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Science

Algae as a fuel source

03:53 PM ET 02/21/00 Algae May Be Key to Hydrogen Fuel By PAUL RECER AP Science Writer    WASHINGTON (AP) _ Hydrogen may be an ideal fuel when the supply of oil and natural gas runs out, but the problem has been finding a way to produce it cheaply. Scientists now say the answer may be an ordinary pond scum.

   Green algae, a simple plant that grows all over the world, has
the unique ability to convert water and sunlight into hydrogen gas,
researchers said Monday at the national meeting of the American
Association for the Advancement of Science.

   Now scientists have found a new way to force the algae to make
hydrogen gas on demand, a process that could lead to an almost
limitless supply of fuel that burns without pollution and produces
only water as a waste product.

   Tasios Melis of the University of California, Berkeley, said
that the algae, one of the most ancient plants known, evolved the
ability to live in two radically different environments.

   When living in ordinary air and sunlight, it uses photosynthesis
like other plants. This process converts sunlight, water and carbon
dioxide into waste oxygen and the life-sustaining chemicals the
plant needs.

   But when the algae is deprived of a key nutrient, sulfur, and
forced to live in an anaerobic, or oxygen-free, environment, the
plant reverts to an alternate life style in order to survive. Under
these conditions, the algae makes hydrogen, said Melis.

   "It is sort of a metabolic switch,'' said Melis. "It is an
alternative way of breathing'' that the plant developed over
millions of years to survive where there is no oxygen or sulfur.
Those same conditions would kill other plants.

   In experiments, Melis said his laboratory first grows algae
cells in the ordinary way, giving the plant sunlight, nutrients and
water. The plant happily reproduces, growing millions upon millions
of new cells.

   Then, the researchers cut off the supply of sulfur and oxygen to
the algae, forcing it to click the metabolic switch to its
hydrogen-producing life style.

   "Within 20 hours, the algae turns on its switch, converting
from oxygen production to hydrogen production,'' said Melis. "We
have to seal the culture to prevent exposure to oxygen. Then we
collect the hydrogen as it bubbles out of the culture.''

   The gas comes out as pure, pollution-free hydrogen, he said.

   Melis said the hydrogen-making process has operated
experimentally for up to four days, the time it takes for the algae
to exhaust its internal resources. The researchers then converted
back to normal photosynthesis and the plant revives itself, ready
to start another cycle.

   "This has the promise of generating fuel from some of nature's
most plentiful resources _ sunlight and water,'' said Melis.

   One liter of algae culture, a little over a quarter of a gallon,
produces three milliliters of hydrogen, about a tenth of a fluid
ounce, per hour, said Melis. Researchers believe this efficiency
can be increased at least 100 fold, but that has yet to be
demonstrated.

   Algae growing in a small pond, he said, may eventually be enough
to power 10 cars, although Melis admitted, "I'm not saying how big
the pond would have to be.''

   The algae's alternate life style uses an enzyme, along with
sunlight, to extract hydrogen from water. The enzyme, hydrogenase,
is not found in higher plants. Some researchers are looking at ways
to transfer the gene for this enzyme into other plants and,
possibly, to force the enzyme to work in the presence of oxygen.

   Hydrogen has long been promoted as a fuel to replace fossil
energy sources. In the space program, hydrogen and oxygen are
combined to make a rocket propellant, such as in the main engines
of the space shuttle.

   Oxygen and hydrogen are an explosive mixture, but they can be
combined in a fuel cell to produce electricity and water. Fuel
cells electrify the space shuttle and were used successfully in the
Apollo program.

   Margaret K. Mann of the National Renewable Energy Laboratory, a
federal facility in Golden, Colo., said that auto makers are
already developing fuel cells to drive automobiles. Other
researchers, she said, are studying ways of changing the nation's
energy infrastructure _ pipelines, fuel transports and service
stations _ to make use of hydrogen.

   She said it will be at least 20 years before hydrogen becomes a
major part of the energy picture, but the gas could eventually
power the nation, providing a renewable fuel source for both
transportation and electrical generation.

   Right now, hydrogen is most commonly separated from natural gas.
This makes hydrogen a negative in the energy equation, since
natural gas is a cheaper, more efficient fuel.

   Hydrogen may come into its own for environmental reasons, said
Mann.

   Carbon dioxide from the burning of fossil fuels is the primary
cause of global warming, many believe. The only waste generated
from hydrogen fuel is pure water, a resource that theoretically can
be recycled to produce more hydrogen.