Ethanol fuel energy balance

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Energy balance [1]
CountryTypeEnergy balance
Flag of the United States (23px).png  United States Corn ethanol1.3
Flag of Brazil.svg  Brazil Sugarcane ethanol8
Flag of Germany.svg  Germany Biodiesel2.5
Flag of the United States (23px).png  United States Cellulosic ethanol†2–36

† depending on production method

In order to create ethanol, all biomass 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 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. Figures compiled in a 2007 National Geographic Magazine article [1] 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. [2]

Contents

Energy balance reports

In 1995 the USDA 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. [3]

Ken Cassman, a professor of agronomy at the University of Nebraska–Lincoln, 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. [4]

Opponents of corn ethanol production in the U.S. often quote the 2005 paper [5] 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 [6] in Science 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 also require significant energy inputs which have seldom been accounted for in the past.[ citation needed ]

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. [7]

In 2000, Dr. Michael Wang, of Argonne National Laboratory, 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. [8] In 2004, a USDA report found that co-products accounting made the difference between energy ratios of 1.06 and 1.67. [9] [10] In 2006, MIT researcher Tiffany Groode came to similar conclusions about the co-product issue. [11]

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 production may improve yields even further. [12]

In 2006 a study from the University of Minnesota found that corn-grain ethanol produced 1.25 units of energy per unit put in. [13]

A 2008 study by the University of Nebraska found a 5.4 energy balance for ethanol derived specifically from switchgrass. [14] [15] 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, [16] to evaluate the net energy of ethanol four variables must be considered:

  1. the amount of energy contained in the final ethanol product
  2. the amount of energy directly consumed to make the ethanol (such as the diesel used in tractors)
  3. the quality of the resulting ethanol compared to the quality of refined gasoline
  4. 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. [17]

In this regard, geography is the decisive factor. In tropical regions with abundant water and land resources, such as Brazil and Colombia, the viability of production of ethanol from sugarcane is no longer in question; in fact, the burning of sugar-cane residues (bagasse) 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 [ citation needed ] 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; [18] and there are many regions in the country where sugar cane has been cultivated for centuries. [19] 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, where the climate is too cool for sugar cane. In the U.S., agricultural ethanol is generally obtained from grain, chiefly corn. But it can also be obtained from cellulose, a more energy balanced bioethanol.

Clean production bioethanol

Clean production bioethanol [20] is a biofuel obtained by maximizing non-greenhouse gas emitting (renewable) resources:

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

Related Research Articles

<span class="mw-page-title-main">Biofuel</span> Type of biological fuel

Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricultural, domestic or industrial biowaste. Biofuels are mostly used for transportation, but can also be used for heating and electricity. Biofuels are regarded as a renewable energy source. The use of biofuel has been subject to criticism regarding the "food vs fuel" debate, varied assessments of their sustainability, and possible deforestation and biodiversity loss as a result of biofuel production.

<span class="mw-page-title-main">Ethanol fuel</span> Type of biofuel

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.

<i>Panicum virgatum</i> Species of plant

Panicum virgatum, commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico. Switchgrass is one of the dominant species of the central North American tallgrass prairie and can be found in remnant prairies, in native grass pastures, and naturalized along roadsides. It is used primarily for soil conservation, forage production, game cover, as an ornamental grass, in phytoremediation projects, fiber, electricity, heat production, for biosequestration of atmospheric carbon dioxide, and more recently as a biomass crop for ethanol and butanol.

Cellulosic ethanol is ethanol produced from cellulose 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 biofuel. The carbon dioxide that plants absorb as they grow offsets some of the carbon dioxide emitted when ethanol made from them is burned, so cellulosic ethanol fuel has the potential to have a lower carbon footprint than fossil fuels.

<span class="mw-page-title-main">Ethanol fuel in Brazil</span>

Brazil is the world's second largest producer of ethanol fuel. Brazil and the United States have led the industrial production of ethanol fuel for several years, together accounting for 85 percent of the world's production in 2017. Brazil produced 26.72 billion liters, representing 26.1 percent of the world's total ethanol used as fuel in 2017.

<span class="mw-page-title-main">Energy crop</span> Crops grown solely for energy production by combustion

Energy crops are low-cost and low-maintenance crops grown solely for renewable bioenergy production. The crops are processed into solid, liquid or gaseous fuels, such as pellets, bioethanol or biogas. The fuels are burned to generate electrical power or heat.

The United States produces mainly biodiesel and ethanol fuel, which uses corn as the main feedstock. The US is the world's largest producer of ethanol, having produced nearly 16 billion gallons in 2017 alone. The United States, together with Brazil accounted for 85 percent of all ethanol production, with total world production of 27.05 billion gallons. Biodiesel is commercially available in most oilseed-producing states. As of 2005, it was somewhat more expensive than fossil diesel, though it is still commonly produced in relatively small quantities.

