Life cycle water footprint and carbon footprint analysis of municipal sludge plasma gasification process

Abstract

In this study, the life cycle carbon footprint and water footprint of municipal sludge-to-hydrogen conversion by plasma gasification were analyzed. Results show that the carbon footprint of the process is 950 kg/GJ, and the water footprint is 3.21 m3/GJ in the basic scenario. The carbon footprint of the Rectisol units was the highest, accounting for 24.04%. Low-pressure nitrogen can be used for acid gas desorption to reduce carbon emissions. The life cycle water consumption comes mainly from electricity consumption (1.93 m3/GJ) and the cooling process (0.610 m3/GJ). Optimizing the electricity structure reduces the water footprint. The effects of 24 scenarios were investigated using sensitivity analysis. It was found that improving hydrogen efficiency or reducing electricity consumption can improve environmental performance. In addition, regional differences in the electricity structure can lead to differences in results. The carbon footprint of hydro-dominated regions (Sichuan, Qinghai, Tibet, and Yunnan) was only 20% of the basic scenario, while the water footprint was approximately threefold. This work presents the values of carbon emissions and water consumption within the specific scenario of municipal sludge-to-hydrogen by the plasma gasification process, providing support for its further development.