SCIENCE OBSERVER
Grow Your Own?
David Schneider
The nation is abuzz with talk of replacing imported oil with
"biofuels" produced from homegrown materials. This past
April, for example, the U.S. Environmental Protection Agency honored
singer Willie ("On the Road Again") Nelson for his efforts
to promote the use of biodiesel through his "BioWillie"
brand, which is now being distributed at filling stations
nationally. Clearly, many hurdles stand in the way of making such
biofuels commercially competitive with traditional sources. Indeed,
it remains very difficult to forecast whether powering our vehicles
with crop derivatives will ever be a truly economic proposition.
Still, it's not too early to ponder what the widespread adoption of
biofuels would mean for the environment and to take a hard look at
the best strategy available, which may require tapping a very
unconventional crop.
Some back-of-the-envelope calculations are helpful in this regard.
Michael S. Briggs, a biodiesel advocate at the University of New
Hampshire, has estimated that the United States would need about 140
billion gallons of biodiesel each year to replace all the
petroleum-based transportation fuels currently being used. This
calculation is premised on the idea that Americans could over time
switch to using diesel vehicles, as European drivers are clearly
doing. (Half the cars sold in Europe now run on diesel.) Although
one could make a similar appraisal for the amount of biomass-derived
ethanol needed to fill all of our transportation-fuel needs, it
would be unlikely that drivers would ever want to tank up entirely
on ethanol, which contains only two-thirds the energy of gasoline
gallon for gallon, whereas biodiesel (according to Briggs) ends up
being only 2 percent less fuel-efficient than petroleum-based
diesel. Hence a switchover would demand no new technology and would
not significantly reduce the driving range of a car or truck.
The chief feedstock for biodiesel is plant oil derived from one crop
or another. Many candidates have been considered—including
hemp. Perhaps a more reasonable choice is rapeseed oil. An acre of
rapeseed could provide about 100 gallons of biodiesel per
year. To fuel the country this way would thus require 1.4
billion acres of rapeseed fields. This number is a sizable fraction
of the total U.S. land area (2.4 billion acres) and considerably
more than the 400 million or so acres under cultivation in this
country. So the burden on freshwater supplies and the general
disruption that would accompany such a switch in fuel sources would
be immense.
This simple exercise is sobering. It suggests that weaning ourselves
from petroleum fuels and growing rapeseed instead to power the
nation's vehicles would be an environmental catastrophe. Are more
productive oil crops the answer? Oil palms currently top the list
because they can provide enough oil to produce about 500 gallons of
biodiesel per acre per year, which reduces the land requirement
fivefold. Yet its cultivation demands a tropical climate, and its
large-scale production, which currently comes from such countries as
Malaysia and Indonesia, is a significant factor in the ongoing
destruction of what rainforest remains there. Conservationists have
been warning that palm oil production poses a dire threat to the
dwindling population of orangutans, for example, which exist in the
wild only in Borneo and Sumatra. Even the World Bank attributes the
accelerating rate of forest clearing in Indonesia largely to the
establishment of oil-palm plantations. So here again, the prospect
of dedicating sufficient land to growing feedstock for the world's
transportation needs promises to be an environmental nightmare.
There is, however, a "crop" that is widely recognized as
having the potential to meet the demands of a biodiesel-based
transportation fleet without devastating the natural landscape:
algae. Some varieties of these single-celled plants can contain 50
percent or more oil. And they grow much more rapidly than ordinary
cultivars—with doubling times that can be as short as several hours.
The U.S. Department of Energy funded considerable research on
biofuel production using algae after the oil shocks of the 1970s, an
effort known as the Aquatic Species Program. Although this DOE
program was terminated in the mid-1990s, much experience was gained
through research and various demonstration projects. The results
suggested that algae can be grown in sufficient density to provide
for the production of several thousand gallons of biodiesel
per acre per year—a full order of magnitude better than can be
expected using palm oil and two orders of magnitude better than soybeans.
So it is no wonder that many scientists and entrepreneurs are once
again looking hard at the prospects for using algae to produce
transportation fuels. And sizable amounts of money are being
invested in various schemes for doing so. "When Katrina hit and
the price of diesel went to $3.20, that's when the flood gates
opened," says David J. Bayless, a professor of mechanical
engineering at Ohio University in Athens, Ohio.
