Danish City to Power Water Treatment Plant Using Sewage

Every city produces sewage, but now, Aarhus, Denmark is hoping to prove that their waste doesn't have to be, well, wasted. As New Scientist reports, the Danish metropolis will become the first city to power its water system using energy harnessed from sewage and wastewater.

After undergoing a $3.2 million renovation, Aarhus’s Marselisborg Wastewater Treatment Plant is now capable of creating heat and electricity out of biogas. The waste is served up as a meal to bacteria kept in 100-degree "digesters," or large tanks. Byproduct gases like methane are then burned, generating more than 150 percent of the electricity required to power the plant. Any surplus electricity is either used to supply fresh water to the city of 200,000, or is sold back to the grid.

The concept of using human waste as an energy resource isn’t a new one: Last year a study from the United Nations University’s Institute for Water, Environment, and Health reported that biogas produced by all the world’s human poop could provide energy to up to 138 million homes. Aarhus is the first city to integrate this innovative idea into their water system, and now cities like Chicago, San Francisco, and Copenhagen are interested in following suit.

For Aarhus’s success to be recreated elsewhere, water plants need to be big enough to produce large amounts of biogas and the wastewater they use has to be the right makeup (too much water dilutes the energy content). Cities also need to have the funding to make the necessary infrastructure upgrades. Aarhus Water’s investment in their plant was pricey, but savings in maintenance and electricity sold to the grid are expected to make it up in five years.