Ethanol Fuel Energy Balance
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OR:

† depending on production method
In order to create ethanol, all
biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
needs to go through some of these steps: it needs to be grown, collected, dried, fermented, and burned. All of these steps require resources and an infrastructure. The ratio of the energy released by burning the resulting
ethanol fuel Ethanol fuel is fuel containing ethyl alcohol, the same type of alcohol as found in alcoholic beverages. It is most often used as a motor fuel, mainly as a biofuel additive for gasoline. Several common ethanol fuel mixtures are in use aro ...
to the energy used in the process, is known as the ethanol fuel energy balance (sometimes called " Net energy gain") and studied as part of the wider field of
energy economics Energy economics is a broad scientific subject area which includes topics related to supply and use of energy in societies. Considering the cost of energy services and associated value gives economic meaning to the efficiency at which energy ...
. Figures compiled in a 2007
National Geographic Magazine ''National Geographic'' (formerly ''The National Geographic Magazine'', sometimes branded as ''Nat Geo'') is an American monthly magazine published by National Geographic Partners. The magazine was founded in 1888 as a scholarly journal, nine ...
article point to modest results for corn (maize) ethanol produced in the US: 1 unit of energy input equals 1.3 energy units of corn ethanol energy. The energy balance for sugarcane ethanol produced in Brazil is much more favorable, 1 to 8. Over the years, however, many reports have been produced with contradicting energy balance estimates. A 2006 University of California Berkeley study, after analyzing six separate studies, concluded that producing ethanol from corn uses marginally less petroleum than producing gasoline.Sanders, Robert (January 26, 2006
Ethanol can replace gasoline with significant energy savings, comparable impact on greenhouse gases
''University of California Berkeley'' Energy Resources Group, Dan Kammen and Alex Farrell; Michael O'Hare, Goldman School of Public Policy. Also published 27 JANUARY 2006 VOL 311 Science, www.sciencemag.org .Retrieved August 22, 2011.


Energy balance reports

In 1995 the
USDA The United States Department of Agriculture (USDA) is an United States federal executive departments, executive department of the Federal government of the United States, United States federal government that aims to meet the needs of commerc ...
released a report stating that the net energy balance of corn ethanol in the United States was an average of 1.24. It was previously considered to have a negative net energy balance. However, due to increases in corn crop yield and more efficient farming practices corn ethanol had gained
energy efficiency Energy efficiency may refer to: * Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process ** Electrical efficiency, useful power output per electrical power consumed ** Mechanical efficiency, a rat ...
. Ken Cassman, a professor of agronomy at the
University of Nebraska–Lincoln The University of Nebraska–Lincoln (Nebraska, NU, or UNL) is a Public university, public Land-grant university, land-grant research university in Lincoln, Nebraska, United States. Chartered in 1869 by the Nebraska Legislature as part of the M ...
, said in 2008 that ethanol has a substantial net positive direct energy balance: 1.5 to 1.6 more units of energy are derived from ethanol than are used to produce it. Comparing 2008 to 2003, Alan Tiemann of Seward, a Nebraska Corn Board member, said that ethanol plants produce 15 percent more ethanol from a bushel of corn and use about 20 percent less energy in the process. At the same time, corn growers are more efficient, producing more corn per acre and using less energy to do so. Opponents of corn ethanol production in the U.S. often quote the 2005 paper of David Pimentel, a retired Entomologist, and Tadeusz Patzek, a Geological Engineer from UC Berkeley. Both have been exceptionally critical of ethanol and other biofuels. Their studies contend that ethanol, and biofuels in general, are "energy negative", meaning they take more energy to produce than is contained in the final product. A 2006 article in
Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
offers the consensus opinion that current corn ethanol technologies had similar greenhouse gas emissions to gasoline, but was much less petroleum-intensive than gasoline.
Fossil fuels A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geologica ...
also require significant energy inputs which have seldom been accounted for in the past. Ethanol is not the only product created during production. By-products also have energy content. Corn is typically 66% starch and the remaining 33% is not fermented. This unfermented component is called distillers grain, which is high in fats and proteins, and makes a good animal feed supplement. In 2000, Dr. Michael Wang, of
Argonne National Laboratory Argonne National Laboratory is a Federally funded research and development centers, federally funded research and development center in Lemont, Illinois, Lemont, Illinois, United States. Founded in 1946, the laboratory is owned by the United Sta ...
, wrote that these ethanol by-products are the most contentious issue in evaluating the energy balance of ethanol. He wrote that Pimentel assumes that corn ethanol entirely replaces gasoline and so the quantity of by-products is too large for the market to absorb, and they become waste. At lower quantities of production, Wang finds it appropriate to credit corn ethanol based on the input energy requirement of the feed product or good that the ethanol by-product displaces. In 2004, a USDA report found that co-products accounting made the difference between energy ratios of 1.06 and 1.67. In 2006, MIT researcher Tiffany Groode came to similar conclusions about the co-product issue. In Brazil where sugar cane is used, the yield is higher, and conversion to ethanol is more energy efficient than corn. Recent developments with
cellulosic ethanol Cellulosic ethanol is ethanol (ethyl alcohol) produced from cellulose (the stringy fiber of a plant) rather than from the plant's seeds or fruit. It can be produced from grasses, wood, algae, or other plants. It is generally discussed for use as a ...
production may improve yields even further. In 2006 a study from the
University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...
found that corn-grain ethanol produced 1.25 units of energy per unit put in. A 2008 study by the
University of Nebraska A university () is an educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...
found a 5.4 energy balance for ethanol derived specifically from
switchgrass ''Panicum virgatum'', commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55th parallel north, 55°N latitude in Canada southwards into the United States and Mexico. Switch ...
. This estimate is better than in previous studies and according to the authors partly due to the larger size of the field trial (3-9 ha) on 10 farms.


