State of the Environment Report 2007
Snapshot: Mugga Lane Power Generation Project – Canberra’s energetic underground
Canberra’s underground is an energetic scene. The wastes we send to our landfill sites are working away sight unseen with consequences, which may be good, or bad, depending on what we do. Organic material such as food scraps, paper and garden rubbish breaks down in a landfill, producing gases, mostly methane (up to 60%) and carbon dioxide. Both add to our greenhouse problems if they seep into the air. Methane is a particular greenhouse problem because it has 20 times the impact of carbon dioxide on the atmosphere. But methane is also very suitable as a fuel in gas engines. So, in Canberra’s tips, steps have been taken to capture and use the gas.
There are several projects, including a power plant installed at Mugga Lane tip in 2005 to generate continuously at approximately 3 megawatt (MW). Each MW generated uses around 650 cubic metres of landfill gas each hour. The electricity produced supplies the power needs of up to 1000 homes, reduces greenhouse gases from the landfill by up to 87% each year and, in sum, can reduces methane from the landfill by over 1,700 tonnes each year, which is like taking over 4,000 cars off the road.
The gas is extracted by drilling wells into the landfill. A vacuum is applied to the wells and the gas flows to the power station, where it is filtered and stripped of water. It then burns in an internal combustion engine which in turn drives a generator: electricity is produced which feeds to the local network – and is available as renewable energy.
The benefits to the community from capture and use of landfill gas are multiple: greenhouse emissions are cut, power is produced and the demand on fossil fuel sources is reduced. The capture also reduces health and safety issues such as odour emissions and the potential for landfill fires exacerbated by gases. Rehabilitation of the landfill once it closes is also improved as, were it to remain, gas moving up through the landfill would prevent oxygen from reaching plant roots.