From waste to electricity

tipping 400px

Filling an old open cut mine with Sydney’s garbage is actually better for the environment than dumping it at the tip. Julian Edgar explains why.

When it comes to municipal waste, there are no easy answers. Even with householders diligently sorting their garbage for recyclables and green waste, cities still produce enormous amounts of rubbish that require disposal. The traditional approach has been landfills, where the waste is piled and compacted, over time forming unsightly mountains of dirt-covered garbage. And it’s not just the visual blight that’s associated with traditional landfills: there’s also atmospheric methane emissions and potential toxic leachate to ground and surface waters.

But there is another way.

Woodlawn Bioreactor

It’s not perfect but it’s an option that is better for the environment and can also be used to produce electricity. It’s called a bioreactor and is more than just theory: a bioreactor is currently being used to dispose of 400,000 tonnes per year of Sydney’s garbage.

Located near Goulburn in New South Wales, the Woodlawn Bioreactor is run by Veolia Environmental Services. Based on a disused open cut mine, the 6000 hectare site is currently being used to dispose of municipal waste and generate electricity. Aquaculture and horticulture facilities are in trial phases.

The site was originally a copper, lead and zinc mine with major open-cut and underground mine workings. The mine closed in 1998 and Veolia took over the lease for the site in 2004. In addition to the workings, the site is extensively degraded with large tailings dams and unvegetated areas that once housed crushers and other industrial facilities. The underground shafts are abandoned but the huge 25 million cubic metre open-cut pit is being used as the new rubbish repository.

But how does the garbage get to the Woodlawn site, 250 kilometres from Sydney? The major transport component is by train. The garbage is compacted into purpose-built shipping containers at Clyde Transfer Terminal in Sydney. Each container takes the equivalent of three garbage trucks of material. The containers are then placed on railway wagons—no less than 56 of them carrying 1500 tonnes of waste per train.

The train, hauled by three diesel locomotives, leaves Sydney early each week-day morning, arriving at the Crisps Creek Intermodal Transfer Station, near the hamlet of Tarago, at 6am. At the transfer station, built specifically for the bioreactor, large forklifts place the containers on trucks that transport the garbage to the bioreactor, about 10 kilometres away.

Read the full article in ReNew 114

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