Assessment of supercritical water gasification process for combustible gas production from thermodynamic, environmental and techno-economic perspectives: A review

Supercritical water gasification (SCWG) technology is an effective gasification technology without the energy intensive drying process, especially for feedstocks with high water content. In this paper, energy and exergy efficiencies, thermodynamic equilibrium, life cycle assessment (LCA), and economic costs for combustible gas production in various SCWG systems are investigated and summarized. Through sensitivity analysis, the effects of operating parameters including temperature, pressure, concentration, oxidant addition, residence time, system scale, and heating mode on the SCWG process are analyzed to optimize the SCWG process from the perspectives of thermodynamics, environmental and economic performance. Additionally, the environmental impact and economic costs of SCWG technology are compared with those of other hydrogen production technologies to ascertain the feasibility of its large-scale application. In terms of the average global warming potential (GWP) and acidification potential (AP) generated from various hydrogen production technologies, the environmental competitiveness of SCWG is significantly higher than steam reforming and auto-thermal reforming, but inferior to water electrolysis, water-splitting, and conventional gasification technologies. The techno-economic analysis results show that the average hydrogen production cost (HPC) of SCWG technology is lower than that of conventional biomass gasification, steam reforming, water electrolysis, and thermochemical hybrid sulfur cycle, slightly higher than that of pyrolysis, thermochemical S-I water-splitting cycle and Cu-Cl water-splitting cycle. This review is expected to guide future research on the optimization of the SCWG process from the aspects of thermodynamic, environmental, and economic analysis.