Exergy cost allocation of by-products in the mining and metallurgical industry

Abstract

In the mining and metallurgical industry, with each ore, products, by-products and wastes appear. Allocations among products when one or more by-products come about in a mining or metallurgical process are based either on tonnage or on commercial prices. Both ways of allocating costs entails disadvantages that are analysed in this paper. Besides a rigorous way to allocate costs among non-fuel minerals through the exergy replacement costs is proposed. Particularly, 33 different mineral deposit models where 12 coupled products are obtained have been analysed. Results show that the average difference between the economic approach and the exergy approach range from 0% to 30%. The highest difference is presented in metals such as copper, nickel and cobalt. Therefore, as a case study, exergy cost allocation was applied to copper and nickel production with its respective by-product (cobalt). The results suggest that if exergy replacement cost is applied, cost allocation values are similar to those obtained via the price indicator. This supports the idea that the exergy replacement cost is very close to the value society places on minerals. That said, contrarily to prices, exergy replacement cost does not fluctuate with external factors linked to market mechanisms but remains constant.