## 3 Results and Discussion
### LCA of Hydrogen Production
#### 3.1.2 Agricultural Residue Gasification  
Figure 6 illustrates the environmental profile of hydrogen (H\({}_{2}\)) production via agricultural residue gasification, showing a global warming potential (GWP) of 1.30 kg CO\({}_{2}\)-eq/kg H\({}_{2}\), which is 4.89 times lower than that of biogas reforming. This significant reduction aligns with [PERSON] et al. (2009) [51], who attributed such outcomes to the carbon-neutral nature of biomass feedstocks, which offset process-related emissions. However, ozone depletion (2.14 \(\times\) 10\({}^{-5}\) kg CFC11-eq) and ionizing radiation (\(-\)0.0355 kBq Co-60-eq) remain notable, driven by reliance on grid electricity, a trend also observed in electrolysis systems ([PERSON] et al., 2019) [47]. Freshwater eutrophication (0.0005 kg P-eq) and marine ecotoxicity (0.15 kg 1,4-DCB-eq) are linked to nitrogen fertilizer use and ash emissions, mirroring [PERSON] et al. (2017) [48], who emphasized nutrient runoff as a systemic issue in biomass-based systems. The mineral resource scarcity value (0.0106 kg Cu-eq) reflects the material demands associated with zinc oxide and solid manure usage. Water consumption (5.37 m\({}^{3}\)/kg H\({}_{2}\)), while higher than biogas reforming, remains lower than that of fossil-based methods, though advanced dry gasification technologies could further reduce this. Overall, gasification's lower GWP and fossil resource depletion (3.20 vs. 10.42 kg oil-eq) position it as a promising low-carbon pathway, contingent on renewable energy integration and optimized feedstock management to address trade-offs in water use and material efficiency. Figure 6 also shows that \"electricity and medium-voltage\" yields negative environmental impacts across all categories, while \"manure\" contributes to negative values, specifically in the ionizing radiation category. These negative values indicate environmental credits resulting from coproduct advantages and the avoidance of certain processes. The gasification system generates excess electricity that substitutes conventional grid electricity, typically sourced from fossil fuels or nuclear energy, thus mitigating impacts like greenhouse gas emissions and ionizing radiation. The utilization of solid manure as feedstock mitigates emissions associated with conventional disposal methods and decreases dependence on energy-intensive inputs, such as synthetic fertilizers. These contributions illustrate the potential of renewable feedstocks and energy recovery to improve the environmental performance of hydrogen production. However, some inputs still exert environmental burdens due to the resource use and emissions generated during their production, transportation, or utilization within the gasification system. The Cumulative Energy Demand (CED) and Non-Renewable Energy (NRE) use are critical indicators of hydrogen production systems' energy intensity and sustainability. The CED represents the total amount of primary energy consumed throughout a product's life cycle--including both renewable and non-renewable sources--while NRE accounts only for the fraction derived from fossil-based and nuclear sources. The CED is typically calculated using Equation (9):  
\[\text{CED}=\sum_{i=1}^{n}(E_{i}\times EF_{i}) \tag{9}\]  
where \(E_{i}\) is the quantity of input \(i\) (e.g., electricity, diesel) and \(EF_{i}\) is its energy factor in MJ/unit. For NRE, the non-renewable share of total energy is calculated using Equation (10):  
\[\text{NRE}=\sum_{j=1}^{m}(E_{j}\times EF_{j})_{\text{non-renewable}} \tag{10}\]  
where \(E_{j}\) represents the quantity of input j that is non-renewable (e.g., coal, natural gas, diesel). \(EF_{j}\) is the energy factor of non-renewable input j expressed in MJ per unit of the input. In this study, biogas reforming consumed a higher CED of approximately 1.95 MJ/kg H\({}_{2}\), primarily due to the electricity demand during the anaerobic digestion and reforming stages, with most energy sourced from the fossil-fueled grid.