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|Ethanol can be produced from a wide variety of
plant-based feedstocks, most commonly grain or sugar crops. It
is then blended with gasoline as an oxygenate or fuel extender
for use in gasoline vehicles, or it can be used alone in “flexible-fuel
vehicles” that run on any blend of ethanol and gasoline.
Brazil led world ethanol production in 2004, distilling four
billion gallons (15 billion liters). The United States is rapidly
catching up, however, producing 3.5 billion gallons last year,
almost exclusively from corn. China's wheat- and corn-rich provinces
produced nearly one billion gallons of ethanol, and India turned
out 500 million gallons made from sugarcane.
France, the front-runner in the European Union’s attempt
to boost ethanol use, produced over 200 million gallons from
sugar beets and wheat. In all, the world produced enough ethanol
to displace roughly two percent of total gasoline consumption.
(For more examples of ethanol production by country, see data
Efforts to substitute alternative fuels for petroleum are gaining
attention in a world threatened by climate change, rural economic
decline, and instability in major oil-producing countries. Biofuel
crops take in carbon dioxide from the atmosphere while they are
growing, offsetting the greenhouse gases released when the fuel
is subsequently burned. Replacing petroleum with biofuel can
reduce air pollution, including emissions of fine particulates
and carbon monoxide. Biofuel production also can improve rural
economies by creating new jobs and raising farm incomes. As a
locally produced, renewable fuel, ethanol has the potential to
diversify energy portfolios, lower dependence on foreign oil,
and improve trade balances in oil-importing nations.
Although ethanol’s popularity is growing, today’s
inefficient production methods and conversion technologies mean
that this fuel will only produce modest environmental and economic
benefits and could impinge on international food security. The
largest obstacle to biofuel production is land availability.
Expanding cropland for energy production will likely worsen the
already intense competition for land between agriculture, forests,
and urban sprawl. With temperatures rising and water tables falling
worldwide, global food supply and demand are precariously balanced.
World grain reserves are near all-time lows, and there is little
idle cropland to be brought back into cultivation. Shifting food
crops to fuel production could further tighten food supplies
and raise prices, pitting affluent automobile owners against
low-income food consumers.
Placing greater emphasis on land efficiency—that is, maximizing
energy yield per acre—will be essential to making the best
use of ethanol. Though corn has broad political support as a
feedstock in the United States, it is one of the least efficient
sources of ethanol. For example, ethanol yields per acre for
French sugar beets and Brazilian sugarcane are roughly double
those for American corn.
Also important is the amount of energy used to produce ethanol.
Growing, transporting, and distilling corn to make a gallon of
ethanol uses almost as much energy as is contained in the ethanol
itself. Sugar beets are a better source, producing nearly two
units of energy for every unit used in production. Sugarcane,
though, is by far the most efficient of the current feedstocks—yielding
eight times as much energy as is needed to produce the ethanol.
Given their positive energy balances and higher yields, it makes
more sense to produce ethanol from sugar crops than from grains.
Ethanol could quickly take off in sugarcane-producing tropical
countries, which have the advantage of year-round growing seasons,
large labor supplies, and low production costs. As fuel demand
rises in these developing nations, biofuel production could check
oil imports while bolstering rural economies. Brazil, for example,
could produce enough ethanol to meet total domestic fuel demand
by increasing the area used to grow sugarcane for alcohol from
6.6 million acres to 13.8 million acres (5.6 million hectares)
or by shifting all current sugarcane acreage to ethanol production.
Unfortunately, new fields may cut further into already shrinking
rainforests, making them a serious environmental liability.
If ethanol is to become a major part of the world fuel supply
without competing with food and forests, it’s primary source
will not be grains or even sugar crops; it will be more-abundant
and land-efficient cellulosic feedstocks, such as agricultural
and forest residues, grasses, and fast-growing trees. Promising
new technologies are being developed that use enzymes to break
down cellulose and release the plants’ sugars for fermentation
into ethanol. A demonstration plant using this technology opened
in Canada last year, and large-scale production is expected to
be commercially viable by 2015.
Agricultural residues, such as corn stalks, wheat straw, and
rice stalks, are normally left on the field, plowed under, or
burned. Collecting just a third of these for biofuel production
would allow farmers to reap a sort of second harvest, increasing
farm income while leaving enough organic matter to maintain soil
health and prevent erosion. The agricultural residues that could
be harvested sustainably in the United States today, for example,
could yield 14.5 billion gallons of ethanol—four times
the current output—with no additional land demands.
Energy crops,” such as hardy grasses and fast-growing trees,
have higher ethanol yields and better energy balances than conventional
starch crops. One likely candidate is switchgrass, a tall perennial
grass used by farmers to protect land from erosion. It requires
minimal irrigation, fertilizer, or herbicides but yields two
to three times more ethanol per acre than corn does. Such crops
could potentially be harvested on marginal land, avoiding the
conversion of healthy cropland or forests to energy-crop production.
Still, with world energy demands rising, biofuels will meet only
a fraction of fuel needs unless there are substantial improvements
in vehicle fuel economy. Fortunately, the technologies required
are available and affordable. Shifting vehicle production to
gas-electric hybrids, like those on the market today, and reducing
weight and drag would decrease fuel use several fold. Adding
an extra battery and plug-in capability to hybrid vehicles would
allow short trips to be made using only electric power – preferably
produced from wind – decreasing fuel demand to levels that
could be met with ethanol alone.
Increasing the role of ethanol in meeting fuel demand will require
ongoing research and development to improve biomass-ethanol conversion
technologies, along with consistent legislative support for biofuel
production and greater fuel efficiency in the automotive industry.
Shifting government energy subsidies, such as from oil exploration
to biofuel development, is a clear choice as new oil fields prove
increasingly elusive. With improved vehicle fuel economy and
the use of more-efficient cellulosic feedstocks, biofuel has
the potential to supply a substantial share of the world’s
Additional data and information sources at www.earth-policy.org
or contact dmurray (at) earth-policy.org.
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