Melbourne Water - Werribee, Biogas Facility

Grid connected, renewable distributed generation
Location: Werribee, VIC

Wastewater biogas

Sewage wastewater can either be processed aerobically (in the presence of oxygen) or anaerobically (oxygen excluded). The anaerobic process produces methane,which in this project is collected and used to generate renewable power. If not collected and used for power production the methane would either be flared or vented to atmosphere with adverse environmental impacts.

Werribee Sewage Plant

The Werribee Sewage Plant is being transformed from an open lagoon treatment plant to an anaerobic plant. Portions of the lagoon receiving raw sewage wastewater are covered, oxygen is excluded, an anaerobic reaction is produced and methane is generated. In 1995 two 0.63 MW engines were installed. AGL has now installed two additional 1.25 MW reciprocating engine generating sets. Sections of the lagoons remain uncovered and pumps agitate these sections to introduce oxygen, further processing the wastewater, which is eventually discharged into Port Phillip Bay.

Power generation and sales

There are two power supplies to the site,and each generator is connected to an incoming supply. Power is generated at 415 volt and stepped up to 22,000 volts for connection to the Powercor distribution network. The power plant operates in base load mode and all power is sold to Melbourne Water.

Gas reticulation

The site is large, and extensive reticulation was required to deliver gas to the generating plant. Blowers are used to deliver the biogas at a low positive pressure. AGL has been responsible for the total site development and control of gas delivery to the plant.

Site

The power generators are containerised and the gas processing plant including scrubbers and gas conditioning are contained in a central compound.

Environmental impact

The Werribee project will significantly reduce the greenhouse gas emissions associated with power generation. At full capacity,Werribee will produce around 25,000 MWh of green electricity per annum, which will reduce greenhouse gas emissions by 20,000 tonnes per annum. In addition the capture of methane significantly reduces odours from the site familiar to Melbourne-to-Geelong travellers.