Bioetanol

Bioethanol

Fueling Sustainable Transportation

s

What is Bioethanol?

s

A domestically produced liquid fuel made from renewable plant
resources known as biomass
A renewable transportation fuel whose production contributes
only small amounts of fossil-derived carbon dioxide (CO2)
to the Earth’s atmosphere
A high-octane fuel that can contribute substantially to the
U.S.automotive fuel supply
A fuel that can be used in a blend with gasoline or neat
(95% ethanol with a denaturant), with excellent efficiency and
performance
A clean-burning fuel that reduces urban air pollution.

s

s

s

s

s

Availability of biomass
materials on a sustainable
basis exceeds 200 million
tons annually—enough for
20 billion gallons of
ethanol each year.

The ResourceToday, most U.S. ethanol production is based in
the grain-growing states of the Midwest, where
over 500 million bushels of corn and other
starch crops are used as feedstocks to produce
approximately 1.4 billion gallons of ethanol
annually. At about 1.1% of U.S. gasoline consumption, ethanol represents a small percentage
of our total transportation fuel supply. But
demand is growing for thisalternative to petroleum, and for ethanol production
to keep up with increasing
demand, feedstock supplies for
the fuel must also keep pace. To
meet this need, the U.S. Department of Energy (DOE) is, in conjunction with private industry,
developing ways to use abundant, low-cost cellulosic biomass.
Plentiful, domestic, cellulosic
biomass feedstocks such as
herbaceous and woody plants,agricultural and forestry residues, and a large portion of many municipal solid waste and industrial
waste streams, can be converted to ethanol.
Availability of these materials on a sustainable
basis exceeds 200 million tons annually—enough
for 20 billion gallons of ethanol each year.
Because corn cobs, leaves, and stalks are made
of cellulosic material, these research efforts will
alsoallow the corn industry to use parts of the
corn plant that are now waste, and expand
beyond the limits of starch-derived ethanol.

Agricultural by-products such as corn stover can now be
used as feedstock for making bioethanol.

s

Making fuels from biomass involves a variety of
thermal, chemical, and
biological processes.

Cellulosic biomass is a
complex mixture of cellulose,hemicellulose,
lignin, and extractives.
To produce ethanol from
biomass, the cellulose
and hemicellulose portions must be broken
down into simple sugars
and the sugars must be
fermented to ethyl alcohol or ethanol.

The Process

Cellulosic biomass is a complex mixture of plant
cell wall carbohydrate polymers known as cellulose and hemicellulose, plus lignin and a smaller
amount of othercompounds known as extractives. To produce ethanol from biomass feedstocks, two key processes must occur. First, the
hemicellulose and cellulose portions of the biomass must be broken down into simple sugars
through a process called saccharification. Second, the sugars must be fermented to make ethyl
alcohol or ethanol. A variety of thermal, chemical, and biological processes can be used to produceethanol from biomass. Several U.S. research
organizations and companies are exploring combinations of these processes to develop the most
efficient and economical route for the commercial production of ethanol.

Biomass Composition

Cellulose
(Glucose sugar)
45%

Other
5%
Lignin
25%

Hemicellulose
(Pentose sugars)
25%

s

Utilization

The Clean Air Act Amendments of 1990mandated the sale of oxygenated fuels in areas of
the country with unhealthy levels of carbon
monoxide. Since that time there has been strong
demand for ethanol as an oxygenate blended
with gasoline. Several ethanol blends have been
tested, and some are being distributed by service
stations throughout the United States. E10 (10%
ethanol, 90% gasoline) is the most commonly
distributed, with...