Temporal and regional variability in the technological characteristics of primary aluminum smelters affect life cycle greenhouse gas (GHG) emissions embodied not only in the production but also the trade and consumption of primary ingot. Existing life cycle inventory (LCI) reports and databases however provide limited detail on the impacts of these sources variation. LCI data are updated every few years and typically report a single global average GHG intensity of primary ingot production. With primary aluminum ingot being a globally-traded commodity the variation in life cycle GHG emissions may have implications for carbon leakage in the event of unilateral carbon regulation and the use of aluminum for product lightweighting.
A life cycle GHG emissions model is developed with the objective of quantifying the emissions embodied in the production trade and consumption of primary aluminum ingot in six world regions (Africa North America South America Asia Europe and Oceania) from 1990 to 2005. This dynamic model calculates emissions time series based on annual data for smelter electricity consumption electricity fuel mix carbon intensity of fossil fuel electricity generation and perfluorocarbon (PFC) emissions. Bilateral primary ingot trade data are used to calculate the GHG emissions embodied in imports exports and consumption.
Model results indicate that the production of primary aluminum ingot accounted for approximately 0.78% and 0.93% of global GHG emissions in 1990 and 2004 respectively. Most regions exhibited an increase in absolute GHG emissions over the period with the largest increase occurring in Asia. Concurrently efficiency improvements and PFC reduction programs have led to a decline in GHG emissions intensity of production for many of the regions. Analysis reveals that GHG emissions embodied in primary ingot trade constitute a significant fraction of the emissions associated with primary ingot for Africa Asia Latin America and Oceania.