Within the sludge of wastewater treatment plants is an invisible world teeming with microbes. Here, diverse species of bacteria convert solid and liquid wastes into gases, some of which contribute to global warming.
Now two Stanford University engineers are developing a new sewage treatment process that would actually increase the production of two greenhouse gases nitrous oxide (aka, "laughing gas") and methane and use the gases to power the treatment plant.
"Normally, we want to discourage these gases from forming," said Craig Criddle, a professor of civil and environmental engineering and senior fellow at the Woods Institute for the Environment at Stanford. "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."
Criddle, an expert in wastewater management, has joined forces with Brian Cantwell, a professor of aeronautics and astronautics, who has spent the last five years designing rocket thrusters that run on nitrous oxide.
With support from a Woods Institute Environmental Venture Projects grant, Cantwell and Criddle are applying that rocket technology to sewage treatment, with the goal of making the process energy neutral and emissions free.
"We want to reduce the cost of wastewater treatment, increase energy generation and eliminate greenhouse gas emissions," Cantwell said.
"For too long we've thought of treatment plants as places where we remove organic matter and waste nitrogen," Criddle added. "We need to view these wastes as resources, not simply something to dispose of."
For Criddle and Cantwell, the first step in building a green treatment plant is raising the right kind of bacteria. "We're really managing a zoo," Criddle said. "To get the right microbes, we need to encourage the growth of bacteria that produce nitrous oxide gas."
|Contact: Mark Shwartz|