Life cycle assessment of a process integrating supercritical water gasification with direct reduced iron production

Finding alternative technologies to reduce carbon emissions of the steel industry has become a pressing concern. Supercritical water gasification (SCWG) combined with Hydrogen Production-Shaft furnace-Electric arc furnace (HSE) process offers a promising low-carbon alternative. The proposed route converts biomass to biosyngas through SCWG technology to produce direct reduced iron, followed by an electric arc furnace process to produce crude steel. In this study, the environmental impact of the SCWG-HSE process was evaluated using life cycle assessment (LCA). LCA was conducted using the Gabi V9.2 software, and the Ecoinvent 3.6 database within the program. It was found that the SCWG-HSE process has a 61 % lower global warming potential compared to the conventional BF-BOF process, and a 28 %–30 % reduction compared to the Coal gasification- HSE and Natural gas based- HSE processes. It is comparable to the renewable hydrogen-based HSE route. The cradle-to-gate global warming potential of the proposed system is estimated to be 803 kg CO₂ eq./t crude steel. In the process, the hydrogen production and electric arc furnace segments are the main sources of global warming potential. Further analysis shows that an additional global warming potential reduction of about 38 % can be achieved by integrating Carbon Capture and Storage technologies, while optimization of the electricity supply structure is expected to achieve a global warming potential reduction of up to 63 %. This study is not limited to assessing global warming potential, but also covers other environmental impact indicators. The results show that the SCWG-HSE process has significant potential in terms of environmental performance.