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:: Environmental Assessment of Emissions from Mining and Processing
The loading and hauling operations necessary for getting iron ore and bauxite from deposits to mineral processing facilities makes the biggest contribution to greenhouse gas emissions over the mining and mineral processing stages, environmental assessments of both metals’ mining and mineral processes have shown.
Life cycle assessments (LCA) on iron ore and bauxite mining and processing, by CSIRO ’s Minerals Down Under Flagship project engineers Terry Norgate and Dr Nawshad Haque, found that loading and hauling amounted to half of both processes’ total emissions.
The results were calculated using one tonne of ore or concentrate as a functional unit ready for transport to downstream metal extraction and refining facilities.
Mr Norgate says the work shows that efforts to reduce future greenhouse gas emissions over these stages of the life cycle - expected to increase as a result of falling ore grades and more finer-grained deposits - should concentrate on loading and hauling for these metals.
However, it is a different story for copper concentrates. An LCA found that reducing the ore’s size was the largest greenhouse gas contributor over the mining and mineral processing stages.
As copper ore has a lower grade compared to iron ore and bauxite, the crushing and grinding processes needed for processing it into concentrate contributes about 46 per cent of that ore’s greenhouse gas emissions.
Although copper ore processing produces the equivalent of 628 kilograms of carbon dioxide per tonne, compared to bauxite at 4.9 kg CO2 per tonne and iron ore at 11.9 kg CO2 per tonne, emissions from iron ore represents a greater issue for Australia, he says. “That’s because iron ore represents by far the largest amount of any metallic ore or concentrate exported from Australia. About 236 million tonnes are mined each year in Australia and most of that is exported," he says.
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