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12. Greenhouse gas intensity reduction strategy is producing results
In 2002, BHP Billiton committed to reducing greenhouse gas (GHG) intensity (per unit of production) from operations by not less than 5 per cent between 2002 and 2007. A major contributor to the improvement has been our Aluminium CSG and, in particular, the aluminium smelters Hillside and Bayside in South Africa and Mozal in Mozambique.
Over the past year, members of the BHP Billiton Aluminium team took part in an initiative, led by the International Aluminium Institute (IAI), to develop protocols for measurement and management of GHGs in the aluminium industry. The IAI developed voluntary targets for the industry to apply to improvement efforts in GHG and other critical HSE performance areas. Our Aluminium CSG has fully supported the intent, workload and outcomes of the IAI initiative.
GHGs emitted from aluminium smelters are derived from various sources, including fuels used in parts of the smelting process and carbon anodes employed in smelting cells. GHGs in the form of perfluorocarbons (PFCs) are also emitted from smelting cells during process disturbances called anode effects (AE), which are measured in terms of frequency (AE per cell per day) and AE duration measured in minutes. In addition to the direct sources of GHG from the smelting process, emissions from the power industry are an indirect effect but can also be reduced, from the consumer perspective, by improving the power efficiency of the smelting process.
BHP Billiton Aluminium has focused on the reduction of GHG intensity across all the areas of operations and from all sources. As shown by the accompanying graph, emissions of PFCs at Bayside smelter are a major challenge in reducing GHG intensity; and therefore Bayside has been a principal focus.
Improvements to existing technologies have included reduction of process instability through improved process control systems and work practices. At Bayside smelter, for example, improvements to these systems on the Søderberg cells in B and C lines have had a significant effect. As a result of the work completed to date, AE frequency has reduced from 2.6 to below 1.5 per cell per day, and AE duration has been improved by more than 15 per cent. A contributor to the improvements has been the fleet of new anode-effect quenching vehicles, which enable more rapid action to prevent or manage AEs as they occur.
At Hillside smelter, the introduction of slotted anode technology and improvements to the fuel efficiency in the baking furnaces through improved sealing have provided the basis for significant improvement by reducing fuel consumption and improving power efficiency. At Mozal smelter, slotted anodes and fuel burner optimisation in the anode-baking furnace have provided improvements. For the future, fuel substitution is a key strategy.
The Aluminium CSG sees improvement in GHG emissions as being part of a long-term plan, where emissions improvement and business improvement go hand in hand. In the implementation of new production capacity, GHG intensity is an important process criteria.
The reduction lines at Hillside and Mozal and new capacity being brought online, all benefit from world's best practice technologies.
Implementation of technology and management of ongoing operation practices provide the basis for improving performance. The training and development of personnel to operate these technologies to their capability have proved effective, achieving the outcomes to date.
Contribution from each smelter to GHG emissions (tonne C02 equivalent/tonne Al)
