A big share of ferro nickel for the stainless steel industry is coming from nickel pig iron (NPI). There is no environmental data on the different production routes of NPI in the public domain. This chapter will show how environmental impact (here global warming potential [GWP]) can be calculated using basic technical data for processes like rotary kiln, electric arc furnaces, or blast furnaces. These basic data are modelled in the thermodynamic modelling software HSC 9.1 where pyrometallurgical processes can be simulated. The resulting consumption data for the different processes are then transferred to the life cycle assessment (LCA) for Expert Software from Sphera where the GWP is calculated.