<span class="mw-page-title-main">Butanol fuel</span> Fuel for internal combustion engines

Butanol may be used as a fuel in an internal combustion engine. It is more similar to gasoline than it is to ethanol. A C4-hydrocarbon, butanol is a drop-in fuel and thus works in vehicles designed for use with gasoline without modification. Both n-butanol and isobutanol have been studied as possible fuels. Both can be produced from biomass (as "biobutanol" ) as well as from fossil fuels (as "petrobutanol"). The chemical properties depend on the isomer (n-butanol or isobutanol), not on the production method.

Renewable Fuels are fuels produced from renewable resources. Examples include: biofuels, Hydrogen fuel, and fully synthetic fuel produced from ambient carbon dioxide and water. This is in contrast to non-renewable fuels such as natural gas, LPG (propane), petroleum and other fossil fuels and nuclear energy. Renewable fuels can include fuels that are synthesized from renewable energy sources, such as wind and solar. Renewable fuels have gained in popularity due to their sustainability, low contributions to the carbon cycle, and in some cases lower amounts of greenhouse gases. The geo-political ramifications of these fuels are also of interest, particularly to industrialized economies which desire independence from Middle Eastern oil.

Biofuel is fuel that is produced from organic matter (biomass), including plant materials and animal waste. It is considered a renewable source of energy that can assist in reducing carbon emissions. The two main types of biofuel currently being produced in Australia are biodiesel and bioethanol, used as replacements for diesel and petrol (gasoline) respectively. As of 2017 Australia is a relatively small producer of biofuels, accounting for 0.2% of world bioethanol production and 0.1% of world biodiesel production.

<span class="mw-page-title-main">Corn ethanol</span> Ethanol produced from corn biomass

Corn ethanol is ethanol produced from corn biomass and is the main source of ethanol fuel in the United States, mandated to be blended with gasoline in the Renewable Fuel Standard. Corn ethanol is produced by ethanol fermentation and distillation. It is debatable whether the production and use of corn ethanol results in lower greenhouse gas emissions than gasoline. Approximately 45% of U.S. corn croplands are used for ethanol production.

Treethanol is an ethanol fuel made from trees.

<span class="mw-page-title-main">Biofuel in Sweden</span> Use of renewable fuels from living organisms in Sweden

Biofuels are renewable fuels that are produced by living organisms (biomass). Biofuels can be solid, gaseous or liquid, which comes in two forms: ethanol and biodiesel and often replace fossil fuels. Many countries now use biofuels as energy sources, including Sweden. Sweden has one of the highest usages of biofuel in all of Europe, at 32%, primarily due to the widespread commitment to E85, bioheating and bioelectricity.

Second-generation biofuels, also known as advanced biofuels, are fuels that can be manufactured from various types of non-food biomass. Biomass in this context means plant materials and animal waste used especially as a source of fuel.

Biogasoline is a type of gasoline produced from biomass such as algae. Like traditionally produced gasoline, it is made up of hydrocarbons with 6 (hexane) to 12 (dodecane) carbon atoms per molecule and can be used in internal combustion engines. However, unlike traditional gasoline/petroleum based fuels, which are mainly composed from oil, biogasolines are made from plants such as beets and sugarcane or cellulosic biomass- substances normally referred to as plant waste.

<span class="mw-page-title-main">Food vs. fuel</span> Debate concerning diversion of food supply for biofuels production

Food versus fuel is the dilemma regarding the risk of diverting farmland or crops for biofuels production to the detriment of the food supply. The biofuel and food price debate involves wide-ranging views and is a long-standing, controversial one in the literature. There is disagreement about the significance of the issue, what is causing it, and what can or should be done to remedy the situation. This complexity and uncertainty are due to the large number of impacts and feedback loops that can positively or negatively affect the price system. Moreover, the relative strengths of these positive and negative impacts vary in the short and long terms, and involve delayed effects. The academic side of the debate is also blurred by the use of different economic models and competing forms of statistical analysis.

<span class="mw-page-title-main">Sustainable biofuel</span> Non-fossil-based sustainable production

Sustainable biofuel is biofuel produced in a sustainable manner. It is not based on petroleum or other fossil fuels. It includes not using plants that are used for food stuff to produce the fuel thus disrupting the world's food supply.

Issues relating to biofuel are social, economic, environmental and technical problems that may arise from biofuel production and use. Social and economic issues include the "food vs fuel" debate and the need to develop responsible policies and economic instruments to ensure sustainable biofuel production. Farming for biofuels feedstock can be detrimental to the environment if not done sustainably. Environmental concerns include deforestation, biodiversity loss and soil erosion as a result of land clearing for biofuels agriculture. While biofuels can contribute to reduction in global carbon emissions, indirect land use change for biofuel production can have the inverse effect. Technical issues include possible modifications necessary to run the engine on biofuel, as well as energy balance and efficiency.

<span class="mw-page-title-main">Biofuels by region</span> Use of biofuel as energy source across the world

The use of biofuels varies by region. The world leaders in biofuel development and use are Brazil, United States, France, Sweden and Germany.

