CO and CO₂ methanation pathways are intrinsically coupled, and their conversion efficiencies are jointly governed by catalyst intrinsic activity, syngas composition, and reaction conditions.

Catalyst Systems

The deactivation of methanation catalysts primarily results from the synergistic effects of multiple mechanisms, including carbon deposition, sulfur poisoning, metal sintering, and impurity contamination. Carbon deposition and sintering are associated with structural degradation, whereas sulfur-, chlorine-, and other impurity-induced deactivation primarily involve chemical poisoning of active sites. For biomass-derived syngas, tar species can polymerize on Ni surfaces to form carbonaceous deposits, resulting in active-site blockage and inhibited reactant adsorption. Meanwhile, sulfur-containing compounds (e.g., H₂S and COS) strongly interact with metallic Ni sites and generate nickel sulfides, leading to irreversible activity loss. Chlorine-containing species may further modify metal–support interactions and accelerate Ni migration and sintering. Therefore, industrial catalyst development requires a balance among activity, impurity tolerance, regeneration capability, and long-term stability. Although oxidation–reduction treatments and coke removal can partially restore activity, repeated regeneration may alter metal dispersion and support structure, making intrinsic resistance toward deactivation more desirable. However, repeated regeneration may alter metal dispersion and support structure, resulting in gradual activity loss during long-term operation. Therefore, improving intrinsic resistance toward deactivation remains more favorable than relying solely on regeneration.

Methanation catalysts are generally composed of active metal species dispersed on porous supports. Among various catalytic systems, Ni-based catalysts remain dominant in industrial applications owing to their high activity, excellent methanation selectivity, and economic advantages (Xing et al. 2020). Recent studies have mainly focused on optimizing Ni catalysts through support modification, with Al₂O₃, CeO₂, SiO₂, ZrO₂, and TiO₂ being widely investigated. Findings indicate that Al₂O₃ promotes high dispersion of active species owing to its high surface area, thereby enhancing methanation performance. However, its acidic sites may promote carbon formation, thereby compromising catalyst stability (Liu et al. 2017; Wang et al. 2017; Ren et al. 2020). Tables 3 and 4 summarize the catalytic performances of various Ni-based catalysts in CO and CO₂ methanation reactions. Liu et al. (2017) prepared highly active Ni-based catalysts supported on Al₂O₃, ZrO₂, and CeO₂ using a co-precipitation method, and systematically evaluated their methanation performances through a series of characterization and catalytic experiments (Fig. 5). Among these catalysts, Ni/Al₂O₃ exhibited the most favorable methanation performance.

Fig. 5. TEM images of the reduced nickel-based catalysts: (a) Ni/Al₂O₃; (b) Ni/ZrO₂; (c) Ni/CeO₂ (With permission from Elsevier, Liu et al. 2017)

In addition to Ni-based catalysts, non-noble-metal systems based on Co, Fe, and Mo have also demonstrated considerable potential. Co-based catalysts exhibit lower carbon deposition tendencies and improved sintering resistance compared with Ni catalysts, while Co-Fe bimetallic systems have demonstrated high CO conversion and CH₄ selectivity at 300 to 450 °C (Eldesouki et al. 2025). Fe-based catalysts possess stronger CO₂adsorption capacity and are therefore more suitable for CO₂-rich systems. Furthermore, the formation of iron carbides (e.g., Fe₃C), can regulate reaction pathways and suppress carbon deposition (Zhang et al. 2023; Zhu et al. 2025). Mo-based catalysts are generally present in the form of Mo₂C, which exhibits an electronic structure analogous to that of noble metals, thereby facilitating CO₂ activation and providing strong resistance against coking (Sae-tang et al. 2024). Nevertheless, the overall catalytic activity and industrial maturity of these catalyst systems remain inferior to those of Ni-based catalysts, and they are currently more commonly employed as promoters or synergistic components in bimetallic catalyst systems.

Table 3. Catalytic Activity of Different Nickel-based Catalysts for CO Methanation

Table 4. Catalytic Activity of Different Nickel-based Catalysts for CO₂ Methanation

Precious-metal catalysts, including Ru, Rh, Pt, and Pd, exhibit excellent low-temperature catalytic activity, high resistance to carbon deposition, and improved tolerance toward catalyst poisoning, making them particularly suitable for low-temperature startup and dynamically fluctuating operating conditions (Vieira et al. 2023). Panagiotopoulou et al. (2008) demonstrated that, in Al₂O₃-supported systems, the methanation activities of Ru and Rh were significantly higher than those of Pt and Pd. Lysne et al. (2024) showed that Rh-promoted Ni-Co/Mg(Al)O catalysts possessed superior tar suppression capability and rapid in situ activation characteristics. Despite their superior catalytic performance, the high cost and limited availability of precious metals significantly restrict their large-scale industrial deployment. Therefore, these catalysts are mainly considered for high-value applications, such as modular Power-to-Gas (PtG) systems, where enhanced activity and operational flexibility are more critical than catalyst cost.

Fig. 6. (a) Effects of noble metal additives (Pt/Pd/Rh), (b) loading amounts of Ni + Co (20 to 40 wt.%), (c) calcination temperature (600 to 800°C) on the steam reforming performance of bio-syngas tar (Lysne et al. 2024).

