From garbage to energy at the Woodlawn Bioreactor, NSW.

This old mine pit is used to collect methane gas from garbage to run electricity generators (photo Julie May)

The Woodlawn zinc and copper mine was shut in 1998 (although the mine has reopened this year). The original mine left a large pit which Veolia (Australia and New Zealand) uses to store garbage from Sydney. The garbage is covered with soil and methane gas made from the bacterial decomposition of plant and animal matter is collected, then used to run 7 landfill gas engines (92% of the methane is captured). This bioreactor started operation in 2004.

For every tonne of waste deposited at the facility, 1.33 megawatts of clean electricity can be produced. Since opening, over 4.1 Mt of waste has been processed most of which has been used to generate green electricity.

Although burning methane has carbon dioxide as a waste product, it is 21% more potent than CO2 as a greenhouse gas, so overall greenhouse gas effects are reduced. In addition, electricity is made from waste, a renewable resource, and production is 24/7 so it is base load power.

The landfill gas engines (photo Julie May)

Other sustainable and energy saving mechanisms and products are employed:

• The garbage is compressed into containers at two highly efficient rail transfer terminals in southern Sydney. Trains, on the original Sydney-Canberra line, carry the containers to Tarago where they are put on trucks for the short journey to Woodlawn.
• Waste heat from one gas turbine is used to warm the water of a barramundi fish farm. (Some of the fish are sold at the Belconnen Markets in nearby Canberra.)
• There is a new, separate 'waste to compost' facility, which separates out the organics from household waste to create compost and soil. The soil will be used to help rehabilitate mine tailings to grassland.
• The land supports a sheep farm which uses rotational grazing.
• The land also has 23 wind turbines owned by Infogen, producing 48MW.
• Soon the facility will have its own 2.5MW solar farm.

For more information see: Veolia's Woodlawn Bioreactor, NSW