Variables

According to DoE, to evaluate the net energy of ethanol four variables must be considered: # the amount of energy contained in the final ethanol product # the amount of energy directly consumed to make the ethanol (such as the diesel used in
tractors A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a Trailer (vehicle), trailer or machinery such as that used in agriculture, mining or constructio ...
) # the quality of the resulting ethanol compared to the quality of refined gasoline # the energy indirectly consumed (in order to make the ethanol processing plant, etc.). Much of the current academic discussion regarding ethanol currently revolves around issues of system borders. This refers to how complete a picture is drawn for energy inputs. There is debate on whether to include items like the energy required to feed the people tending and processing the corn, to erect and repair farm fences, even the amount of energy a tractor represents. In addition, there is no consensus on what sort of value to give the rest of the corn (such as the stalk), commonly known as the 'coproduct.' Some studies leave it on the field to protect the soil from erosion and to add organic matter, while others take and burn the coproduct to power the ethanol plant, but do not address the resulting soil erosion (which would require energy in the form of fertilizer to replace). Depending on the ethanol study you read, net energy returns vary from .7-1.5 units of ethanol per unit of fossil fuel energy consumed. For comparison, that same one unit of fossil fuel invested in oil and gas extraction (in the lower 48 States) will yield 15 units of gasoline, a yield an order of magnitude better than current ethanol production technologies, ignoring the energy quality arguments above and the fact that the gain (14 units) is both declining and not carbon neutral. In this regard,
geography Geography (from Ancient Greek ; combining 'Earth' and 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding o ...
is the decisive factor. In tropical regions with abundant water and land resources, such as
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
and
Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
, the viability of production of ethanol from
sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...
is no longer in question; in fact, the burning of sugar-cane residues (
bagasse Bagasse ( ) is the dry pulpy fibrous material that remains after crushing sugarcane or sorghum stalks to extract their juice. It is used as a biofuel for the production of heat, energy, and electricity, and in the manufacture of pulp and building ...
) generates far more energy than needed to operate the ethanol plants, and many of them are now selling electric energy to the utilities. However, while there may be a positive net energy return at the moment, recent research suggests that the sugarcane plantations are not sustainable in the long run, as they are depleting the soil of nutrients and carbon matter On the other hand, productivity of sugar cane per land area in Brazil has consistently grown over the decades; sugar cane has been shown to be less depleting to the soil than cattle and yearly cultures; and there are many regions in the country where sugar cane has been cultivated for centuries. Those facts suggest that related soil depletion processes are very slow and therefore ethanol from sugar cane may be far more sustainable in the long run than common fossil fuel alternatives. Besides, since the energy surplus is high in the case of sugar-cane ethanol, conceivably part of that energy can be used to synthesize fertilizers and replenish soil depletion over a long time, therefore making the process indefinitely sustainable. The picture is different for other regions, such as most of the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, where the climate is too cool for sugar cane. In the U.S., agricultural ethanol is generally obtained from
grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...
, chiefly
corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...
. But it can also be obtained from
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
, a more energy balanced bioethanol.


