The Western Treatment Plant in Werribee, Victoria, largely powers itself using biogas – a by-product of sewage treatment. Jason Patrick Ross/Shutterstock
Could what we flush down the toilet be used to power our homes? Thanks to biogas technology, Australia’s relationship with organic waste – human and animal excreta, plant scraps and food-processing waste – is changing, turning waste into a commercial source of renewable energy.
A recent report suggests that Australia produces about 20 million tonnes of organic waste per year from domestic and industrial sources. This in turn accounts for a large portion of national greenhouse gas emissions. Manure from livestock industries alone accounts for 22 Mt of carbon dioxide equivalents.
Organic waste, when broken down by bacteria, produces a methane-rich “biogas” that can be used to generate electricity and heat.
According to one estimate, if all the organic waste from Australian domestic, industrial and agricultural industries was treated in biogas plants, it would have the potential to produce around 650 megawatts of electricity. That’s enough to power almost one million Australian homes.
How it works
Getting the process right can be tricky but the science is simple: fill an airtight tank known as an anaerobic (oxygen-free) digester with slurry made from biological waste, then let the bacteria get to work to produce a methane-rich gas that can be used to generate electricity and heat.
Use what you need to power your pumps, motors and circuitry, and sell the rest back to the grid so that in as little as five years you recoup what you’ve outlaid on your biogas plant.
Renewable energy provided 14.8% of Australian electricity generation during 2013. Bioenergy totalled 7% of this, with biogas contributing to about 2.0% of the share of total renewable electricity capacity. In comparison, wind stands at 26% while solar power is 11%. The bioenergy industry expects biogas could be more important than solar, and as important as wind. The remainder of Australian bioenergy comes mostly from the combustion of sugarcane waste, also known as bagasse.