2007-11-13 10:18:13
Mon Nov 12, 4:51 PM ET
US researchers have developed a method of producing hydrogen gas from biodegradable organic material, potentially providing an abundant source of this clean-burning fuel, according to a study released Monday.
The technology offers a way to cheaply and efficiently generate hydrogen gas from readily available and renewable biomass such as cellulose or glucose, and could be used for powering vehicles, making fertilizer and treating drinking water.
Numerous public transportation systems are moving toward hydrogen-powered engines as an alternative to gasoline, but most hydrogen today is generated from nonrenewable fossil fuels such as natural gas.
The method used by engineers at Pennsylvania State University however combines electron-generating bacteria and a small electrical charge in a microbial fuel cell to produce hydrogen gas.
Microbial fuel cells work through the action of bacteria which can pass electrons to an anode. The electrons flow from the anode through a wire to the cathode producing an electric current. In the process, the bacteria consume organic matter in the biomass material.
An external jolt of electricity helps generate hydrogen gas at the cathode.
In the past, the process, which is known as electrohydrogenesis, has had poor efficiency rates and low hydrogen yields.
But the researchers at Pennsylvania State University were able to get around these problems by chemically modifying elements of the reactor.
In laboratory experiments, their reactor generated hydrogen gas at nearly 99 percent of the theoretical maximum yield using aetic acid, a common dead-end product of glucose fermentation.
"This process produces 288 percent more energy in hydrogen than the electrical energy that is added in the process," said Bruce Logan, a professor of environmental engineering at Penn State.
The technology is economically viable now, which gives hydrogen an edge over another alternative biofuel which is grabbing more headlines, Logan said.
"The energy focus is currently on ethanol as a fuel, but economical ethanol from cellulose is 10 years down the road," said Logan.
"First you need to break cellulose down to sugars and then bacteria can convert them to ethanol."
One of the immediate applications for this technology is to supply the hydrogen that is used in fuel cell cars to generate the electricity that drives the motor, but it could also can be used to convert wood chips into hydrogen to be used as fertilizer.
The study appears in the Proceedings of the National Academy of Sciences.