U.S. researchers say they have shown how cells feed on bacteria can be "powered" and produce an unlimited amount of hydrogen.
Until now, they explained, from a source external power was needed in the process.
However, the team added that the running costs of the new technology is too high it can be used for commercial purposes.
Information on the results was published in the Proceedings of the National Academy of Sciences.
"There are bacteria that occur naturally in the environment that are capable of releasing electrons outside the cell, so that it can actually generate electricity, since they are decomposing organic matter," said Bruce Logan co, author of the Pennsylvania State University, USA.
"We are using microbes, especially in a thing called a microbial fuel cell (MFC), to produce electricity.
"We can also use them for this device, where they need a little 'more power to make hydrogen gas.
"What this means is that they produce electricity, which are electrons, they release protons in water, and these values are combined with electrons."
Prof Logan said that the technology uses this process to produce hydrogen, called the microbial electrolysis cell (MEC).
"The breakthrough here is that it is necessary to use an energy source to power a little longer in the system.
Performance of hydrogen molecules (Image: Science Photo Library) hydrogen has long been hailed a transportation fuel in the future, but has yet to realize its potential
"Everything we do is add a little fresh water and a little salt and some membranes, and the electrical potential that is there can not give that power."
MEC to use something called "reverse electrodialysis" (RED), which applies to energy collection from the difference between the salinity or salt content between fresh and salt water.
In their paper, said Professor Logan and colleague Kim Younggy imagined how a system would be the use of red cell membranes of rotation of harvesting this energy, the movement of charged atoms move from salt water in fresh water creates a small voltage that can be put to work.
"This is the crucial element in the latest research," Prof. Logan told BBC News that explain the process of their system, known as an electrolytic cell microbial reverse electrodialysis (MREC).
"If you think of desalinated water, energy is needed. If you have an interface saltwater and freshwater, which can add energy. We realized that only a little of this energy could make this process go on their own. "
The beginnings
He said the technology was still in its infancy, it was one of the reasons why it has not been commercially exploited.
"Right now is a new technology," he said.
"In a sense it is as solar energy. We know we can convert solar energy into electricity, but it took many years to reduce the cost.
"It's a similar thing: it is a new technology, and it could be used, but right now, it's probably a bit expensive, so the question is, can we reduce costs.?"
The next step, Professor Logan said, was to develop larger cells, "Then it becomes easier to assess the costs and investments needed to use the technology.
The authors acknowledged that hydrogen had "great potential as an energy efficient", but carried out with high production costs and environmental concerns, as is most often produced using fossil fuels.
Professor Logan said: "We use hydrogen, for many, many things are used in the manufacture of [gasoline], which is used in food, etc. What you use in transport remains to be seen ... .."
But the authors wrote that their findings offered hope for the future. "This is a unique type of integrated system is well positioned to manage wastewater, and at the same time produces a [hydrogen] gas into electricity without the energy consumption "
Professor Logan said the work is an example of a microbial fuel cell is currently on display at London Science Museum as part of an exhibition of water wars.
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