After wastes leave homes and businesses, they head over to treatment plants, where they are processed so that they don't contaminate the environment. This is a very complex process, given that the wastes themselves are a very complex type of matter. There are several stages to the decontamination procedure, several of which involve the use of microbes and bacteria, which break down fibers, producing gas and other byproducts. Two experts now believe they've found a way of using two of these gases to power up the treatment plants themselves.

Two of the most important byproducts of sewage treatment are the greenhouse gases (GHG) nitrous oxide – more commonly known as laughing gas – and methane. Both are important sources of alternative energy. Two Stanford University engineers now believe that they developed a system that could allow waste facilities to produce their own electricity, and maybe even spare some into the power grid. The secret to their approach is boosting the production of nitrous oxide and methane, capturing the GHG, and then using them to produce electrical current.

“Normally, we want to discourage these gases from forming. But by encouraging the formation of nitrous oxide, we can remove harmful nitrogen from the water and simultaneously increase methane production for use as fuel,” explains Stanford professor of civil and environmental engineering Craig Criddle. He is also a wastewater management expert, and a senior fellow at the Woods Institute for the Environment, which is also located at the university. In order to advance with his work, the scientist teamed up with aeronautics and astronautics professor Brian Cantwell, who is developing nitrous oxide-powered rocket engines.

“We want to reduce the cost of wastewater treatment, increase energy generation and eliminate greenhouse gas emissions,” Cantwell says. “For too long we've thought of treatment plants as places where we remove organic matter and waste nitrogen. We need to view these wastes as resources, not simply something to dispose of,” Criddle adds. The team is being funded with grant money secured from the Woods Institute Environmental Venture Projects. “We're really managing a zoo. To get the right microbes, we need to encourage the growth of bacteria that produce nitrous oxide gas,” Criddle concludes.