Hydrogen as an everyday environmentally friendly fuel source may be closer than we think, according to US researchers.

"The energy focus is currently on ethanol as a fuel, but economical ethanol from cellulose is 10 years down the road," said Bruce E. Logan, Kappe Professor of Environmental Engineering at Penn State University.

"First you need to break cellulose down to sugars and then bacteria can convert them to ethanol."

Professor Logan and research associate Shaoan Cheng have suggested a method based on microbial fuel cells to convert cellulose and other biodegradable organic materials directly into hydrogen.

The researchers used naturally occurring bacteria in a microbial electrolysis cell with acetic acid, which is found in vinegar and is the predominant acid produced by fermentation of glucose or cellulose.

The bacteria consume the acetic acid and release electrons and protons creating up to 0.3 volts. When more than 0.2 volts are added from an outside source, hydrogen gas bubbles up from the liquid.

"This process produces 288 per cent more energy in hydrogen than the electrical energy that is added to the process," explained Professor Logan.

Water hydrolysis, a standard method for producing hydrogen, is only 50 to 70 per cent efficient.

Even if the microbial electrolysis cell process is set up to bleed off some of the hydrogen to produce the added energy boost needed to sustain hydrogen production, the process still creates 144 per cent more available energy than the electrical energy used to produce it.

Professor Logan suggested that hydrogen produced from cellulose and other renewable organic materials could be blended with natural gas for use in natural gas vehicles.

"We already drive a lot of vehicles on natural gas, which is essentially methane," said Professor Logan. "Methane burns fairly cleanly, but if we add hydrogen it burns even more cleanly and works fine in existing natural gas combustion vehicles."