On the green hydrogen production through gasification processes: A techno-economic approach

Abstract

Green hydrogen rises in the world energy scenario as one of the most promising non-carbon-based fuels capable of replacing fossil fuels. Biomass gasification is emerging as a cleaner and sustainable process of producing green hydrogen. Green hydrogen can be obtained by resorting to different biomass gasification processes. Moreover, techno-economic studies are essential to determining the viability of these processes and are missing in the literature. The novelty of this study is the identification of the gasification process that produces the highest hydrogen yields and the presentation of the viability conditions for three gasification plants aiming to produce green hydrogen. The methodology followed is based on the development of three models of biomass gasification processes (conventional, plasma, and supercritical water) in Aspen Plus® to estimate maximum hydrogen yields through a parametric study. The economic study was conducted based on economic indicators (net present value and payback) to assess the viability of each gasification process for green hydrogen production. The results suggest that supercritical water gasification is the most suitable process for hydrogen production, with hydrogen yields of 0.844 Nm3/kgbiomass. Hydrogen yields of 0.828 Nm3/kgbiomass, and 0.758 Nm3/kgbiomass were achieved for the conventional gasification and plasma gasification processes, respectively. From the economic assessment, it was concluded that none of the gasification processes are viable under the determined optimal operating conditions. A sensitivity analysis, however, revealed that conventional gasification is viable for steam-to-biomass ratios <3. Process intensification techniques were applied, revealing that supercritical water gasification can be viable for feed concentrations between 15 and 25%. A minimum selling price of 7 €/kg, 10 €/kg, and 13 €/kg were obtained for green hydrogen generated by the conventional, supercritical water, and plasma gasification processes, respectively. The results obtained in this study are of paramount importance for the hydrogen economy. However, this research should be supplemented by further intensifying the gasification processes in order to bring green hydrogen production costs down to a more competitive level.