For industrial methanation applications, improving catalyst economic feasibility requires not only reducing active metal consumption but also extending catalyst lifetime through enhanced resistance toward poisoning and thermal degradation. Current strategies mainly focus on reducing precious-metal loading through high-dispersion techniques, developing low-cost and robust supports, and introducing inexpensive promoters to enhance structural stability and resistance against deactivation. More importantly, improving anti-coking and anti-sintering properties is essential for extending catalyst lifetime and reducing replacement costs during long-term operation. Future studies should therefore prioritize catalyst durability evaluation under realistic biomass-derived syngas conditions, including long-term stability tests, regeneration cycles, and dynamic operating environments, to bridge the gap between laboratory-scale performance and industrial application.

Methanation Reactors and Process Optimization

Owing to the highly exothermic nature of methanation reactions, effective thermal management and temperature uniformity are more critical than simply increasing the reaction temperature. Excessive local heating may accelerate catalyst sintering, carbon deposition, and undesired side reactions, thereby reducing methane selectivity and shortening catalyst lifetime. Several early methanation technologies developed for coal- and biomass-derived syngas, including the Linde, Davy, Lurgi, and TREMP™ processes (Fig. 7), have been extensively implemented in industrial coal-to-SNG plants. However, these reactor systems generally suffer from significant axial and radial temperature gradients, resulting in hotspot formation and accelerated catalyst deactivation. Therefore, multiple reaction stages combined with intermediate cooling are commonly required to regulate temperature rise, which inevitably increases process complexity and capital investment.

Fig. 7. The (a) Linde, (b) Davy, (c) Lurgi, and (d) TREMP^TM methanation processes

Several reactor configurations have been proposed to improve temperature uniformity. Multistage adiabatic reactors with intermediate cooling can effectively distribute the heat release among different reaction zones, whereas actively cooled reactors, heat-exchanger integrated reactors, and microchannel reactors provide enhanced heat removal capability. In addition, structured catalysts and improved catalyst bed designs can reduce local temperature gradients by improving heat and mass transfer.

Among various reactor configurations, fluidized-bed reactors have attracted considerable attention for biomass-derived syngas methanation due to their excellent gas–solid mixing characteristics and superior heat-transfer performance. Figure 8 illustrates the internal configuration of a fluidized-bed reactor. The isothermal fluidized-bed methanation process developed by the Paul Scherrer Institute (PSI) in Switzerland (Rehling et al. 2011) has been successfully validated in MW-scale Bio-SNG facilities, exhibiting stable operation and enhanced tolerance toward complex biomass-derived syngas. Furthermore, circulating fluidized-bed (CFB) and dual fluidized-bed (DFB) systems can further enhance heat transfer efficiency and reaction uniformity through intensified particle circulation and stronger reaction coupling. Nevertheless, fluidized-bed reactors also face several engineering challenges, including additional energy consumption associated with particle circulation, increased gas compression requirements, and catalyst attrition during long-term operation.

Overall, fixed-bed reactors are more suitable for large-scale centralized methanation due to their simplicity, operational maturity, and relatively low mechanical complexity. In contrast, fluidized-bed reactors provide superior thermal management and adaptability to fluctuating biomass syngas; however, additional energy consumption for particle circulation and compression remains a limitation. Nevertheless, improved thermal management and reduced catalyst deactivation risk can compensate for these penalties during large-scale continuous Bio-SNG production.

Fig. 8. Schematic diagram of a fluidized-bed reactor

Beyond fluidized-bed configurations, advanced reactor designs incorporating intensified heat-transfer strategies have been increasingly investigated to address the challenges associated with highly exothermic methanation reactions. Microchannel reactors exhibit excellent thermal management capability due to their extremely short heat-transfer pathways and high surface-area-to-volume ratios, enabling rapid heat removal under highly exothermic conditions. However, their practical application at industrial scale remains limited by high fabrication costs, restricted throughput, and difficulties associated with catalyst loading and replacement. Plate heat exchanger reactors provide compact configurations and efficient coupling between reaction and heat exchange processes, but their complex structure and manufacturing requirements may hinder large-scale deployment. In contrast, slurry-bed reactors utilize the high heat capacity of liquid-phase media to achieve near-isothermal operation and demonstrate improved adaptability toward fluctuating biomass-derived syngas compositions; however, catalyst separation, recovery, and long-term operational stability remain critical challenges.

Beyond reactor optimization, integration of renewable heat sources provides another pathway to reduce the carbon intensity of Bio-SNG production. Concentrated solar thermal (CST) energy can supply part of the heat required for biomass gasification and steam generation, thereby reducing external fossil energy consumption. However, solar-assisted SNG systems still face challenges associated with intermittency, thermal storage requirements, system complexity, and economic feasibility. Future studies should therefore focus on improving heat integration and evaluating the techno-economic performance under realistic operating conditions.

Techno-economic and Environmental Considerations of Bio-SNG Production

Although biomass-derived SNG is generally considered a renewable substitute for fossil natural gas, its commercial viability remains strongly influenced by energy consumption, process integration, and economic performance. As summarized in Table 6, different Bio-SNG pathways exhibit substantial variations in energy efficiency, production cost, and techno-economic feasibility, depending on the degree of process integration and external energy input. The gas cleaning section, particularly deep removal of sulfur, chlorine, tar, and alkali species, represents a major cost contributor because stringent purification is required to protect downstream methanation catalysts. In addition, Power-to-Gas assisted methanation requires external renewable hydrogen, which can significantly increase both capital investment and operational expenditure. Therefore, the environmental benefits of Bio-SNG depend strongly on hydrogen production pathways, process heat integration, and overall system efficiency. Life-cycle assessments have demonstrated that biomass-based SNG can achieve substantial greenhouse gas reductions compared with fossil natural gas; however, these advantages may decrease when energy-intensive upgrading steps or fossil-derived electricity are incorporated. The techno-economic comparison of representative Bio-SNG pathways is presented in Table 6. Although gasification-based SNG routes generally exhibit technological maturity, their economic performance remains strongly affected by syngas upgrading requirements, hydrogen supplementation, and electricity costs. Future commercialization should therefore prioritize integrated process optimization, renewable heat utilization, and reduction of auxiliary energy demand.

