Low grade ores – Smelt, leach or concentrate?

Metallic ore grades are falling globally as the higher grade reserves are exploited first and are progressively depleted. At the same time, the demand for primary metals extracted from these ores is expected to increase, despite increased levels of dematerialisation and recycling. Sustainability concerns have highlighted the need to meet these demands while at the same time minimising resource consumption and environmental emissions. A study was therefore undertaken using life cycle assessment methodology to examine various alternative processing routes for extracting metal from low grade ores (down to 0.1% metal), particularly those of copper and nickel, in terms of their life cycle-based energy consumption (embodied energy) and greenhouse gas emissions. The processing routes examined included conventional concentrating and smelting, direct ore smelting, heap leaching, pressure leaching and in situ leaching. This paper presents the results of this study.