Estimation of greenhouse gas emissions from ferroalloy production using life cycle assessment with particular reference to Australia

Ferroalloys are defined as iron-bearing alloys with a high proportion of one or more other elements – manganese, chromium, silicon, molybdenum, etc., mainly used by the iron and steel industries. Life cycle assessment methodology was used to estimate the greenhouse gas (GHG) footprint of a number of these ferroalloy production processes. The results of the study showed that GHG footprint for ferroalloy production in Australia was 1.8 t CO2e/t FeMn, 2.8 t CO2e/t SiMn and 3.4 t CO2e/t FeSi alloy metal. These results compare with GHG footprints for ferronickel and ferrochromium of 13.9 t CO2e/t and 3.0 t CO2e/t, respectively revised from an earlier study. These GHG footprint estimates were calculated using the Tasmanian electricity greenhouse gas emission factor since these ferroalloy industries are located in Tasmania, Australia. The major difference in greenhouse gas emissions between the various ferroalloys is largely due to their respective amounts of electricity use and coke/coal consumption. These results are not too different to the results from a limited number of studies reported in the literature when compared on a similar electricity source basis. The LCA results also showed that coke and coal usage contributed close to 60% or more of the total GHG emissions from the various ferroalloy production processes. In light of this finding, there would appear to be an opportunity to reduce GHG emissions from ferroalloy production if fossil fuel-based coal is replaced with biomass based renewable carbon.