The environmental impacts of different Bio-SNG configurations are summarized in Table 7. Despite the improved carbon recovery achieved by integrating renewable hydrogen, the environmental superiority of Power-to-SNG pathways is not unconditional. However, the additional electricity demand associated with water electrolysis introduces substantial energy penalties, which may offset the environmental advantages of PtG-assisted Bio-SNG when renewable electricity availability is limited. Katla-Milewska et al. (2024) pointed out that electrolytic hydrogen supplementation significantly improves carbon recovery in SNG production; however, the electrolyzer becomes the dominant contributor to capital expenditure, increasing the total system cost by approximately 2 to 3 times. In particular, when renewable electricity is obtained from high-cost or carbon-intensive grids, the expected climate benefits may be substantially reduced. Therefore, future Bio-SNG deployment should prioritize scenarios with abundant low-cost renewable electricity and highly integrated heat management rather than universal hydrogen supplementation.

Table 6. Comparison of Techno-Economic Performance among Different Bio-SNG Pathways

Table 7. Environmental Evaluation of Different Technical Routes

CONCLUSIONS AND OUTLOOK

Overall, the integrated process of biomass gasification and methanation exhibits considerable potential for renewable gas production. However, its technological maturity is still limited by several technical challenges. From a reaction mechanism perspective, methanation is an inherently exothermic reaction, and its performance is jointly governed by thermodynamic limitations and kinetic processes. At the catalyst level, Ni-based catalysts dominate due to their cost-effectiveness and high catalytic activity; however, their resistance to coking and poisoning still requires improvement. In terms of reaction engineering, balancing high selectivity and efficient heat transfer is pivotal for achieving stable operation. Furthermore, the presence of impurities in the syngas exacerbates catalyst long-term stability problems. Consequently, current research is increasingly shifting from individual catalyst optimization toward integrated catalyst-reactor system design, thereby facilitating improvements in overall process efficiency.

Established demonstration and pilot-scale biomass methanation projects worldwide have demonstrated the feasibility of Bio-SNG technology. Nevertheless, large-scale deployment and commercialization continue to face challenges related to cost, technology, and system integration. Addressing these challenges is in line with technological development trends. Future advances in biomass gasification-methanation systems will require coordinated advances in multiple areas, including catalyst structural control, enhanced resistance to deactivation, intensified reactor design, and system integration. At the catalyst level, a focus on atomic and interfacial scales may enable the development of catalytic systems with high dispersion and stable metal-support interactions, thereby balancing high activity with resistance to coking and poisoning. In reaction engineering, further efforts should focus on reactor optimization and heat transfer intensification. Concurrently, the integration of gasification and methanation processes, along with synergistic development with renewable hydrogen production technologies, will provide new pathways for enhancing system energy efficiency and achieving circular utilization of carbon resources. Moreover, developing process control strategies with dynamic response capabilities is crucial for addressing challenges posed by feedstock fluctuations and operational condition variations in actual industrial settings. Integrated multi-scale optimization is expected to drive biomass gasification–methanation technology toward efficient, stable, and large-scale applications.

ACKNOWLEDGMENTS

The authors sincerely express gratitude to all participants who contributed to this research. This work was financially supported by Jiangsu Guoxin Research Institute. To enhance the readability and academic rigor of the text, this paper utilized Gemini and ChatGPT (OpenAI) as an auxiliary tool during the English translation and language refinement process.

REFERENCES CITED

Abdelaal, A., Antolini, D., Piazzi, S., Patuzzi, F., Villot, A., Gerente, C., and Baratieri, M. (2023). “Steam reforming of tar using biomass gasification char in a pilot-scale gasifier,” Fuel 351, article 128898. https://doi.org/10.1016/j.fuel.2023.128898

Abdoulmoumine, N., Adhikari, S., Kulkarni, A., and Chattanathan, S. A. (2015). “A review on biomass gasification syngas cleanup,” Applied Energy 155, 294-307. https://doi.org/10.1016/j.apenergy.2015.05.095

Abioye, K. J., Rajamanickam, R., Ogunjinmi, T., Paul, S., Selvasembian, R., and Ighalo, J. O. (2025). “Advancements in biomass waste conversion to sustainable biofuels via gasification,” Chemical Engineering Journal 505, article 159151. https://doi.org/10.1016/j.cej.2024.159151

Ahmad, A. A., Zawawi, N. A., Kasim, F. H., Inayat, A., and Khasri, A. (2016). “Assessing the gasification performance of biomass: A review on biomass gasification process conditions, optimization and economic evaluation,” Renewable and Sustainable Energy Reviews 53, 1333-1347. https://doi.org/10.1016/j.rser.2015.09.030

Alamia, A., Ósk Gardarsdóttir, S., Larsson, A., and Thrän, D. (2017). “Efficiency comparison of large-scale standalone, centralized, and distributed thermochemical biorefineries,” Energy Technology 5(9), 1435-1448. https://doi.org/10.1002/ente.201600719

