Energy - Environmental Science - page 323

We could use electricity from coal-burning and
conventional nuclear power plants to decompose
water into hydrogen and oxygen gas. This approach is
expensive, however, and does not avoid the harmful
environmental effects associated with using these fu-
els (Figures 13-15 and 13-19). We can also make hydro-
gen from coal and strip it from organic compounds
found in fuels such as natural gas (methane),
methanol, and gasoline. However, according to a 2002
study by physicist Marin Hoffer and a team of other
scientists, producing hydrogen from organic com-
pounds will add more CO 2 to the atmosphere per unit
of heat generated than does burning these carbon-con-
taining fuels directly. Using this approach could accel-
erate projected global warming unless we can develop
affordable ways to store (sequester) the CO 2 under-
ground or in the deep ocean.
Most proponents of hydrogen believe that if we
are to receive its very low pollution and low CO 2 emis-
sion benefits, the energy used to produce H 2 by
decomposing water must come from low-polluting,
renewable sources that also emit little or no CO 2 . The
most likely sources are electricity generated by wind
farms, geothermal energy, solar cells, or biological
processes in bacteria and algae (Science Spotlight,
right). Other analysts insist that the best and most effi-
cient ways to reduce the greenhouse gas emissions
from burning coal to produce electricity are to rely
more on renewable wind, hydropower, geothermal en-
ergy, and solar cells to produce electricity instead of
using this energy to produce hydrogen that is then
burned to produce electricity.
In 1999, DaimlerChrysler, Royal Dutch Shell,
Norsk Hydro, and Icelandic New Energy announced
government-approved plans to turn the tiny country
of Iceland, with nearly 300,000 residents, into the
world's first “hydrogen economy” and make the coun-
try self-sufficient in energy by 2050. Hydrogen would
be produced mostly by using Iceland's ample supplies
of hydropower and geothermal energy to produce hy-
drogen from water. The world's first hydrogen fueling
station, built in the capital city of Reykjavik, is supply-
ing hydrogen to power several fuel cell buses. The
next step is to test a fleet of hydrogen-powered cars for
use by corporate or government employees.
Some analysts urge the United States to institute
an Apollo -type program to spur the rapid develop-
ment of a renewable-energy-hydrogen revolution that
would be phased in during the last half of this century.
Once produced, hydrogen can be stored in a pres-
surized tank, as liquid hydrogen, and in solid metal
hydride compounds, which when heated release hy-
drogen gas. Scientists are also evaluating ways to store
H 2 by absorbing it onto the surfaces of activated char-
coal or graphite nanofibers, which when heated re-

Producing Hydrogen
from Green Algae Found
in Pond Scum

In a few decades we may be able
to use large-scale cultures of
green algae to produce hydrogen
gas. This simple plant grows all
over the world and is commonly
found in pond scum.
When living in air and sunlight, green algae
carry out photosynthesis like other plants and pro-
duce carbohydrates and oxygen gas. In 2000, Tasios
Melis, a researcher at the University of California,
Berkeley, found a way to make these algae produce
bubbles of hydrogen rather than oxygen.
First, Melis grew cultures of hundreds of bil-
lions of the algae in the normal way with plenty of
sunlight, nutrients, and water. Then he cut off their
supply of two key nutrients: sulfur and oxygen.
Within 20 hours, the plant cells underwent a meta-
bolic change and switched from an oxygen-pro-
ducing to a hydrogen-producing metabolism, al-
lowing the researcher to collect hydrogen gas bub-
bling from the culture.
Melis believes he can increase the efficiency of
this hydrogen-producing process tenfold. If so,
eventually a biological hydrogen factory might cycle a
mixture of algae and water through a system of
clear tubes exposed to sunlight to produce hydro-
gen. The gene responsible for producing the hydro-
gen might even be transferred to other plants to al-
low them to produce hydrogen.

SCIENCE
SPOTLIGHT

Critical Thinking
What might be some ecological problems related to
the widespread use of this method for producing
hydrogen?

lease hydrogen gas. Another possibility is to store it
inside tiny glass microspheres. Much more research is
needed to convert these dreams into reality.
Some good news. Metal hydrides, charcoal powders,
graphite nanofibers, and glass microspheres contain-
ing hydrogen will not explode or burn if a vehicle's fuel
tank or system is ruptured in an accident. This makes
hydrogen a much safer fuel than the highly volatile
gasoline, diesel fuel, methanol, and natural gas.

x

H OW W OULD Y OU V OTE ? Do the advantages of produc-
ing and burning hydrogen as an energy resource outweigh
the disadvantages? Cast your vote online at http://biology
.brookscole.com/miller11.