Fuel of the Future (Long)
Posted: Mon Feb 21, 2000 7:06 pm
By BBC News Online's Damian
Carrington in Washington DC
Petrol stations could be replaced by
stagnant ponds if a breakthrough in
hydrogen fuel technology fulfils its
potential.
The new approach
harnesses an emergency
survival strategy that
green algae use to survive
during hard times. The
microscopic plants switch from normal
photosynthesis, producing carbon dioxide,
to an alternative way of "breathing" which
produces hydrogen gas.
The theoretical yields are high enough for
the process to be exciting experts in the
energy field as a future source of fuel,
perhaps in 20 years time.
The fuel could be used to power fuel cells
in cars. The big advantage of hydrogen as
a fuel is that it does not produce carbon
dioxide or other pollutants when it is burnt
in pure oxygen. And if produced by using
solar energy to split water, it is entirely
sustainable.
The new research was led by Tasios Melis,
from the University of California-Berkeley.
"I guess it's the equivalent of striking oil,"
he told the annual meeting of the
American Association for the
Advancement of Science (AAAS).
He estimates that a small pond in which
the growth of the algae is controlled could
provide enough fuel for 12 cars for a
week.
Airtight pond
The key to the process is the element
sulphur. The algae need this nutrient to
grow and when it is not available, the
algae begin to consume the oxygen in the
water. In a short time, the system
becomes stagnant and, said Professor
Melis, "every other plant on Earth would
suffocate and die".
"This algae do not - they have a trick."
They switch to a different metabolic
pathway which produces hydrogen.
So to use the algae
is a two step
process. First they
are grown, then the
sulphur is removed
and a day later the
hydrogen starts to
flow. This continues
for a few days
before the algae are
so starved they
must be returned to
normal photosynthesis.
However, there appears to be no limit to
the number of times this cycle can be
repeated, according to Professor Melis.
This approach could be applied to a pond
by using an airtight cover.
Currently, the process produces three
millilitres of hydrogen per litre of algae
solution, but improvements to the system
should deliver 10 times this amount. The
conversion efficiency of the sunlight
energy would be about 10%.
Maggie Mann, from the National
Renewable Energy Laboratory, Colorado,
said biophotosynthesis was likely to be
one important way of producing hydrogen
fuel in the future.
Fuel from sewage
It also has advantages over using solar
energy to electrically produce hydrogen as
there is no need to manufacture solar
panels.
Future work in the area involves
developing mutants of the algae which
can tolerate oxygen whilst still producing
hydrogen - oxygen destroys the key
enzyme in the process, called
hydrogenase.
Elias Greenbaum, from Oak Ridge National
Laboratory, is using laboratory techniques
to select out algae that have a natural
tolerance for oxygen.
"We do this by telling them that they have
to produce hydrogen or they die," he said.
If oxygen-tolerance could be achieved,
then the two-stage production cycle could
be simplified to one, continuous process.
It may even be possible to convert
sewage into hydrogen fuel. Tadashi
Matsunaga, at the Tokyo University of
Agriculture and Technology, has found a
photosynthesising bacterium which
produces hydrogen from waste water.
Carrington in Washington DC
Petrol stations could be replaced by
stagnant ponds if a breakthrough in
hydrogen fuel technology fulfils its
potential.
The new approach
harnesses an emergency
survival strategy that
green algae use to survive
during hard times. The
microscopic plants switch from normal
photosynthesis, producing carbon dioxide,
to an alternative way of "breathing" which
produces hydrogen gas.
The theoretical yields are high enough for
the process to be exciting experts in the
energy field as a future source of fuel,
perhaps in 20 years time.
The fuel could be used to power fuel cells
in cars. The big advantage of hydrogen as
a fuel is that it does not produce carbon
dioxide or other pollutants when it is burnt
in pure oxygen. And if produced by using
solar energy to split water, it is entirely
sustainable.
The new research was led by Tasios Melis,
from the University of California-Berkeley.
"I guess it's the equivalent of striking oil,"
he told the annual meeting of the
American Association for the
Advancement of Science (AAAS).
He estimates that a small pond in which
the growth of the algae is controlled could
provide enough fuel for 12 cars for a
week.
Airtight pond
The key to the process is the element
sulphur. The algae need this nutrient to
grow and when it is not available, the
algae begin to consume the oxygen in the
water. In a short time, the system
becomes stagnant and, said Professor
Melis, "every other plant on Earth would
suffocate and die".
"This algae do not - they have a trick."
They switch to a different metabolic
pathway which produces hydrogen.
So to use the algae
is a two step
process. First they
are grown, then the
sulphur is removed
and a day later the
hydrogen starts to
flow. This continues
for a few days
before the algae are
so starved they
must be returned to
normal photosynthesis.
However, there appears to be no limit to
the number of times this cycle can be
repeated, according to Professor Melis.
This approach could be applied to a pond
by using an airtight cover.
Currently, the process produces three
millilitres of hydrogen per litre of algae
solution, but improvements to the system
should deliver 10 times this amount. The
conversion efficiency of the sunlight
energy would be about 10%.
Maggie Mann, from the National
Renewable Energy Laboratory, Colorado,
said biophotosynthesis was likely to be
one important way of producing hydrogen
fuel in the future.
Fuel from sewage
It also has advantages over using solar
energy to electrically produce hydrogen as
there is no need to manufacture solar
panels.
Future work in the area involves
developing mutants of the algae which
can tolerate oxygen whilst still producing
hydrogen - oxygen destroys the key
enzyme in the process, called
hydrogenase.
Elias Greenbaum, from Oak Ridge National
Laboratory, is using laboratory techniques
to select out algae that have a natural
tolerance for oxygen.
"We do this by telling them that they have
to produce hydrogen or they die," he said.
If oxygen-tolerance could be achieved,
then the two-stage production cycle could
be simplified to one, continuous process.
It may even be possible to convert
sewage into hydrogen fuel. Tadashi
Matsunaga, at the Tokyo University of
Agriculture and Technology, has found a
photosynthesising bacterium which
produces hydrogen from waste water.
)