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What is Bioethanol Fuel and Its Efficiency

Updated on March 21, 2011


Bioethanol is ethanol produced by a process of fermentation of biomass, ie agricultural products rich in sugar (carbohydrates) such as cereals, sugar crops, the starch and pomace.


For energy bioethanol can be used as a component for gasoline or for the preparation ETBE (ethyl ethylbutyl), a derivative of high octane. Can be used in gasoline in proportions of up to 20% without changing the engine, motor or pure in Flex.


Also you can use bioethanol as a fuel in biocamini, exploiting the power of heat to warm the room. The experimentation on this issue, made by "DOMOSTYL" (which holds the European patent), led to the development of a bio alcohol fireplace 13,000 BTU, or + 16 ° per hour in 70 m2.


The process of bioethanol production generates, depending on the feedstock used, other products with economic value, for use as appropriate to the animal feed, co-generation, etc..


Bioethanol from sugar cane

In Brazil, the yield of ethanol from sugar cane was nearly 6 000 liters per hectare, compared to 2 000 liters in 1975. Ethanol production in Brazil accounts for about 20% of the fuel economy of internal transport.

Typically, the EROEI of ethanol from grain is around the value 1 , the hero made in Brazil with sugar cane and is likely to exceed a value of Brazilian sources claim a 7-8 lead without rigorous proofs. This means that Brazil will produce 6,000 gallons of ethanol consumes 750-860 liters per production cycle, according to Brazilian sources optimistic (do not count administrative expenses).

Bioethanol from the trunk of the plant

Another method that allows the production of bioethanol is to get the first of glucose and produce ethanol by fermentation using. The trunk of the tree, usually spruce, should be properly pre-processed to obtain shredded wood, which is then subjected to cooking and therefore is the extraction of glucose. Once you submit the extract from the hexose substrate for fermentation by Saccharomyces cerevisiae, or yeast organisms which operate in anaerobic conditions and giving them as a final product of the glycolytic pathway in which pyruvate is first decarboxylated to acetaldehyde and after obtaining a hydrogenation, in fact, ethanol. The ethanol produced, however, has a maximum concentration of 25-30% because the yeast have a low ability to withstand high concentrations of alcohol. For this reason it is subjected to azeotropic distillation to obtain a 94-95% ethanol.

Bioethanol from cellulose

Large amounts of cellulose are hydrolysed and through the use of fungi or bacteria convert cellulose to glucose and other sugars, then ferment by yeast or other microbes. Innovative research is aimed at genetically modifying the bacteria, yeasts such as Saccharomyces cerevisiae modified to produce twice as much ethanol. Another avenue of research is to combine the characteristics of break down cellulose into glucose with that of turning sugar into ethanol by a single organization.

Bio-ethanol from cellulose is much more expensive than that obtained from sugar cane and only major scientific advances can make it convenient. Note that the cost is not due to raw material (cellulose), but its transformation into bioethanol. The current industrial processes are the cost of cellulose ethanol three times that obtained from sugar cane.

Efficiency of Bioethanol

For general aspects of biofuel production, energy efficiency, consumption of soil and agricultural resources and so on., See the main entry.

Bioethanol has a calorific value lower than that of gasoline and is an energy carrier that has a thermodynamic efficiency of 30% less than normal fuel. The number of pure ethanol is 113 octane, it is used to raise the octane number of gasoline distillation. This partly compensates for the low calorific value.

Bio-ethanol from grain has, on average, according to some studies an EROEI of about 1 that would be burned to produce a quantity (energy) of fossil fuel that is equal to the amount (energy) of ethanol produced. Therefore, a car powered by ethanol and CO2 pollution would like a car powered by fossil fuel switching. Other studies have found a better EROEI.

Bio-ethanol from cellulose has now cost three times that of cane sugar. The latter is produced only in a limited area of the planet (Brazil) and small amount compared to the global needs.

Nevertheless, the second generation systems (now in full deployment) allow you to use scraps of agricultural products with greater efficiency. This means that in future will not be necessary to cultivate one hectare of cereals for bioethanol production, but just use what remains of the plant as a source of glucose. This obviously entails the elimination of the cost of disposal of waste products (very important in economic and ecological).

Recent studies  point out that although the use of ethanol reduces the concentration of carcinogens such as benzene and butadiene, while rising levels of formaldehyde and acetaldehyde. According to these studies, the overall risk is similar but extensive use may also increase ozone levels in some areas of the planet.

Production Incentives


In the United States Energy Policy Act of 2005 provides strong federal subsidies to farmers to increase production of ethanol from 4 billion gallons in 2006 to 7.5 billion in 2012.


Brazil plans to double ethanol production by the end of 2010 making it one of the biggest exporters being the figure of 5 billion liters is sufficient to supply about 5 million cars.


Sweden, thanks to a program that also includes extensive use of bioethanol for transport, aiming to become the first country in the world independent of oil by 2020


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