<span class="mw-page-title-main">Ethanol fuel by country</span>

The world's top ethanol fuel producers in 2011 were the United States with 13.9 billion U.S. liquid gallons (bg) and Brazil with 5.6 bg, accounting together for 87.1% of world production of 22.36 billion US gallons. Strong incentives, coupled with other industry development initiatives, are giving rise to fledgling ethanol industries in countries such as Germany, Spain, France, Sweden, India, China, Thailand, Canada, Colombia, Australia, and some Central American countries.

References

  1. 1 2 Green Dreams J.K. Bourne JR, R. Clark National Geographic Magazine October 2007 p. 41 Article
  2. ↑ 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.
  3. ↑ Estimating the Net Energy Balance of Corn Ethanol Hosein Shapouri, James A. Duffield, and Michael S. Graboski Agricultural Economics Report No. (AER721) 24 pp, July 1995 http://www.ers.usda.gov/media/926108/aer721.pdf Archived 2015-09-24 at the Wayback Machine
  4. ↑ UNL study: Ethanol energy efficiency growing - 29. September 2008
  5. ↑ Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower David Pimentel and Tad W. Patzek Natural Resources Research, Vol. 14, No. 1, March 2005 doi : 10.1007/s11053-005-4679-8 "Archived copy" (PDF). Archived from the original (PDF) on August 9, 2007. Retrieved February 17, 2007.{{cite web}}: CS1 maint: archived copy as title (link)
  6. ↑ Ethanol Can Contribute to Energy and Environmental Goals Alexander E. Farrell, Richard J. Plevin, Brian T. Turner, Andrew D. Jones, Michael O’Hare, Daniel M. Kammen 506 27 January 2006 vol 311 Science http://rael.berkeley.edu/ebamm/FarrellEthanolScience012706.pdf
  7. ↑ http://www.ddgs.umn.edu/more.htm Archived 2007-08-06 at the Wayback Machine University of Minnesota
  8. ↑ "Corn-Based Ethanol Does Indeed Achieve Energy Benefits" (PDF). Archived from the original (PDF) on 2013-12-28. Retrieved 2008-01-05.
  9. ↑ "The 2001 Net Energy Balance of Corn-Ethanol". Archived from the original on 2008-09-13. Retrieved 2008-01-05.
  10. ↑ "The Energy Balance of Corn Ethanol: An Update" (PDF). Archived from the original (PDF) on 2007-05-15. Retrieved 2012-01-19.
  11. ↑ Review of Corn Based Ethanol Energy Use and Greenhouse Gas Emissions [ permanent dead link ]
  12. ↑ http://news.bbc.co.uk/2/hi/science/nature/5353118.stm Biofuels look to the next generation
  13. ↑ Hill, Jason; Nelson, Erik; Tilman, David; Polasky, Stephen; Tiffany, Douglas (July 25, 2006). "Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels". Proceedings of the National Academy of Sciences. 103 (30): 11206–10. Bibcode:2006PNAS..10311206H. doi: 10.1073/pnas.0604600103 . PMC   1544066 . PMID   16837571.
  14. ↑ Grass biofuels 'cut CO2 by 94%' Reported on bbc.co.uk http://news.bbc.co.uk/2/hi/science/nature/7175397.stm
  15. ↑ M. R. Schmer, K. P. Vogel, R. B. Mitchell, and R. K. Perrin Net energy of cellulosic ethanol from switchgrass PNAS published January 7, 2008, doi : 10.1073/pnas.0704767105
  16. ↑ DoE: Biomass Program: Net Energy Balance for Bioethanol Production and Use Quote: "...The most official study of the issue, which also reviews other studies, concludes that the "net energy balance" of making fuel ethanol from corn grain is 1.34...For cellulosic bioethanol—the focus of the Biomass Program—that study projects an energy balance of 2.62...A Biomass Program life-cycle analysis of producing ethanol from stover, now underway, is expected to show a very impressive net energy ratio of more than 5..."
  17. ↑ Net Energy From the Extraction of Oil and Gas in the United States Cutler J. Cleveland http://www.bu.edu/cees/people/faculty/cutler/articles/Net_%20Energy_US_Oil_gas.pdf Archived 2006-09-11 at the Wayback Machine (pdf)
  18. ↑ Em direção à sustentabilidade da produção de etanol de cana de açúcar no Brasil Délcio Rodrigues e Lúcia Ortiz http://www.vitaecivilis.org.br/anexos/etanol_sustentabilidade.pdf Archived 2010-11-02 at the Wayback Machine (pdf)
  19. ↑ Rex A. Hudson, ed. Brazil: A Country Study. Washington: GPO for the Library of Congress, 1997. http://countrystudies.us/brazil/57.htm
  20. ↑ INEOS Bio: Bioethanol: Sustainability Quote: "An independent life-cycle assessment 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
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