Hydrogen is a potentially valuable energy
source but production costs and environmental concerns about using fossil fuels
to produce the gas have limited its application so far. Previous studies have
shown hydrogen gas can be produced by harnessing the by-products of microbial
organic matter metabolism in a device called a microbial electrolysis cell. But
the process requires an additional input of electricity to make it work
effectively. Now, according to a study published in the Proceedings of the
National Academy of Sciences, hydrogen can be produced in a single device by
integrating a water-based power supply into the system.

ABC Science Online’s Rachel
Sullivan (20 September 2011):

Hydrogen – a potential clean
energy source – can be sustainably generated using just seawater, river water
and bacteria, according to new research.

Hydrogen is a potentially
valuable energy source but production costs and environmental concerns about
using fossil fuels to produce the gas have limited its application so far.

Previous studies have shown
hydrogen gas can be produced by harnessing the by-products of microbial organic
matter metabolism in a device called a microbial electrolysis cell.

But the process requires an
additional input of electricity to make it work effectively.

Now, according to a study
published online in the Proceedings of the National Academy of Sciences,
hydrogen can be produced in a single device by integrating a water-based power
supply into the system.

Exoelectrogenic bacteria are
found in ponds, streams, sediments and soils, as well as in waste water.

Because they metabolise organic
matter, they can transfer electrical energy to conductive materials such as
metal or graphite.

“[When they are used in
Microbial Electrolysis Cells] bacteria produce electrical current, but not
enough voltage to drive hydrogen gas production at the other electrode,”
Professor Bruce Logan from Pennsylvania State University’s Hydrogen Energy
(H2E) Centre said.

Salt gradient

Professor Logan and Dr Younggy
Kim designed a microbial reverse electrodialysis system, containing five pairs
of seawater and river water cells separated by thin membranes, which were
sandwiched between an anode containing the bacteria, and a cathode.

The passage of salt through the
membranes down the gradient of seawater to river water generated the additional
electricity needed to produce hydrogen without the need for fossil fuels,
sunlight, or wind.

“The most significant
finding is that hydrogen production is possible using readily available and
sustainable sources, and with no need for electricity [input],” Professor
Logan said.

Because the bacteria in the
device can be fed organic waste, the system may also prove useful for
wastewater treatment.

“The implication of this
research is that waste water can become a resource from which we can actually
capture energy in the very useful form of hydrogen gas” – without any
consumption of electrical grid energy,” he said.

Dr Rene Rozendal, a former
research fellow at the University of Queensland’s Advanced Water Management
Centre and the inventor of microbial electrolysis, says this is an interesting study

“However, due to the large
amount of membranes [and electrodes] required, it is a rather expensive method
of making hydrogen gas,” he said.

“Moreover, the number of
places where salt and fresh water and large amounts of biodegradable organic
matter occur together are rather limited.”

“Still, it is a nice
proof-of-principle that demonstrates that hydrogen can be produced from natural
resources without electricity input.”

Source: www.abc.net.au