The use of LCA for the environmental evaluation of the recycling of galvanized steel

Abstract: The goal for this project was to build and spread knowledge about the use of LCA in the metallurgical industry, as well as to evaluate the use of LCA within the metallurgical industry in general, particularly for the management of waste- and by-products. For this, the assessment of the recycling of zinc coated scrap to an electric arc furnace was considered as a suitable case study. Zinc can be recovered directly from the scrap by de-zincing or from the dust generated in the furnace when the scrap is remelted. A number of hypothetical process routes involving dezincing as well as four different dust treatment processes were constructed. The environmental effects of the various process routes were studied by using LCA methods. The processes were evaluated on the basis of greenhouse and acidification potential as well as consumption of zinc resources. The results showed that while recycling of zinc saves natural resources, the potential effect on climate changes and acidification does not necessarily decrease. The two latter impact categories are tightly connected to the consumption of energy in the processes. The major part of the energy in the production of zinc from primary as well as secondary raw materials is consumed in the reduction of ZnO to zinc. The energy saving potential is thus relatively small.