The smelting of aluminium is a very energy intensive process – and over 80 per cent of smelting greenhouse gas emissions are indirect (electricity-related) emissions. The remaining emissions come from direct (on-site) emissions plus the emissions associated with the production of alumina.
The greenhouse gas intensity of Australian primary aluminium production, not including emissions from alumina refining which are considered separately, remained steady at 15.6 tonnes of CO2-e per tonne of aluminium in 2011.
In 2011 direct (process) emissions of greenhouse gas (PFCs, carbon inputs, fuels) were 1.87 tonnes of CO2-e per tonne of aluminium – 0.4 per cent lower than in 2010 and 63 per cent lower than in 1990. PFC emissions rose slightly to 0.14 tonnes of CO2-e per tonne of aluminium, a 96 per cent improvement over 1990 levels.
Total direct greenhouse gas emissions from Australian aluminium smelters were reported as 3.67 million tonnes CO2-e in 2011, up 0.7 per cent compared to 2010 but still well down on the 1990 level of 6.26 million tonnes.
Emissions from the purchase of electricity fell 0.2 per cent on an intensity basis over 2010. Indirect emission levels are closely linked to production and are therefore sensitive to economic conditions.
Since 1990 aluminium production has increased by 58 per cent whilst total indirect emissions have risen by only 34 per cent. On an intensity basis, indirect emissions were down 15 per cent on 1990 levels.
Indirect emissions also arise from the consumption of alumina in the smelting process, with around two tonnes of alumina required to produce one tonne of aluminium. At current rates this is equivalent to around 1.4 tonnes CO2-e per tonne of aluminium produced. These emissions are included in our reporting of alumina emissions and not added to the aluminium results to avoid double counting.