Bayless and his colleagues have been working with scientists at Oak
Ridge National Laboratory to engineer a device that can grow
cyanobacteria ("blue-green algae"). It uses carbon dioxide
from power-plant flue gases and sunlight that is captured by a
parabolic dish and distributed to the growing surfaces through
optical fibers. With his enclosed bioreactor, Bayless claims to be
able to produce as much as 60 grams of biomass per square meter of
growing surface per day, which is about twice the highest long-term
productivity achieved by the Aquatic Species Program in a
large-scale demonstration in Hawaii using open ponds. Whether
Bayless's system can be scaled up and operated economically remains
to be seen, but some people appear to think there's a possibility:
Manhattan-based Veridium Corporation has licensed this invention in
hopes of commercializing it.
Isaac Berzin, who left MIT to found a Cambridge startup named
GreenFuel Technologies Corporation, is developing algal bioreactors
that would similarly exploit the carbon dioxide coming out of power
plants to fertilize the growth of algae that can then be used to
produce biodiesel. John Lewnard, who is vice president of process
development for GreenFuel, is keenly aware of the challenges
involved in devising a bioreactor that costs little and supports
sufficient productivity that excessive land use is not a factor.
GreenFuel Technologies operated a prototype system at the MIT
cogeneration facility and is currently setting up a more advanced
bioreactor at a natural-gas fired power station at an undisclosed
location in the American Southwest, where having abundant sunlight
for growing algae is presumably less of a problem than in Cambridge.
Lewnard says that productivities of about 100 grams of algae per
meter squared per day (about three times what was demonstrated
during the Aquatic Species Program) is needed to achieve commercial
viability, adding that "we're working very hard to meet that target."
Another recent effort of this type is being carried out by Kent
SeaTech Corporation, which has its headquarters in San Diego. This
company has gained experience growing algae in conjunction with its
striped bass aquaculture operations near California's Salton
Sea. So it was poised to respond when the California state
government started looking for ways to treat the water flowing into
this closed basin, which receives huge quantities of nutrient-laden
runoff from adjacent agricultural lands.
"It's no real difficult feat to turn nutrients into
algae," says Kent SeaTech's director of research, Jon C. Van
Olst, "but how do you get it out of the water? They are almost
impossible to harvest." Van Olst and his coworkers have been
devising ways to enhance the settling of the algae, and they are
currently doing research on turning algal biomass into useful fuel.
Van Olst believes that several separate benefits have to come
together to make growing algae an attractive proposition—the
removal of nutrients from wastewater, the capture of carbon dioxide
that would other otherwise go into the atmosphere, the production of
biodiesel from algal oils and the use of the remaining biomass for
animal feeds. "All those things together might [make] this cost
effective," he says.
The people now working on these and several similar commercial
ventures are clearly eager to make growing algae a going business in
this country. Yet it's not hard to find experts who view such
prospects as dim indeed. John R. Benemann, a private consultant in
Walnut Creek, California, manages the International Network on
Biofixation of CO2 and Greenhouse Gas Abatement with
Microalgae for the International Energy Agency. He helped author the
final report of the Aquatic Species Program and has decades of
experience in this field. "Growing algae is cheap," he
says, but "certainly not as cheap as growing palm oil."
And he is particularly skeptical about attempts to make algal
production more economical by using enclosed bioreactors (rather
than open ponds, as were used for the Aquatic Species Program). He
points out that Japan spent hundreds of millions of dollars on such
research, which never went anywhere. Asked to comment about why
there is so much effort in that direction now, he responds,
"It's bizarre; it's totally absurd."
Even more telling is the reaction of Gerald R. Cysewski, president
and chief executive officer of Cyanotech Corporation, a Hawaii
company that grows algae for sale as a food supplement. Cysewski,
who holds a doctorate in chemical engineering from UC Berkeley, is
no stranger to the biofuels concept: For his Ph.D. (which he earned
more than two decades ago), he studied the enzymatic production of
ethanol from cellulose. Yet he has turned down recent offers to
collaborate on projects to use algae for producing biofuels,
preferring to keep his business focused on products that sell
anywhere from $18 to $380 per kilogram (fuel oil, he points out,
goes for something like 45 cents per kilogram). "In the
laboratory, you can create some very efficient bioreactors, but it
just isn't scalable," he says. Asked whether biodiesel will
ever be made this way, he responds: "Not from
microalgae—I just can't see it."
Even Kent SeaTech's Van Olst has serious reservations. "I'd put
myself in with the skeptics," he says. "It may work, but
it's going to take a while and a lot of research before we get anywhere."
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