Battulga, B. U., Bold, T., and Byambajav, E. (2020). “Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation-co-precipitation method,” International Journal of Chemical Reactor Engineering 18(10), article 20200076. https://doi.org/10.1515/ijcre-2020-0076

Battulga, B. U., Chuluunsukh, M., and Byambajav, E. (2020). “Methanation of syngas over Ni-based catalysts with different supports,” Advances in Chemical Engineering and Science 10(2), 113-122. https://doi.org/10.4236/aces.2020.102008

Celoria, F., Salomone, F., Tauro, A., Gandiglio, M., Ferrero, D., Champon, I., Geffraye, G., Pirone, R., and Bensaid, S. (2025). “Kinetic study and deactivation phenomena for the methanation of CO₂ and CO-rich mixed syngas on a Ni/Al₂O₃ catalyst,” Chemical Engineering Journal 512, article 162113. https://doi.org/10.1016/j.cej.2025.162113

Chen, W.-H., Lin, B.-J., Lin, Y.-Y., Chu, Y.-S., Ubando, A. T., Show, P. L., Ong, H. C., Chang, J.-S., Ho, S.-H., Culaba, A. B., et al. (2021). “Progress in biomass torrefaction: Principles, applications and challenges,” Progress in Energy and Combustion Science 82, article 100887. https://doi.org/10.1016/j.pecs.2020.100887

Chen, Y., Lin, J., Li, L., Qiao, B., Liu, J., Su, Y., and Wang, X. (2018). “Identifying size effects of Pt as single atoms and nanoparticles supported on FeOx for the water-gas shift reaction,” ACS Catalysis 8(2), 859-868. https://doi.org/10.1021/acscatal.7b02751

Cheng, C., Wu, C., and Shen, D. (2017). “Preparation of different nickel-iron/titania-alumina catalysts for hydrogen/carbon monoxide methanation under atmospheric pressure,” Energy Technology 5(8), 1269-1276. https://doi.org/10.1002/ente.201600514

Ciuffi, B., Chiaramonti, D., Rizzo, A. M., Frediani, M., Rosi, L., and Arcidiacono, F. (2020). “A critical review of SCWG in the context of available gasification technologies for plastic waste,” Applied Sciences 10(18), article 6307. https://doi.org/10.3390/app10186307

Cormos, C. C., Dragan, M., Petrescu, L., Cormos, A. M., Dragan, S., Bathori, A. M., et al. (2024). “Synthetic natural gas (SNG) production by biomass gasification with CO₂ capture: Techno-economic and life cycle analysis (LCA),” Energy 312(000), 11.
https://doi.org/10.1016/j.energy.2024.133507

Cortazar, M., Santamaria, L., Lopez, G., Artetxe, M., Alvarez, J., Amutio, M., Bilbao, J., and Olazar, M. (2023). “A comprehensive review of primary strategies for tar removal in biomass gasification,” Energy Conversion and Management 276, article 116496. https://doi.org/10.1016/j.enconman.2022.116496

Duke, A. S., Xie, K., Brandt, A. J., and Stair, P. C. (2017). “Understanding active sites in the water-gas shift reaction for Pt-Re catalysts on titania,” ACS Catalysis 7(4), 2597-2606. https://doi.org/10.1021/acscatal.7b00086

Eldesouki, M. H., Eldemerdash, U. N., Mohamed, M. M., and El-Moneim, A. A. (2025). “Semi-industrial CO and CO₂ conversion with biochar-supported Fe-based catalysts,” Carbon Resources Conversion 9(2), article 100358. https://doi.org/10.1016/j.crcon.2025.100358

Frilund, C., Simell, P., Kaisalo, N., Kurkela, E., and Lehtonen, J. (2020). “Desulfurization of biomass syngas using ZnO-based adsorbents: Long-term hydrogen sulfide breakthrough experiments,” Energy & Fuels 34(3), 3316-3325. https://doi.org/10.1021/acs.energyfuels.9b04276

Fu, Z., Charchi Aghdam, N., Nekoeian, S., He, J., Cheng, L., Liu, S., Zhang, L., Chao, J., Wei, X., Wang, R., Nagda, B., Zhang, Y., Ma, Z., Ellis, N., Bi, X., Smith, K., Lim, J., Legros, R., and Duo, W. (2025). “Hot syngas cleanup for pilot two-stage fluidized bed steam-oxygen biomass gasification plant,” Bioresource Technology 418, article 131876. https://doi.org/10.1016/j.biortech.2024.131876

Gac, W., Zawadzki, W., Słowik, G., Kuśmierz, M., and Dzwigaj, S. (2021). “The state of BEA zeolite supported nickel catalysts in CO₂ methanation reaction,” Applied Surface Science 564, article 150421. https://doi.org/10.1016/j.apsusc.2021.150421

Gassner, M., and Maréchal, F. (2008). “Thermo-economic optimisation of the integration of electrolysis in synthetic natural gas production from wood,” Energy 33(2), 189-198. https://doi.org/10.1016/j.energy.2007.09.010

Gassner, M., and Marechal, F. (2015). “Thermo-economic process model for thermochemical production of synthetic natural gas (SNG) from lignocellulosic biomass,” Biomass and Bioenergy 33(11), 1587-1604. https://doi.org/10.1016/j.biombioe.2009.08.004

