From excavated waste to hydrogen: Life cycle techno-environmental-economic comparison between plasma-gasification-based water gas shift and sorption enhanced water gas shift routes

Abstract

The mismanagement of excavated waste (EW) is leading to serious land occupancy and greenhouse gases leakage problems globally. This study explores the possibility to realize utilization of EW and satisfaction of the hydrogen fuel demand at the same time. Based on plasma gasification (PG), the excavated waste has shown its potential to act as a sustainable source of hydrogen. In this study, the techno-environmental-economic performance of the EWtH (excavated waste to hydrogen) process based on PG-WGS-AGR (water gas shift-acid gas removal) and PG-SEWGS (sorption enhanced water gas shift) routes are investigated. The results demonstrate that the EWtH process based on the PG-SEWGS route has higher exergy efficiency, better environmental performance, and more promising economic feasibility. The EWtH process can maintain profitable when resisting the fluctuation of EW treatment subsidy, selling price of CO2 and carbon tax (±75%), with the biggest LPEW (levelized profit of excavated waste) drop of 19.22%. However, as the selling of H2 is the largest income, the LPEW has decreased to a negative value within the fluctuation of the selling price of H2 in ± 55%, which suggests that the selling price of H2 is the decisive factor in the economic feasibility of the EWtH process. Also, the EW with fewer landfill years brings higher profit, and the material recovery process plays a more significant role in the treatment of EW with longer landfill years. The highest exergy efficiency (57.79%) and the most environmentally friendly performance (-70.84 mPE) locates in the 05-EWtH process applying SEWGS, and the 15-EWtH process based on PG-SEWGS route has the highest LPEW of 185.78 $/tonEW.