Sewage more than just waste

Melbourne’s biggest sewage treatment plant, the Western Treatment Plant, has, for the first time, used sewage to produce more than enough biogas to power the entire plant for the last two months.

The Western Treatment Plant in Werribee (outer West Melbourne) treats about 60% of Melbourne’s sewage and has been leading the way in renewable energy since 2005. Electricity is generated from biogases captured in covered treatment lagoons. Biogas, mainly methane, is a by-product of sewage treatment.

Lagoon covers catch methane.

Melbourne Water General Manager of Asset Planning Paul Pretto said that the latest achievement at the Western Treatment Plant signals a big step forward for the organisation in how it produces and uses biogas.

“We’ve been producing about 95% of our power needs for a little while and are on track to do this for the year, but to have produced in excess of what we need to operate for two months in a row is better than we aimed for. It’s tremendous,” he said.

“The community has traditionally viewed sewage as a waste product, but that view is changing with improvements in technology meaning it can now be used to create energy.”

“We expect to increase the production of renewable energy by replacing and extending the covers that go over the lagoons and trap the methane gas.”

Methane covers.

The new covers are part of a $43 million project focusing on increasing biogas production which also included two new power generators to increase renewable-energy generation from 52 gigawatt hours per year to almost 72 GWh/yr.

“This will reduce greenhouse gas emissions by a further 24,400 tonnes of carbon dioxide per year, which is the equivalent to taking about 5600 cars off the road,” Dr Pretto said.

Since 2005, 270,000 megawatt hours of renewable electricity have been generated at the Western Treatment Plant, preventing the emission of about 330,000 tonnes of greenhouse gases.

Melbourne Water has beaten its own goal of making the plant energy self-sufficient for two months but hopes to produce at least 100% of its needs consistently by 2013.

“We can now look into what other aspects of our business we can supply biogas for in the future, reducing our carbon footprint across our many sites,” added Dr Pretto.

As part of this commitment, Melbourne Water has signed a 20-year contract with energy company AGL. AGL currently owns and operates the biogas-fired power plant at the Western Treatment Plant and supplies the corporation with renewable electricity at sites that can’t produce enough of their own renewable energy.

A focus on producing renewable energy can also be seen at the Eastern Treatment Plant in Bangholme.

“We have upgraded the power station and outfall pumping station at our Eastern Treatment Plant to improve biogas utilisation to generate electricity for the plant in the same way it is at the Western Treatment Plant.

“At the Eastern Treatment Plant better utilisation of the renewable energy source will further reduce greenhouse gas emissions by replacing imported electricity and by almost eliminating the use of diesel fuel at the plant,” said Dr Pretto.

Methane gas burn-off.

“Across Melbourne Water we’re aiming to meet all of our energy needs from renewable sources and have zero net greenhouse gas emissions by 2018.”