By C. Kohn
Agricultural Sciences
Waterford, WI
Unless specially cited, all information is taken from the Alternative Fuels and Advanced Vehicles Data
Center and the Great Lakes Bioenergy Research Center, both of the US Department of Energy.
Ethanol
 Ethanol is a liquid produced by yeast through
fermentation, or the conversion of sugars and other
carbohydrates into ethanol and carbon dioxide in the
absence of oxygen.
 Pure ethanol is a clear, colorless liquid that consists of
2 carbon atoms bonded to a hydroxyl (-OH) group
 Ethanol has the same molecular
structure (CH3CH2OH)
regardless its original source
(corn, sugar cane, etc.)
Ethanol and Engines
 Ethanol works well in internal combustion engines.
 Henry Ford and other early automakers thought ethanol
would be the world's primary fuel before gasoline became
so readily available.
 Unfortunately, a gallon of pure
ethanol (E100) contains 34%
less energy than a gallon of gasoline.
 However, ethanol does have a higher
octane rating, improving engine
performance.
Ethanol as a Fuel
 Ethanol is a high-octane fuel.
 The octane rating is a measure of how efficiently a fuel combusts.
 Low-octane gasoline can be blended with 10% ethanol to attain the
standard 87 octane requirement.
 Low-level blends of ethanol, such as E10 (10% ethanol, 90% gasoline),
generally have a higher octane rating than unleaded gasoline.
 This means that the addition of ethanol to gasoline generally tends to
improve engine performance by increasing the octane rating of the fuel.
Ethanol Benefits
 Ethanol is a renewable, largely domestic transportation fuel.
 Use of ethanol and other alternative fuels can displace a
significant amount of imported petroleum.
 About two-thirds of U.S. petroleum demand is used for
transportation.
 60% of U.S. petroleum is currently imported.
 Ethanol use also supports the U.S. agricultural sector and
improves the US economy by providing jobs and investment
opportunities.
Reducing GHGs
 The carbon dioxide released when ethanol is burned is balanced
by the carbon dioxide captured when the crops are grown to
make ethanol.
 This differs from petroleum, which is made from plants that grew
millions of years ago and obviously do not reabsorb CO2 after it is
emitted.
 According to Argonne National Laboratory, on a life-cycle
analysis basis, corn-based ethanol production and use reduces
greenhouse gas emissions (GHGs) by up to 52% compared to
gasoline production and use.
 Cellulosic ethanol use could reduce GHGs by as much as 86%.
Protecting the Environment
 Ethanol is biodegradable and, if spilled,
poses much less of a threat than
petroleum to surface and ground water.
 E.g. after the sinking of the Bow
Mariner off the Virginia coast in
February 2004, U.S. Coast Guard
officials noted the cargo of 3.2 million
gallons of industrial ethanol had
dissipated quickly and did not pose an
environmental threat to humans or
marine life.
 Compare this to the 2010 oil spill in the
Gulf of Mexico!
Sources of Ethanol
 Ethanol can be produced from a variety
of sources.
 Ethanol produced in Brazil is made
primarily from sugar cane.
 Ethanol produced in the US is made
primarily from corn.
 The original source of ethanol, or its
feedstock, is a major determining factor
in its ease of production and
sustainability.
Feedstock Comparison
 Sugar Cane
 (+) easiest to ferment into ethanol
 (-) cannot be grown in most of the US (not a domestic fuel)
 Corn (grain)
 (+) widely available; grown in all 50 states
 (-) competition for food; not enough corn grain to meet all US
energy needs; choice of cultivation methods can have major
impacts on the sustainability of this feedstock
 Cellulose (plant stalks, leaves, trunks, branches, and husks)
 (+) found everywhere we find plants; large supply; very sustainable;
can be waste material from other crops or grown on marginal lands
 (-) most difficult to ferment into ethanol
Source: donhavey.com
Cellulosic Feedstocks
 Cellulosic feedstocks have many advantages over starch-
and sugar-based feedstocks.
