The processes required to refine alumina from bauxite ore and to smelt aluminium from alumina require significant amounts of energy. If the energy is sourced from the consumption of fossil fuels such as fuel oil, coal and electricity generated from coal fired power stations, it follows that such production results in high emission levels.
Worldwide, governments are increasingly focussing on GHG emissions and the potential impacts on the environment and climate change. This has resulted in legislative changes including carbon taxes or introduction of emission trading schemes to accelerate innovation to reduce emission or stimulate increased reliance on cleaner or renewable energy sources. AWAC’s GHG emissions present sustainability and business challenges for the AWAC joint venture. Our focus and importantly, that of operating partner Alcoa is on decreasing GHG intensity by:
- increasing energy efficiency through process and technology improvements
- investigating alternative energy sources from low or no carbon based generation, (renewable options to meet large volume energy requirements are limited in many regions)
- advancing technological solutions for GHG abatement.
A major challenge is balancing the need to ensure energy security with energy diversification. Currently base-load electricity supply at AWAC’s Portland aluminium smelter in Victoria Australia depends on longer-term contracts, reducing opportunities to switch energy sources. Despite these hurdles, Alcoa continue to pursue opportunities to reduce the carbon intensity of the electricity AWAC purchases.
The Pinjarra alumina refinery in Western Australia has two onsite gas-fired cogeneration power plants. These co-generation plants operate on natural gas, a transitional fuel that is cleaner than the alternative coal generated power plants, operating at 75 per cent energy efficiency compared to 30 – 50 per cent for other power plants in Western Australia. Energy generated by these plants is estimated to save approximately 450,000 metric tonnes of greenhouse gas emissions annually compared to a similar-sized coal-fired plant. In addition, the cogeneration plants reduce the refinery emissions by 270,000 tonnes per year through more efficient steam generation. The research into whether using solar energy to power the calcination process is feasible has the potential to reduce non-renewable energy consumption at the refineries and therefore reduce GHG emissions.
Results and goals
In 2016 AWAC's total (on a full facility basis) absolute greenhouse gas emissions from AWAC’s declined by approximately 11.8% to 13.4 million tonnes from 15.2 million tonnes of CO2 registered in 2015. Approximately 47 per cent of the reduction in absolute GHG emissions compared to the 2015 result was due to the curtailment of the Point Comfort alumina refinery. 28 per cent related to the closure of the Suralco alumina refinery and the balance at the Portland aluminium smelter.
Performance on a CO2 intensity basis (metric tons of CO2e per tonne of production) demonstrates a substantial improvement from the base year of 2005 the past ten years with intensity dropping by 14.0 per cent for the smelting operations and 15.0 per cent for the global alumina refinery portfolio.
|Greenhouse gas emissions |
AWAC Full Facility of tonnes of CO2 equivalents.
|Direct (Scope 1)||10,510,513||10,535,150||10,330,772||8,986,055||7,788,387|
|Indirect (Scope 2)||9,995,224||9,645,096||8,123,143||6,180,774||5,588,770|
Scope 1 (direct GHG) emissions are those released directly by AWACs’ sites through direct use of energy sources on-site such as natural gas. Scope 2 or indirect emissions are those from power stations predominantly electricity that supply energy to AWAC’s sites and also associated with the generation of steam at the co-generation facilities located at the Pinjarra refinery.
Emissions Calculation Methodology
The Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (Revised Edition), Australia - National Greenhouse and Energy Reporting Act, Brazil GHG Protocol Programme and The Climate Registry: General Reporting Protocol. Emission per source calculated by applying WRI Calculation Tool