Regional-level analysis for the material flows and process energy demands of aluminum and steel in the American automotive industry
This study details the development of a method and framework for regionally linked, sector-specific material flow analysis (MFA) models and presents the results of such models for aluminum and steel entering the American automotive industry (henceforth termed automotive aluminum and automotive steel). Additionally, the models facilitate a regionalized perspective of the process energy demands associated with automotive aluminum and steel, including their respective raw materials.
For automotive aluminum in 2016, the mass flows of mill products (sheet and extrusions) are sorted by North American Electric Reliability Corporation (NERC) regions if originating from the USA and Canadian provincial region if originating from Canada. Mass flows unable to be distinguished into such categories were aggregated into a regionally unresolved Local region with boundaries of the USA and Canada. Major mill product mass flow regions include NPCC (23%), SERC (20%), MRO (18%), RFC (13%), and Local (18%). Of the primary aluminum entering the American automotive industry, 94% is sourced from within the USA and Canada, with Quebec accounting for nearly 70% of the primary aluminum supply. Aluminum scrap flows entering the American automotive industry were determined to be out of the scope of this study and not regionally analyzed. Upstream of primary aluminum, the alumina entering the American automotive industry is largely internationally sourced (91%). Further upstream, bauxite is completely internationally sourced. Both materials come primarily from the southern hemisphere. Considering the entire production cycle of automotive aluminum, from bauxite to mill product, the regional distribution of the total process energy demand embodied in automotive aluminum is largely influenced by the regional distribution of primary aluminum. This highlights the significant energy, particularly electricity, required for primary aluminum production and its dominance of energy demand in automotive aluminum’s production cycle.
Analyzing automotive steel in 2017, the large majority of automotive steel mill product comes from the RFC (63%) and SERC (20%) NERC regions, with only Canada and Turkey contributing over one percent of the overall mass flow. The same regional dominance by the RFC and SERC regions is observed for crude steel that enters the American automotive industry. RFC processes 69% of the crude steel supply by mass while SERC processes 7%. The regional distributions of coke, coking coal, iron ore, lime, and steel scrap exhibit the dominance of the USA in supplying these raw materials for automotive steel. Coke is primarily sourced from the RFC (67%) and SERC (10%) regions in large part because those are the regions where most crude steel is produced in the USA. Conversely, the majority of direct reduced iron (DRI) and pig iron used for automotive steel is internationally sourced. SERC represents 24% and TRE 16% of the total DRI supply for automotive steel, but international sources constitute 56% of the total, with Trinidad and Tobago alone supplying 30%. The pig iron supply for automotive steel is heavily dominated by international sources, with Russia (38%), Ukraine (16%), and Brazil (16%) supplying the largest fractions. Although the total process energy demand for automotive steel is dominated by the USA (75%) and especially the RFC (54%) and SERC (10%) regions, large international sourcing of energy intensive DRI and pig iron brings down the USA’s overall share in total process energy demand compared to its share in total mass of material products supplied.
The results from applying this method to automotive aluminum and steel may be used to help inform the sustainability of the American automotive, aluminum, and steel industries and integrated into future automotive centric life cycle assessment (LCA) models to provide more geographically specific energy demand data.