Moranbah North Power Station generates electricity from methane-rich gas that is released during underground mining operationsSummary
Anglo American recognises the challenge posed by climate change and our responsibility to take action to address its causes and to protect our employees and assets, as well as our communities, against its potential impacts. We have set an interim goal of achieving the maximum economically sustainable energy and Green House Gas (GHG) savings in our business and in the use of our products. Technology plays a key role in delivery of our climate change strategy.
Our coal mining operations in Australia and South Africa have been investing in very different technologies, both of which can significantly reduce our methane emissions.
Background
Methane is found, in differing concentrations, in the majority of coal seams where it was produced during the formation of the coal from peat. It is released when the coal bed is broken up during the mining process or through natural geological events such as erosion.
Within a mine, methane is a significant health and safety risk. While it is not toxic, it is an asphyxiant, is highly flammable, and potentially explosive. A concentration of methane therefore needs to be managed.
Most coal companies will drain as much methane gas from coal seams before mining commences to prevent the risk of outbursts and control gas concentrations as mining progresses. In underground mines, once mining commences the workspace is continually ventilated to dilute any methane present to safe levels. This is often referred to as ventilation air methane or VAM and is typically vented to the atmosphere.
However, methane is also a greenhouse gas (GHG) that is 21 times more damaging to the environment than CO2, and thus venting is an increasingly unacceptable option – and in some countries is illegal. It accounts for 17% of Anglo American’s carbon footprint and is our largest single source of GHG emissions.
What you do with it, to some extent, depends on how much of it there is and how concentrated.
In our underground metallurgical coal mines in Australia, methane is highly concentrated, which makes large-scale, capture-and-use initiatives for this ‘rich’ gas viable. Examples are the Moranbah North and Capcoal power stations.
Our coal business in Australia has invested more than A$120 million over the past five years to abate eight million tonnes of CO2 equivalent emissions using all available commercial scale technologies. As a result this business aims to eliminate rich gas emissions from venting by 2013.
Technologies for utilizing rich methane gas for power generation are well established. But tackling the emission of more dilute ventilation air methane (VAM) which is suctioned-out from underground workings is more complicated. Technologies for treating fugitive emissions, particularly VAM are at the early stages of the innovation chain and require significant investment in terms of time and research to demonstrate and deploy on a wide-scale.
Technical and safety issues associated with the capture and handling of these fugitive emissions suggests that there is a technology gap of around 10 years before a solution is likely. Nonetheless, Anglo American is partnering with the chemical company Johnson Matthey on a pilot project using catalysts for the capture and use of VAM.
And meantime in South Africa, our New Denmark colliery has developed an innovative mobile flaring system to reduce its methane emissions from ventilation boreholes.
Moranbah North
Moranbah North is a metallurgical coal mine in central Queensland, Australia.
From late 2008, our metallurgical coal business has supplied two dedicated gas fired power stations with coal seam methane piped from Moranbah North and the nearby Capcoal mine. Though highly damaging when released as a gas, when it is burnt methane is one of the cleanest fossil fuels. It produces less carbon dioxide for each unit of heat produced than other hydrocarbon fuels.
The Moranbah North power station produces [45] MW of electricity for the Australian national grid. By capturing methane, which would otherwise have been vented, these power stations prevent 2.5 million tonnes of CO2 equivalent emissions from entering the atmosphere each year – and generate 75MW of electricity.
This electricity is enough to power 48,000 homes, and the emission savings are equivalent to taking 500,000 cars off the road – or planting 3.6 million trees.
New Denmark
An innovative methane flaring project at the New Denmark colliery in north eastern South Africa, is expected to reduce the mine’s annual methane emissions by 15% – and will more than pay for itself within three years.
Flaring burns off methane, rendering it 18.5 times less harmful to the environment than venting.
The project was initiated by Johan Janse van Rensburg, a ventilation and occupational hygiene engineering specialist at the mine. He helped to design what is the world’s first mobile flaring-off mechanism; and two of the flares have been incorporated into the mine’s methane drainage system at a project cost of R9 million (US$1.3 m).
Working with external partners, Johan also discovered that under the Kyoto Protocol, methane flaring is an eligible Clean Development Mechanism (CDM) activity. As a result, the project could generate more than $8 million in revenue in its first decade through the sale of Certified Emission Reduction credits – making it financially viable.
This project has turned an environmental liability into an asset.