Giglio, E., Vitale, G., Lanzini, A., Santarelli, M., and Leone, P. (2021). “Integration between biomass gasification and high-temperature electrolysis for synthetic methane production,” Biomass and Bioenergy 148, article 106017. https://doi.org/10.1016/j.biombioe.2021.106017

Guo, Z.-K., Gao, S., Xiang, S.-X., Wang, J.-P., Mao, G.-C., Jiang, H.-L., Dong, B.-X., and Teng, Y.-L. (2024). “Mechanochemical synthesis of Ni/MgO dual functional materials at room temperature for CO₂ capture and methanation,” Chemical Engineering Journal 481, article 148599. https://doi.org/10.1016/j.cej.2024.148599

Han, D., Cho, W., and Baek, Y. (2022). “CO₂ methanation of biogas over Ni-Mg-Al: The effects of Ni content, reduction temperature, and biogas composition,” Catalysts 12(9), article 1054. https://doi.org/10.3390/catal12091054

He, M., Hu, Z., Xiao, B., Li, J., Guo, X., Luo, S., Yang, F., Feng, Y., Yang, G., and Liu, S. (2009). “Hydrogen-rich gas from catalytic steam gasification of municipal solid waste (MSW): Influence of catalyst and temperature on yield and product composition,” International Journal of Hydrogen Energy 34(1), 195-203. https://doi.org/10.1016/j.ijhydene.2008.09.070

Hu, Y., Gong, M., Xing, X., Wang, H., Zeng, Y., and Xu, C. C. (2020). “Supercritical water gasification of biomass model compounds: A review,” Renewable and Sustainable Energy Reviews 118, article 109529. https://doi.org/10.1016/j.rser.2019.109529

Huang, W., Zhang, R., Giannis, A., Li, C., and He, C. (2023). “Sequential hydrothermal carbonization and CO2 gasification of sewage sludge for improved syngas production with mitigated emissions of NOx precursors,” Chemical Engineering Journal 454, article 140239. https://doi.org/10.1016/j.cej.2022.140239

Hussain, M. S., Shi, M., Zhang, S., Zhang, Y., Bie, X., Li, Q., Zhang, Y., Lubjuhn, S., Venghaus, S., and Zhou, H. (2025). “Techno-economic and life-cycle assessments of biomass thermochemical conversion into gaseous fuels,” Energy & Environment Nexus 1(1). https://doi.org/10.48130/een-0025-0015

Jangsawang, W., Laohalidanond, K., and Kerdsuwan, S. (2015). “Optimum equivalence ratio of biomass gasification process based on thermodynamic equilibrium model,” Energy Procedia 79, 520-527.

Jayathilake, R., and Rudra, S. (2017). “Numerical and experimental investigation of equivalence ratio (ER) and feedstock particle size on birchwood gasification,” Energies 10(8), article 1232. https://doi.org/10.3390/en10081232

Jia, X., Rui, N., Zhang, X., Hu, X., and Liu, C. (2019). “Ni/ZrO₂ by dielectric barrier discharge plasma decomposition with improved activity and enhanced coke resistance for CO methanation,” Catalysis Today 334, 215-222. https://doi.org/10.1016/j.cattod.2018.11.020

Katla-Milewska, D., Skorek-Osikowska, A., and Nazir, S. M. (2024). “Synthetic natural gas (SNG) production with higher carbon recovery from biomass: Techno-economic assessment,” Energy Conversion & Management 300, article 117895.
https://doi.org/10.1016/j.enconman.2023.117895

Koprivica, M., Petrović, J., Ercegović, M., Vukoje, M., Kukić, M., and Pap, S. (2024). “Improvement of combustible characteristics of Paulownia leaves via hydrothermal carbonization,” Biomass Conversion and Biorefinery 14, 3975-3985. https://doi.org/10.1007/s13399-022-02619-6

Kuhaudomlap, S., Srifa, A., Koo-Amornpattana, W., Fukuhara, C., and Ratchahat, S. (2024). “Insight and comprehensive study of Ni-based catalysts supported on various metal oxides for CO₂ methanation,” Scientific Reports 14, article 23149. https://doi.org/10.1038/s41598-024-73848-0

Li, J., Li, P., Li, J., Wang, X., Yu, H., and Tian, H. (2019). “Highly-dispersed Ni-NiO nanoparticles anchored on an SiO₂ support for an enhanced CO methanation performance,” Catalysts 9(6), article 506. https://doi.org/10.3390/catal9060506

Li, Y., Men, Y., Liu, S., Wang, J., Wang, K., Tang, Y., An, W., Pan, X., and Li, L. (2021). “Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition,” Applied Catalysis B: Environmental 293, article 120206. https://doi.org/10.1016/j.apcatb.2021.120206

Liu, Y., Zhu, L., Wang, X., Liu, H., Wang, Y., and Li, Y. (2017). “Catalytic methanation of syngas over Ni-based catalysts with different supports,” Chinese Journal of Chemical Engineering 25(5), 602-608. https://doi.org/10.1016/j.cjche.2016.10.019

Loweski Feliz, M., Abdelouahed, L., and Taouk, B. (2024). “Comparative and descriptive study of biomass gasification simulations using Aspen Plus,” Energies 17(17), article 4443. https://doi.org/10.3390/en17174443

Luo, S., Xiao, B., Hu, Z., Liu, S., Guan, Y., and Cai, L. (2009). “Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of temperature and steam on gasification performance,” International Journal of Hydrogen Energy 34(5), 2191-2194. https://doi.org/10.1016/j.ijhydene.2008.12.075

