Comparative Assessment of Hydrothermal Gasification and Anaerobic Digestion using Aspen Plus and SuperPro

Wet biomass is gaining increasing attention as an energy source globally. Various wet biomass materials like macroalgae, microalgae, sewage sludge, cattle manures, and food waste, are of high moisture contents, typically around 70% or more. There are two routes of high potential for converting these wet biomasss resoures to gaeous fuel, which are biomethanation and supercritical water gasification (SCWG). Biomethanation is conversion of wet-organic residues to biogas using via anaerobic digestion process. SCWG is a thermochemical conversion process, taking place in supercritical water producing enriched CH4 and H2 gases. In this study, the two processes are comperatively investigated using different process simulation softwares. Aspen Plus was employed for SCWG, while the biomethanation process was simulated with SuperPro. Various raw materials were used as input. We calculated the energy efficiency of the biomethanation process using experimental yields from the literature. For the SCWG process, we determined the higher heating value based on the simulated composition of the methane-enriched gas. Additionally, we conducted an economic analysis to compare the two processes, taking into consideration specific criteria relevant to the Norwegian context.