 They are much more abundant and thus can be used to
produce more substantial amounts of ethanol to meet U.S.
fuel demand.
 Cellulosic feedstocks are usually either waste products (such
as the corn stover that remains after the corn cobs themselves
are harvested) or can be grassy crops that are grown on lowquality land (such as prairie or switchgrass)
 Less fossil fuel energy is required to grow/collect them and
convert them to ethanol, and they are not human food
products (meaning they won’t raise food prices).
Source: donhavey.com
Cellulosic Feedstocks
 Cellulosic feedstocks suited to ethanol production include
the following:
 Agricultural residue —crop residues such as wheat straw and




corn stalks, leaves, and husks
Forestry residue —logging and mill residues such as wood
chips, sawdust, and pulping liquor
Grasses —hardy, fast-growing grasses such as switchgrass
grown specifically for ethanol production
Municipal and other wastes—plant-derived wastes such as
household garbage, paper products, paper pulp, and foodprocessing waste
Trees—fast-growing trees such as poplar and willow grown
specifically for ethanol production
Source: donhavey.com
Ethanol Myths and Facts
 True or False? Discuss in groups; be ready to present:
1. In terms of emissions, ethanol pollutes the same as gasoline or
2.
3.
4.
5.
more.
Ethanol cannot be produced from corn in large enough
quantities to make a real difference without disrupting food
and feed supplies.
More energy goes into producing ethanol than it delivers as a
fuel.
Ethanol-gasoline blends can lower fuel economy and may
harm your engine.
Rainforests will be destroyed to create the new croplands
required to meet food, feed, and biofuels needs, thus
accelerating climate change and destroying valuable
ecosystems.
In terms of emissions, ethanol pollutes the same
as gasoline or more.
 Myth!
 Ethanol produced from corn results in about a
20% reduction in GHG emissions compared to
gasoline
 Ethanol produced from cellulose has the potential to
cut life cycle GHG emissions by up to 86
percent relative to gasoline.
Ethanol cannot be produced from corn in large enough
quantities to make a real difference without disrupting
food and feed supplies.
 ½ Myth, ½ Fact
 Corn grain ethanol, by itself, is not enough to meet US
energy needs
 However, corn is not the only source of ethanol!
 Future ethanol will be produced increasingly from
cellulose, energy crops (e.g., switchgrass, sorghum), and
sorted municipal wastes.
 The Energy Independence and Security Act of 2007 (EISA)
requires use of 36 billion gallons of renewable
transportation fuels in the U.S. by 2022.
 Of that quantity, 16 billion gallons must be cellulosic biofuels.
 Ethanol from corn is capped at 15 billion gallons
More energy goes into producing ethanol than it
delivers as a fuel.
 Myth!
 Ethanol has a positive energy balance – that is, the
energy content of ethanol is greater than the fossil
energy used to produce it
 Plus, this balance is
constantly improving
with new technologies.
Ethanol-gasoline blends can lower fuel economy
and may harm your engine.
 ½ Myth, ½ Fact
 Flex-fuel vehicles designed to run on higher ethanol blends
(E85 or 85 percent ethanol) do experience reduced miles
per gallon.
 However, they also show a significant gain in horsepower.
 Ethanol enhances engine performance and adds oxygen,
increasing the octane rating of fuel.
Rainforests will be destroyed to create the new croplands
required to meet food, feed, and biofuels needs, thus
accelerating climate change and destroying valuable ecosystems.
 Pending, but probably Myth
 Bottom-line: regulations and economic incentives will be
necessary to ensure that a fuel adopted for reasons of
sustainability will actually be sustainable.
 This hinges on whether we can continue to increase our use of
cellulosic sources of ethanol and whether or not farmers can
merge sustainable practices with new crops
 E.g. the planting and harvesting of diverse prairie could provide
additional wildlife habitat while simultaneously providing a
perennial feedstock for ethanol.
 A top focus of US energy research is sustainability (e.g. GLBRC)