>From the University ofCalif @ Berkeley....
########
BERKELEY-- A metabolic switch that triggers algae to turn sunlight into
large quantities of hydrogen gas, a valuable fuel, is the subject of a new
discovery reported for the first time by University of California, Berkeley,
scientists and their Colorado colleagues. The news appears in this month's
issue of the journal "Plant Physiology."
"I guess it's the equivalent of striking oil," said UC Berkeley plant and
microbial biology professor Tasios Melis. "It was enormously exciting, it was
unbelievable."
Melis and postdoctoral associate Liping Zhang of UC Berkeley made the
discovery - funded by the U.S. Department of Energy (DOE) Hydrogen Program -
with Dr. Michael Seibert, Dr. Maria Ghirardi and postdoctoral associate Marc
Forestier of the National Renewable Energy Laboratory (NREL) in Golden,
Colorado.
Currently, hydrogen fuel is extracted from natural gas, a non-renewable
energy source. The new discovery makes it possible to harness nature's own
tool, photosynthesis, to produce the promising alternative fuel from sunlight
and water. A joint patent on this new technique for capturing solar energy
has been taken out by the two institutions.
So far, only small-scale cultures of the microscopic green alga Chlamydomonas
reinhardtii have been examined in the laboratory for their hydrogen
production capabilities, Melis said.
"In the future, both small-scale industrial and commercial operations and
larger utility photobioreactor complexes can be envisioned using this
process," Melis said.
While current production rates are not high enough to make the process
immediately viable commercially, the researchers believe that yields could
rise by at least 10 fold with further research, someday making the technique
an attractive fuel-producing option.
Preliminary rough estimates, for instance, suggest it is conceivable that a
single, small commercial pond could produce enough hydrogen gas to meet the
weekly fuel needs of a dozen or so automobiles, Melis said.
The scientific team is just beginning to test ways to maximize hydrogen
production, including varying the particular type of microalga used and its
growth conditions.
Many energy experts believe hydrogen gas one day could become the world's
best renewable source of energy and an environmentally friendly replacement
for fossil fuels.
"Hydrogen is so clean burning that what comes out of the exhaust pipe is pure
water," Melis said. "You can drink it."
Engineering advances for hydrogen storage, transportation and utilization,
many sponsored by the U.S. DOE Hydrogen Program, are beginning to make the
fuel feasible to power automobiles and buses and to generate electricity in
this country, Seibert said.
"What has been lacking is a renewable source of hydrogen," he said.
For nearly 60 years, scientists have known that certain types of algae can
produce the gas in this way, but only in trace amounts. Despite tinkering
with the process, no one has been able to make the yield rise significantly
without elaborate and costly procedures until the UC Berkeley and NREL teams
made this discovery.
The breakthrough, Melis said, was discovering what he calls a "molecular
switch." This is a process by which the cell's usual photosynthetic apparatus
can be turned off at will and the cell can be directed to use stored energy
with hydrogen as the byproduct.
"The switch is actually very simple to activate," Melis said. "It depends on
the absence of an essential element, sulfur, from the microalga growth
medium."
The absence of sulfur stops photosynthesis and thus halts the cell's internal
production of oxygen. Without oxygen from any source, the anaerobic cells are
not able to burn stored fuel in the usual way, through metabolic respiration.
In order to survive, they are forced to activate the alternative metabolic
pathway, which generates the hydrogen and may be universal in many types of
algae.
"They're utilizing stored compounds and bleeding hydrogen just to survive,"
Melis said. "It's probably an ancient strategy that the organism developed to
live in sulfur-poor anaerobic conditions."
He said the alga culture cannot live forever when it is switched over to
hydrogen production, but that it can manage for a considerable period of time
without negative effects.
The researchers first grow the alga "photosynthetically like every other
plant on Earth," Melis said. This allows the green-colored microorganisms to
collect sunlight and accumulate a generous supply of carbohydrates and other
fuels.
When enough energy has been banked in this manner, the researchers tap it and
turn it into hydrogen. To do this, they transfer the liquid alga culture,
which resembles a lime-green soft drink, to stoppered one-liter glass bottles
with no sulfur present. Then the culture is allowed to consume away all
oxygen.
After about 24 hours, photosynthesis and normal metabolic respiration stop,
and hydrogen begins to bubble to the top of the bottles and bleed off into
tall, hydrogen-collection glass tubes.
"It was actually a surprise when we detected significant amounts of hydrogen
coming out of the culture," Melis said. "We thought we would get trace
amounts, but we got bulk amounts."
After up to four days of generating an hourly average of about three
milliliters of hydrogen per liter of culture, the culture is depleted of
stored fuel and must be allowed to return to photosynthesis. Then, two or
three days later, it again can be tapped for hydrogen, Melis said.
"The cell culture can go back and forth like this many times," Ghirardi said.
###
Kinda neat in my opinion...
A couple of observations here. Hydrogen gas (and propane and methane)
require a LOT of room to store....hence all the 'work arounds" involving
liquidification and hi pressurization. This is a bad thing for small
vehicles.
However...it's not such a bad thing for large vehicles. Does this mean that
"heavy metal" of the future will be even larger?
Right now my rig is seventy foot long by 102 inches wide....I regularly carry
oversize loads of up to 14 foot high by 12 foot wide. If the infra structure
were to be slightly modified then a very large hydrogen fuel tank for rigs
similar to mine would not be overly difficult.
Just wider roads and bigger parking area's is all....
EvMick
houston Tx.
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:04:02 MDT