Substitution of Fossil Coal with Hydrochar from Agricultural Waste in the Electric Arc Furnace Steel Industry: A Comprehensive Life Cycle Analysis

The iron and steel industry remains one of the most energy-intensive activities with high CO2 emissions. Generally, the use of fossil coal as chemical energy in an electric arc furnace (EAF) makes up 40-70% of the total direct emissions in this steelmaking process. Therefore, substituting conventional fossil fuels with alternatives is an attractive option for reducing CO2 emissions. In this study, the environmental impacts of EAF-produced steel were comprehensively assessed using pulverized hydrochar as the charged and injected material as a replacement for fossil coal. An environmental analysis was performed based on the LCA methodology according to the framework of ISO 14044. This study evaluated two different outlines: the use of fossil coal and its replacement with hydrochar from the winemaking industry as a carbon source in the EAF steelmaking process. The environmental impacts from the manufacturing of the hydrochar were calculated using different scenarios, including novel industrial ways to use vinasse as a moisture source for the co-hydrothermal carbonization of vine pruning and exhausted grape marc (EGM). The environmental impacts per unit of steel were reported as a function of the ratio between the fixed carbon of the injected material and the material amount itself. The results highlight the sustainability of the hydrothermal carbonization process and the use of the hydrochar in EAF steelmaking. Moreover, the electricity mix used for the EAF process has significant relevance. The main outline of the results might assist decision-makers to determine which technological route is most likely to be effective in reducing future CO2 emissions from the iron and steel industry.