Next Generation Biofuel Crops
Using recycled
cooking oil for fuel has yet to become a widespread commercial success, nor is
their enough fryer oil out there to fuel even a fraction of the vehicles in
this country. But in theory, almost any plant material can be converted to
biofuel, including waste products like sawdust and corn stalks (currently
ethanol is made mainly from corn kernels, not stalks). Researchers are working
on biofuels made from species that grow prolifically on marginal land and
require little or no irrigation or fertilizer. Some are even looking to harvest
invasive species as feedstock for biofuel plants.
Unfortunately, a
variety of practical and technological hurdles have prevented large-scale
production of these environmentally-friendly biofuels thus far. But as the
science continues to advance, these challenges are likely to be overcome. Here
are a few of the most promising biofuels currently under development.
Hemp
Hemp fiber has a
long history of use, and the seeds are not only nutritional, but have a
remarkably high oil content. Hemp, essentially a weed, thrives on poor land and
requires minimal inputs, yet produces nearly four times as much oil per acre as soybeans, which is
currently the only crop grown on a large scale for biodiesel in the U.S. The
biggest challenge to using hemp as a biofuel is that so little of it is grown.
Some countries, such as France and Canada, produce it on a limited scale, but
in the U.S. “industrial” hemp has been illegal for farmers to grow since the
1930s—even though it does not contain enough THC to get anyone high.
Switchgrass
While corn-based
ethanol contains scarcely as much energy as is required to produce it, fuel
made from switchgrass, a native prairie plant found in the Great Plains region,
contains more than 5 times as much energy than it takes to grow it and
refine it into ethanol. Rather than tilling up native prairie to plant corn,
switchgrass-based biofuel could encourage replanting of the prairie. The
problem is that “cellulosic” biofuel technology, which is needed to convert
grasses and woody plant materials to ethanol, has not progressed as rapidly as
the technology used to convert grain to fuel. It exists, but it’s not quite
cost-effective yet. Still, several million gallons of cellulosic biofuel are now
produced annually in the U.S., and it seems that it’s only a matter of time
before we have the technology for switchgrass to replace corn as a feedstock
for ethanol.
Carrizo Cane
Hundreds of
thousands of acres in the southern U.S., from Florida to California, are
infested with an exotic plant known as carrizo cane, or giant reed. This
relative of bamboo grows 20 to 30 feet tall in a year’s time, producing more
biomass per acre than almost any other plant on earth. It has been touted as an
even better candidate for cellulosic ethanol production than
switchgrass, and is already being used on a commercial scale in Europe, where
it is a native species, for that purpose. It’s invasive tendencies provide
little incentive to plant it elsewhere, however. There has been some effort
to harvest the carrizo cane already growing in the U.S., which is
found primarily along riverbanks and in wetlands, where it chokes out native
plants. This approach sounds like a win-win, but has proved logistically
infeasible thus far.
Jatropha
This tropical
shrub is poisonous to people and livestock, but the seeds are 40 percent oil,
which was historically used as lamp oil. Starting in mid-2000s, tens of thousands of acres of jatropha were planted for
biofuel, mostly in India and Africa. The plant was known to thrive on marginal
land, but rich soil and irrigation are needed for maximum oil production.
Researchers are continuing to breed improved varieties, however, and several
African countries continue to invest in it, envisioning this scrappy shrub as a
key to their future fuel supply.
Algae
Algae produces up
to 200 times more oil per acre than soy. These fast-growing
aquatic organisms can be grown in salt water, municipal wastewater lagoons, or
in shallow manmade basins in the desert where no other crops can survive. The
U.S. Department of Energy, along with several of the world’s largest oil
companies, have poured hundreds of millions of dollars into scaling up algae
fuel production. A decade ago, industry promoters promised algae fuel would be
as cheap as petroleum fuel by now— and that it would be widely available in gas
stations. But quirks of the plant have made large-scale production
cost-prohibitive, and many algae fuel start-ups have gone under in recent
years. Others are still pursuing the dream. This summer, Exxon Mobil reported a
technological breakthrough that promises to finally make algae fuel
cost-effective—it does, however, involve genetically engineered strain of algae.
