Energy consumption and
greenhouse gas emissions
OZ Minerals continues to work towards increased energy efficiency; in 2011, we publicly reported our greenhouse gas and energy emissions for the financial year 2010–2011 through the National Greenhouse and Energy Report System (NGERS). There are two main areas of energy consumption for OZ Minerals; our plant, which utilises electricity from the main grid, and the diesel that we use to operate mining vehicles.
Total direct and indirect energy consumption January–December 2011 (GJ)
|Prominent Hill||Exploration3||Group Office||Total4|
1 Direct energy consumption (scope 1 emissions) – resulting from the on-site consumption of fuels and explosives or where electricity is generated.
2 Indirect energy consumption (scope 2 emissions) – due to the import of electricity from external parties; commonly the electricity grid.
3 Exploration data incorporates Carrapateena, Cobar and Cambodia.
4 Results reported in Gigajoules.
In 2011, we generated 331,983 tonnes of carbon dioxide equivalent emissions, of which 331,561 tonnes were emitted from our Australian sources predominantly Prominent Hill. While the majority of our energy is sourced from diesel, most greenhouse gas emissions are derived from electricity use. This is due to the higher emissions intensity of electricity compared with diesel.
Total direct and indirect greenhouse gas emissions January–December 2011
|Greenhouse gas emissions
|Prominent Hill||Exploration||Group Office||Total|
|Direct1 GHG Emissions||145,772||650||0||146,422|
|Indirect2 GHG Emissions||185,344||61||156||185,561|
1 Direct greenhouse gas emissions – resulting from the on-site consumption of fuels and explosives or where electricity is generated.
2 Indirect greenhouse gas emissions – due to the import of electricity from external parties; commonly the electricity grid.
We actively monitor and analyse our energy consumption and greenhouse gas emissions. We have our emissions independently verified and we publicly report our greenhouse gas emissions through our annual sustainability report and as part of the NGERS scheme.
As participants in the Carbon Disclosure Project and the Australian Government Energy Efficiency Opportunities (EEO) program we are undertaking a number of projects to increase our energy efficiency. One example is the installation of variable speed drives to enhance water and energy savings. The variable speed drives enable us to control the speed of the drive, so that when it is not needed, the speed of the pump can be turned down, reducing our energy and water use. This project has an energy saving of 3,920 gigajoules per annum. We have saved an additional 3,332 gigajoules per annum through in-pit excavator maintenance.
As a relatively new operation, we have a modern efficient plant, but are continuously and proactively looking for ways to increase our energy efficiency. In 2011, we completed our first Energy Efficiency Assessment. This assessment will be used as a baseline for comparison for future assessments.
We have a sound understanding of our greenhouse gas inventory, and disclose and audit it regularly. This detailed knowledge of our inventory enables us to make projections and influences our Prominent Hill mine plan. We monitor our energy usage against the mine plan. With this clear understanding of our operation, we have not set energy reduction targets for 2012. As our activity will increase, we expect a corresponding increase in energy usage.
In 2012, we will continue developing projects to increase our energy efficiency in line with our energy and greenhouse gas management plan. The development of a supply and demand model based on our input and output will ensure that we are able to track our energy efficiency. For more information on this model, please see the ‘Water and Diesel Supply Model’ case study.