• 04.03.12

Cleaning Our Waste By Turning It Into Electricity

What happens when you flush the toilet? The government has to spend a lot of money cleaning up your mess. What if the processes of cleaning that water also created electricity? That’s what they call synergy.

A washing-machine-sized device that runs on bacteria in wastewater could make an impact on developing countries. The device makes electricity from wastewater and then cleans up the sewage. That could lead to free wastewater treatment, and a giant boon for the developing world and areas short on water.


While wastewater treatment is ubiquitous in the developed world, it is still a costly struggle for many areas of the globe. Current wastewater technology involves a number of steps to separate and reduce sludge, all of which takes power–some estimates put the power use at 2% of overall consumption in the U.S.

The scientists, who presented their work at this year’s American Chemical Society meeting in San Diego are focusing on being able to vastly scale up the microbial fuel cell they have created, said Orianna Bretschger, from the J. Craig Venter Institute. “Over the last year, we have scaled systems out of lab into 100 gallon system, and improved efficiencies from 2% to 13%,” she says, adding that they are working on making systems more functional and improving electrical output.

Traditional fuel cells convert fuel directly into electricity without igniting the fuel. They react or combine hydrogen and oxygen, for instance, and produce electricity and drinking water. Microbial fuel cells, like those described by Bretschger, use organic matter, such as the material in sewage, as fuel, and microbes break down the organic matter. In the process, the bugs produce electrons. Added bonus: The microbes may even be able to break down harmful pollutants in the sludge.

Bretschger says that the lab is already working with water treatment facilities in San Diego, and hopes to commercialize the product by 2015. “This is where we started: The initial reactor cost $450,000 per cubic meter to clean the water,” she says. The current system costs less than a tenth of that, which works out to $150 per gallon. The group hopes eventually to bring the cost under $20 per gallon or less to be cost competitive with existing water treatment technologies.

“The potential energy contained in the waste we throw away is tremendous,” says Bretschger. In San Diego alone, she says, 800 million gallons of sludge are generated annually–enough to power 125 homes for an entire year. The new system wants to harness about 10% of that energy. That may not sound like much, says Bretschger, but with those 10% savings, wastewater treatment could be done for free.