Life cycle assessment of methanol production by a carbon capture and utilization technology applied to steel mill gases

The iron and steel industry is responsible for a significant amount of direct and indirect greenhouse gas emissions. The goal of this study is to evaluate the environmental impacts of a new system in which the steel mill gases (Basic oxygen furnace gases BOFGs, Blast furnace gases BFGs, and Coke oven gases COGs) are used to produce both methanol and electricity. In the specific configuration under study, 100% of BOFGs and 90% of COGs are used for methanol production, whereas 100% of BFGs and 10% COGs are used for electricity production. The analysis was conducted by applying the Life Cycle Assessment methodology. The model considered all the processes associated with the treatment of the gases, including the methanol and electricity productions and the corresponding avoided products. The results show that for most of the impact categories (12 out of 17), the benefits associated with the avoided productions are higher than the impacts caused by the process itself. In particular, the avoided methanol gives an important benefit in four impact categories. Focusing on the contributions adding impacts to the environment, the power plant and the chemicals used in some of the units resulted as the most important ones. When considering the use of the methanol as ship fuel in substitution of heavy fuel oil, the avoided impacts are higher than the impacts associated with the process itself for 15 out of the 17 impact categories, and the impact on climate change is reduced from 504 kgCO2eq of the baseline scenario to 491 kgCO2eq per 1000 kg steel mill gases.