Yahoo News 13 Nov 07;
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.
Biological Reactors Make Hydrogen Fuel from Sewage
Charles Q. Choi, LiveScience.com, Yahoo News 13 Nov 07;
All kinds of biodegradable garbage—from sewage to leftover food—could yield valuable hydrogen fuel, an alternative to fossil fuels, with the aid of microbes cultivated in special reactors.
When hydrogen is burned, it yields just energy and water. That being an attractive sort of fuel, researchers globally are investigating ways to generate hydrogen en masse in hopes of replacing fossil fuels, the burning of which releases the global warming gas carbon dioxide. Unfortunately, most of the hydrogen available today for use is actually generated from fossil fuels.
Now environmental engineers at Pennsylvania State University are perfecting a way of generating hydrogen from biodegradable garbage—that is, organic matter from plants, animals and other organisms. The idea, first announced in 2005 but improved upon in newer work, is to take liquid waste, such as effluent from sewers, breweries or food processing plants, and feed it to soil- or wastewater-derived bacteria raised in reactors designed to foster their growth. These microbes then break down the organic matter, releasing hydrogen gas.
"We could use all sorts of wastewaters, turning them into hydrogen instead of using energy to treat the wastewater," Penn State researcher Bruce Logan told LiveScience.
These microbes do need a low voltage supplied by researchers to generate the hydrogen, which Logan and colleagues discovered in 2005. Still, burning some of the hydrogen the bacteria produce can help generate the electricity the germs require to make the gas. Back in 2005, the researchers envisioned the process largely as a way to cut down on the cost of dealing with sewage. Now, they say the reactors can prove significantly efficient as hydrogen producers.
For example, when given acetic acid—a common leftover of fermentation—the bacteria in the reactors generated hydrogen at up to nearly 99 percent of the theoretical maximum yield. The reactors also worked when stuffed with cellulose, found in plants.
"This could really make a hydrogen economy work from renewable energy sources," Logan said.
Future research will focus on improving the rates of hydrogen production and lowering the cost of reactor materials.
"We hope to see pilot tests of this soon," Logan said. "We have been contacted by several companies, but so far no plans—yet—for a demonstration project."
Logan and his colleague Shaoan Cheng detailed their findings online Nov. 12 in the Proceedings of the National Academy of Sciences.
