In 2008, Yaniv Scherson, one of Cantwell's graduate students, was looking for a suitable topic for a doctoral thesis that would incorporate the thruster research.
"We wondered whether nitrous oxide could be exploited as an emissions-free source of energy," Cantwell said. "Since the product of the decomposition reaction is simply oxygen-enriched air, energy is generated with zero production of greenhouse gas. But first we needed to find a cheap, plentiful source of nitrous oxide."
Scherson eventually turned to Criddle, who had spent years studying microbial communities in wastewater treatment plants. Criddle explained that wastewater sludge contains bacteria that naturally convert nitrogen wastes into nitrous oxide, providing Scherson a cheap source of the gas.
Soon, Scherson, Criddle and Cantwell joined forces in a unique experiment bridging two very different fields space propulsion and environmental biotechnology. "It took a couple of rocket scientists to make this happen," Criddle said.
The result was a novel design with the potential for treating the world's wastewater: First, reduce oxygen levels at the treatment plant to encourage the production of nitrous oxide and methane gas. Then use the extra methane to power the plant and a small rocket thruster to break down the nitrous oxide into clean, hot air. "A single thruster about the size of a basketball could potentially consume every ounce of nitrous oxide produced by a typical treatment plant," Cantwell said.
Most treatment plants in the United States are using technology developed in the 1970s and are in dire need of an overhaul, according to Criddle. "In the U.S., we haven't invested much in wastewater treatment in recent decades," he said.
|Contact: Mark Shwartz|