in other cases discrepancies may be due to different lca databases being utilized or arise as a result of different assumptions being made regarding material types such as steel alloys in the face of uncertainty of the exact types of materials used in each component this creates uncertainty which we illustrate here using a simple calculation exercise in one study burger and bauer ferrous metal content in the kw onshore wind turbine excluding the foundation consists of per cent cast iron per cent lowalloy steel and per cent highalloy chromium steel while in a second study martinez et al