The goal of this project is to determine the reductions in greenhouse gas (GHG) emissions associated with the recycling of aerospace alloys. This study is based on an aerospace recycler that sells much of its high-performance alloy scrap directly to remelters that produce these alloys for aircraft engine component manufacturers, with significant potential environmental benefits arising from the substitution of recycled materials for virgin materials. The project team explored existing sources of environmental data for all of the metals that make up aerospace alloys, and ten common alloys were chosen as case studies. Certain metal elements, including niobium, rhenium, tungsten, and zirconium, did not have any robust environmental impact information, and for these GHG emissions factors from primary production were modeled using a variety of statistical and industrial data sources. The project team then investigated the forms of metal inputs into alloying operations to ensure that the model reflects actual industrial practices and that the alloy scrap substitutes for virgin materials. GHG emissions are also incurred through alloy scrap collection and processing, and so a carbon footprint was performed for alloy recycling operations in order to determine these burdens. Overall, the recycling of aerospace alloys for reuse in the aerospace industry represents significant reductions in GHG emissions for each of the ten alloys considered, while emissions associated with collection and processing are <5% in comparison. Certain elements occur in small quantities in aerospace alloys, such as rhenium (Re) and tantalum (Ta), but due to their high carbon intensity they significantly influence the final results.

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