Microbes in an electrolysis cell (lower left) get a small boost from the power source. Hydrogen gas is released at the cathode and bubbles up and into the tube on top of the reactor.
Using ingredients that could be obtained from a salad bar, and adding some electricity producing microbes, researchers have developed a method that yields up to 91 percent hydrogen—the most efficient yet for the type of system they used.
In certain configurations of the device, nearly all of the hydrogen contained in the molecules of source material converted to useable hydrogen gas, an efficiency that could eventually open the door to bacterial hydrogen production on a larger scale.
"We achieved the highest hydrogen yields ever obtained with this approach from different sources of organic matter, such as yields of 91 percent using vinegar (acetic acid) and 68 percent using cellulose," said Bruce Logan, an environmental engineer at Pennsylvania State University who developed the reaction process with his coworker Shaoan Cheng.
Finding better methods for producing hydrogen is important because it’s an attractive alternative to gasoline for powering vehicles. It can be made from renewable resources—even waste—and it produces no greenhouse gases.
"Efficient and sustainable hydrogen production is possible from any type of biodegradable organic matter," they said in a recently published report.
The part of the device that doesn’t come from the salad bar, however, does come from the sewer. Logan had already established a method for coaxing electricity out of bacteria commonly found in wastewater. By adding a few modifications to improve conditions for the bacteria, and adding a small jolt of electricity, the researchers increased the hydrogen yield to a new record.
Other systems produce hydrogen on a larger scale, but few if any match the new system for energy efficiency.
Even with the small amount of electricity applied, the hydrogen ultimately provides more energy as a fuel than the electricity needed to drive the reactor. The overall efficiency of the vinegar-fueled system is better than 80 percent, far better than the efficiency for generation of the leading alternative fuel, ethanol.
Even most electrolysis techniques, methods to extract hydrogen from water using electricity, pale in comparison to the new method.
—Josh Chamot, NSF
The study was reported in the Nov. 12, 2007, online version of Proceedings of the National Academy of Sciences.
This report is provided by the National Science Foundation, an independent federal agency that supports fundamental research and education across all fields of science and engineering, in partnership with U.S. News and World Report.