Clean production bioethanol

Clean production bioethanol INEOS Bio: Bioethanol: Sustainability
Quote: "An independent
life-cycle assessment Life cycle assessment (LCA), also known as life cycle analysis, is a methodology for assessing the impacts associated with all the stages of the life cycle of a commercial product, process, or service. For instance, in the case of a manufact ...
carried out by Eunomia on the production of INEOS Bio Ethanol from waste biomass indicates that greenhouse-gas savings of more than 90% vs. gasoline could be achieved... This saving is significantly higher than the best performing bioethanol today, which is sugar-cane ethanol made in Brazil, (reported to deliver up to 70% greenhouse-gas savings)." date=July 2011
is a biofuel obtained by maximizing non-
greenhouse gas Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
emitting (renewable) resources: * energy directly consumed to make the ethanol is
renewable energy Renewable energy (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...
. The farm equipment and ethanol plant use an ethanol engine,
biodiesel Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats. The roots of bi ...
, air engine or electricity cogenerated during ethanol production, or even
wind power Wind power is the use of wind energy to generate useful work. Historically, wind power was used by sails, windmills and windpumps, but today it is mostly used to generate electricity. This article deals only with wind power for electricity ge ...
and
solar energy Solar energy is the radiant energy from the Sun's sunlight, light and heat, which can be harnessed using a range of technologies such as solar electricity, solar thermal energy (including solar water heating) and solar architecture. It is a ...
. * energy indirectly consumed is, as much as possible, renewable. Examples would be reducing either the amount or fossil carbon content of applied pest control chemicals and fertilizers, or accomplishing deliveries of farm inputs or of finished bioethanol fuel to market that minimize the use of fossil fuels. Optimally located biomass and ethanol production must balance many factors: minimizing distances to and from markets, effectively collecting and employing biomass wastes, maximizing crop yields based on enduring
soil quality Soil quality refers to the condition of soil based on its capacity to perform ecosystem services that meet the needs of human and non-human life.Tóth, G., Stolbovoy, V. and Montanarella, 2007. Soil Quality and Sustainability Evaluation - An integ ...
, available natural pest control and adequate sun and water, and optimizing a sufficient mix and rotation of plant species on cultivated, fallow, and preserved land for human, animal, and energy consumption. Using ethanol returns carbon to the atmosphere whereas burning gasoline adds carbon to the atmosphere. Thus the effects of gasoline burning increase over time.


See also

*
Biobutanol image:Butanol_flat_structure.png, Butanol, a C-4 hydrocarbon is a promising bio-derived fuel, which shares many properties with gasoline. Butanol may be used as a fuel in an internal combustion engine. It is more similar to gasoline than it is to ...
*
Energy returned on energy invested In energy economics and ecological energetics, energy return on investment (EROI), also sometimes called energy returned on energy invested (ERoEI), is the ratio of the amount of usable energy (the '' exergy'') delivered from a particular energy ...
*
Starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...


References

{{DEFAULTSORT:Ethanol Fuel Energy Balance Ethanol fuel Environmental impact of the energy industry