## 1 Introduction
Methane decomposition: Methane breaks down into hydrogen gas and solid carbon (graphite), with an enthalpy change of +74.85 kJ/mol (Equation (6)):  
\[\mathrm{CH_{4}}\ \leftrightarrow\mathrm{2H_{2}}+\mathrm{C_{(graphite)}\ \Delta H_{298K}^{\circ}=+74.85 kJ/mol} \tag{6}\]  
CO reduction reaction: Carbon monoxide reacts with steam to form solid carbon (graphite), hydrogen gas, and carbon dioxide, releasing \(-131.26\) kJ/mol of energy (Equation (7)):  
\[\mathrm{CO+H_{2}O\ \leftrightarrow C_{(graphite)}+H_{2}+CO_{2}\ \Delta H_{298K}^{\circ}=-131.26 kJ/mol} \tag{7}\]  
Finally, hydrogen purification can be performed by CO2 removal via pressure swing adsorption, chemical absorption, and methanation, or metallic membrane separation. Biomass gasification (see Figure 2) presents a promising approach for generating hydrogen-rich synthetic gas (syngas), which can subsequently be refined to yield pure hydrogen [22; 23]. Gasification benefits from the carbon neutrality of biomass, where CO2 emissions are offset by the carbon absorbed during plant growth. Gasification operates under sub-stoichiometric conditions, typically within an equivalence ratio (ER) range of 0.20 to 0.45. The yield and composition of syngas depend on several variables, including the feedstock type, reactor design, and nature of gasifying agents, such as air, oxygen-enriched air, CO2, or steam [24]. Biomass gasification is gaining attention due to its adaptability in processing diverse feedstocks, including agricultural residues, wood waste, and refuse-derived fuels [25]. The environmental impact of gasification varies depending on feedstock characteristics, operational conditions, and pretreatment requirements [26; 27]. LCA is a widely adopted methodology for evaluating potential environmental impacts and resource use throughout a product or system's entire life cycle, from raw material extraction to end-of-life stages, as defined by SETAC and standardized under ISO 14040 [23]. Each stage of production, use, and disposal carries specific environmental implications, which are thoroughly captured by the LCA framework [12]. LCA helps enhance resource efficiency and identify potential environmental trade-offs, supporting informed policy development in the energy sector. The LCA method has been widely utilized in recent years to evaluate the environmental performance of bioenergy processes [28; 29]. In reviewing the methodological aspects of the selected life cycle assessment (LCA) studies, several key software tools and approaches were identified, each offering distinct advantages and  
Figure 2: Biomass steam gasification plant design [24]. limitations. SimaPro, OpenLCA, and GaBi emerged as the most widely used LCA software platforms. SimaPro is renowned for its robustness and compatibility with a broad range of LCIA methods and the ecoinvent database, making it ideal for both academic and industrial research; however, it requires a paid license and has a steep learning curve. OpenLCA, in contrast, is open-source and user-friendly, allowing flexible modeling and integration with non-proprietary databases, though it may lack some advanced features and data compatibility. GaBi excels in industrial applications and offers high-quality proprietary datasets, especially for European contexts, but its limited transparency and licensing costs can pose challenges. The reviewed studies utilized a mix of data types, secondary data, software simulations, and, in some cases, primary measurements. The background databases varied, with ecoinvent being the most common due to its comprehensive coverage and standardized structure, although different versions (e.g., 3.1 to 3.8) may influence consistency. GREET and the GaBi database were also used, offering advantages for regional specificity and industrial data, but they are limited in scope or accessibility. Table 1 presents the methodological frameworks used in the studies reviewed, highlighting key parameters such as LCA software, data types, background databases, functional units (F.Us. ), system boundaries, and LCIA methods.