Lysne, A., Saxrud, I., Snidaro, R. L. G., and Blekkan, E. A. (2024). “Noble metal (Pt, Pd and Rh) promoted Ni-Co/Mg(Al)O catalysts for steam reforming of tar impurities from biomass gasification,” Journal of Catalysis 436, article 115567. https://doi.org/10.1016/j.jcat.2024.115567

Ma, L., Ma, H., Han, D., Wang, X., and Zhang, J. (2018). “Evolution of copper supported on Fe₃O₄ nanorods for WGS reaction,” Catalysts 8(10), article 415. https://doi.org/10.3390/catal8100415

Manatura, K., Lu, J.-H., Wu, K.-T., Hsu, H.-Y., and Wey, M.-Y. (2017). “Exergy analysis on torrefied rice husk pellet in fluidized bed gasification,” Applied Thermal Engineering 111, 1016-1024. https://doi.org/10.1016/j.applthermaleng.2016.09.135

Marcantonio, V., Müller, M., and Bocci, E. (2021). “A review of hot gas cleaning techniques for hydrogen chloride removal from biomass-derived syngas,” Energies 14(20), article 6519. https://doi.org/10.3390/en14206519

Matej, K., and Haydary, J. (2025). “Reduction of tar, sulfur, chlorine and CO2 in syngas produced by gasification of refuse-derived fuel pellets,” Scientific Reports 15, article 18446. https://doi.org/10.1038/s41598-025-03623-2

Matsumura, Y. (2002). “Evaluation of supercritical water gasification and biomethanation for wet biomass utilization in Japan,” Energy Conversion and Management 43(9-12), 1301-1310. https://doi.org/10.1016/S0196-8904(02)00016-X

Menin, L., Benedetti, V., Patuzzi, F., and Baratieri, M. (2023). “Techno-economic modeling of an integrated biomethane-biomethanol production process via biomass gasification, electrolysis, biomethanation, and catalytic methanol synthesis,” Biomass Conversion and Biorefinery 13, 977-998. https://doi.org/10.1007/s13399-020-01178-y

Miao, B., Ma, S. S. K., Wang, X., Su, H., and Chan, S. H. (2016). “Catalysis mechanisms of CO₂ and CO methanation,” Catalysis Science & Technology 6(12), 4048-4058. https://doi.org/10.1039/C6CY00478D

Mishra, S., and Upadhyay, R. K. (2021). “Review on biomass gasification: Gasifiers, gasifying mediums, and operational parameters,” Materials Science for Energy Technologies 4, 329-340. https://doi.org/10.1016/j.mset.2021.08.009

Niu, X., and Shen, L. (2022). “Evolution of carbon and nitrogen during chemical looping gasification of rapeseed cake with Ca-Fe oxygen carrier,” Chemical Engineering Journal 431, article 134232. https://doi.org/10.1016/j.cej.2021.134232

Omoregbe, O., Majewski, A. J., Steinberger-Wilckens, R., and Gadalla, M. (2023). “Investigating the effect of Ni loading on the performance of yttria-stabilised zirconia supported Ni catalyst during CO₂ methanation,” Methane 2(1), 86-102. https://doi.org/10.3390/methane2010007

Panagiotopoulou, P., Kondarides, D. I., and Verykios, X. E. (2008). “Selective methanation of CO over supported noble metal catalysts: Effects of the nature of the metallic phase on catalytic performance,” Applied Catalysis A: General 344(1-2), 45-54. https://doi.org/10.1016/j.apcata.2008.03.039

Peng, H., Cai, W., Huang, M., Xia, S., Zhu, L., Fang, X., and Ma, Z. (2025). “Advancing biomass gasification by the dry and wet torrefaction pretreatment,” Energy 324, article 136118. https://doi.org/10.1016/j.energy.2025.136118

Rahim, D. A., Fang, W., Wibowo, H., Ng, K. S., Lam, H. L., and Lim, J. S. (2023). “Review of high temperature H₂S removal from syngas: Perspectives on downstream process integration,” Chemical Engineering and Processing: Process Intensification 183, article 109258. https://doi.org/10.1016/j.cep.2022.109258

Reddy, S. N., Nanda, S., Dalai, A. K., and Kozinski, J. A. (2014). “Supercritical water gasification of biomass for hydrogen production,” International Journal of Hydrogen Energy 39(13), 6912-6926. https://doi.org/10.1016/j.ijhydene.2014.02.125

Rehling, B., Hofbauer, H., Rauch, R., Aichernig, C., and Tremmel, H. (2011). “BioSNG-process simulation and comparison with first results from a 1-MW demonstration plant,” Biomass Conversion and Biorefinery 1(2), 111-119. https://doi.org/10.1007/s13399-011-0013-3

Reid, W. V., Ali, M. K., and Field, C. B. (2020). “The future of bioenergy,” Global Change Biology 26(1), 274-286. https://doi.org/10.1111/gcb.14883

Ren, J., Liu, Y.-L., Zhao, X.-Y., Cao, J.-P., and Wei, X.-Y. (2020). “Methanation of syngas from biomass gasification: An overview,” International Journal of Hydrogen Energy 45(7), 4223-4243. https://doi.org/10.1016/j.ijhydene.2019.12.023

Rey, J. R. C., Longo, A., Rijo, B., Pinto, F., and André, R. (2024). “A review of cleaning technologies for biomass-derived syngas,” Fuel 377, article 132776. https://doi.org/10.1016/j.fuel.2024.132776

Romar, H., Tuomi, P., and Lassi, U. (2013). “Biomass gasification in an air-blown down-draft gasifier: Determination of tar compounds from producer gas,” BioResources 8(3), 3620-3629. https://doi.org/10.15376/biores.8.3.3620-3629

Rui, N., Zhang, X., Zhang, F., Liu, Z., Cao, X., Xie, Z., Zou, R., Senanayake, S. D., Yang, Y., Rodriguez, J. A., and Liu, C.-J. (2021). “Highly active Ni/CeO₂ catalyst for CO₂ methanation: Preparation and characterization,” Applied Catalysis B: Environmental 282, article 119581. https://doi.org/10.1016/j.apcatb.2020.119581

Sae-tang, N., Saconsint, S., Srifa, A., Koo-Amornpattana, W., Fukuhara, C., and Ratchahat, S. (2024). “Simultaneous production of syngas and carbon nanotubes from CO₂/CH₄ mixture over high-performance NiMo/MgO catalyst,” Scientific Reports 14, article 16282. https://doi.org/10.1038/s41598-024-66938-6

Safarian, S., Ebrahimi Saryazdi, S. M., Unnthorsson, R., Richter, C., and Haraldsson, H. H. (2021). “Gasification of woody biomasses and forestry residues: Simulation, performance analysis, and environmental impact,” Fermentation 7(2), article 61. https://doi.org/10.3390/fermentation7020061

Sánchez-Hervás, J., Ortiz, I., Martí, V., and Andray, A. (2023). “Removal of organic sulfur pollutants from gasification gases at intermediate temperature by means of a zinc-nickel-oxide sorbent for integration in biofuel production,” Catalysts 13(7), article 1089. https://doi.org/10.3390/catal13071089

Santana, H. E. P., Jesus, M., Santos, J., Rodrigues, A. C., Pires, P., Ruzene, D. S., Silva, I. P., and Silva, D. P. (2025). “Lignocellulosic biomass gasification: Perspectives, challenges, and methods for tar elimination,” Sustainability 17(5), article 1888. https://doi.org/10.3390/su17051888

Schmider, D., Maier, L., and Deutschmann, O. (2021). “Reaction kinetics of CO and CO₂ methanation over nickel,” Industrial & Engineering Chemistry Research 60(15), 5792-5805. https://doi.org/10.1021/acs.iecr.1c00389

Shayan, E., Zare, V., and Mirzaee, I. (2018). “Hydrogen production from biomass gasification: A theoretical comparison of using different gasification agents,” Energy Conversion and Management 159, 30-41. https://doi.org/10.1016/j.enconman.2017.12.096

Shen, Y. (2024). “Biomass pretreatment for steam gasification toward H₂-rich syngas production—An overview,” International Journal of Hydrogen Energy 66, 90-102. https://doi.org/10.1016/j.ijhydene.2024.04.096

Sikarwar, V. S., Zhao, M., Clough, P., Yao, J., Zhong, X., Memon, M. Z., Shah, N., Anthony, E. J., and Fennell, P. S. (2016). “An overview of advances in biomass gasification,” Energy & Environmental Science 9(10), 2939-2977. https://doi.org/10.1039/C6EE00935B

Suaad, A. Z., Ouadi, M., Mohammed, K., Al-Ansari, T., and Jahrami, H. (2025). “Simulation of biomass gasification and syngas methanation for methane production with H₂/CO ratio adjustment in Aspen Plus,” Energies 18(16), article 4319. https://doi.org/10.3390/en18164319

Taba, L. E., Irfan, M. F., Daud, W. M. A. W., and Chakrabarti, M. H. (2012). “The effect of temperature on various parameters in coal, biomass and CO-gasification: A review,” Renewable and Sustainable Energy Reviews 16(8), 5584-5596. https://doi.org/10.1016/j.rser.2012.06.015

Tao, M., Zhou, C., Shi, Y., Li, Y., Wang, H., and Zhang, J. (2020). “Enhanced sintering resistance of bimetal/SBA-15 catalysts with promising activity under a low temperature for CO methanation,” RSC Advances 10(35), 20852-20861. https://doi.org/10.1039/D0RA02168G

Tiwari, R., Sarkar, B., Tiwari, R., Pendem, C., Sasaki, T., and Bal, R. (2014). “Pt nanoparticles with tuneable size supported on nanocrystalline ceria for the low temperature water-gas-shift (WGS) reaction,” Journal of Molecular Catalysis A: Chemical 395, 117-123. https://doi.org/10.1016/j.molcata.2014.08.021

Valizadeh, S., Hakimian, H., Farooq, A., Jeon, B.-H., and Kim, H.-T. (2022). “Valorization of biomass through gasification for green hydrogen generation: A comprehensive review,” Bioresource Technology 365, article 128143. https://doi.org/10.1016/j.biortech.2022.128143

Vieira, L. H., Ferreira, L. F., Rasteiro, C. S. S., Madeira, L. M., and Ribeiro, A. M. (2023). “Noble metals in recent developments of heterogeneous catalysts for CO₂ conversion processes,” ChemCatChem 15(19), article e202300493. https://doi.org/10.1002/cctc.202300493

Wagner, H., Wulf, C., and Kaltschmitt, M. (2015). “Polygeneration of SNG, heat and power based on biomass gasification and water electrolysis-concepts and their assessment,” Biomass Conversion & Biorefinery 5(1), 103-114. https://doi.org/10.1007/s13399-014-0127-5

Wang, K., Kong, G., Zhang, G., Liu, D., Wang, X., and Yang, Y. (2022). “Steam gasification of torrefied/carbonized wheat straw for H₂-enriched syngas production and tar reduction,” International Journal of Environmental Research and Public Health 19(17), article 10475. https://doi.org/10.3390/ijerph191710475

Wang, T., Tang, R., and Li, Z. (2024). “Enhanced CO₂ methanation activity over Ni/CeO₂ catalyst by adjusting metal-support interactions,” Molecular Catalysis 558, article 114034. https://doi.org/10.1016/j.mcat.2024.114034

Wang, W., Li, X., Zhang, Y., Zhang, Z., Tan, Y., and Han, Y. (2017). “Strong metal-support interactions between Ni and ZnO particles and their effect on the methanation performance of Ni/ZnO,” Catalysis Science & Technology 7(19), 4413-4421. https://doi.org/10.1039/C7CY01119A

Wongsiriamnuay, T., Kannang, N., and Tippayawong, N. (2013). “Effect of operating conditions on catalytic gasification of bamboo in a fluidized bed,” International Journal of Chemical Engineering 2013, article 297941. https://doi.org/10.1155/2013/297941

Xiao, Y.-S., Song, Y.-H., Liu, C., Wang, Y., Zhang, J., and Wei, Y. (2020). “Balancing free and confined metallic Ni for an active and stable catalyst—A case study of CO methanation over Ni/Ni-Al₂O₃,” Journal of Energy Chemistry 50, 73-84. https://doi.org/10.1016/j.jechem.2020.02.053

Xing, W., Liu, Y., Zhang, W., Li, X., Wang, C., and Chen, H. (2020). “Study on methanation performance of biomass gasification syngas based on a Ni/Al₂O₃ monolithic catalyst,” ACS Omega 5(44), 28597-28605. https://doi.org/10.1021/acsomega.0c03536

Ye, R., Ma, L., Hong, X., Wang, X., Fan, X., and Gong, J. (2024). “Boosting low-temperature CO₂ hydrogenation over Ni-based catalysts by tuning strong metal-support interactions,” Angewandte Chemie International Edition 63(3), e202317669. https://doi.org/10.1002/anie.202317669

Ye, R.-P., Liao, L., Reina, T. R., Liu, J., Zheng, Y., Chen, M., and Fan, X. (2021). “Engineering Ni/SiO₂ catalysts for enhanced CO₂ methanation,” Fuel 285, article 119151. https://doi.org/10.1016/j.fuel.2020.119151

Yu, J., Feng, B., Liu, S., Wang, H., Li, Y., and Zhang, X. (2022). “Highly active Ni/Al₂O₃ catalyst for CO₂ methanation by the decomposition of Ni-MOF@Al2O3 precursor via cold plasma,” Applied Energy 315, article 119036. https://doi.org/10.1016/j.apenergy.2022.119036

Zhang, P.-D., Yang, Y.-L., Jin, S., Zheng, Y.-H., and Wang, L.-S. (2009). “Opportunities and challenges for renewable energy policy in China,” Renewable and Sustainable Energy Reviews 13(2), 439-449. https://doi.org/10.1016/j.rser.2007.11.005

Zhang, S., Wang, J., Ye, L., Liu, X., Chen, H., and Zhao, Y. (2023). “Investigation into biochar supported Fe-Mo carbides catalysts for efficient biomass gasification tar cracking,” Chemical Engineering Journal 454, article 140072. https://doi.org/10.1016/j.cej.2022.140072

Zhang, T., Ai, H., and Liu, Q. (2019). “La₂O₃-promoted Ni/Al₂O₃ catalyst for CO methanation: Enhanced catalytic activity and stability,” Energy Technology 7(11), article 1900531. https://doi.org/10.1002/ente.201900531

Zhang, Y., Yang, H., Liu, Q., Ai, H., and Liu, Z. (2020). “MoOx-doped ordered mesoporous Ni/Al₂O₃ catalyst for CO methanation,” Energy Technology 8(6), article 2000165. https://doi.org/10.1002/ente.202000165

Zhao, B., Liu, P., Li, S., Wang, X., Zhang, Y., and Han, Y. (2020). “Bimetallic Ni-Co nanoparticles on SiO₂ as robust catalyst for CO methanation: Effect of homogeneity of Ni-Co alloy,” Applied Catalysis B: Environmental 278, article 119307. https://doi.org/10.1016/j.apcatb.2020.119307

Zhao, L., Qi, Y., Song, L., Wang, X., Zheng, X., and Chen, H. (2019). “Solar-driven water-gas shift reaction over CuOx/Al₂O₃ with 1.1% of light-to-energy storage,” Angewandte Chemie 131(23), 7790-7794. https://doi.org/10.1002/ange.201902324

Zhu, M., Wang, Q., and Wang, S. (2025). “Recent advances and future perspectives in catalyst development for efficient and sustainable biomass gasification: A comprehensive review,” Sustainability 17(16), article 7370. https://doi.org/10.3390/su17167370

Article submitted: May 21, 2026; Peer review completed: July 28, 2026; Revised version received and accepted: August 12, 2026; Published: September 16, 2026.

DOI: 10.15376/biores.21.4.Wang