Where Found (Encyclopedia of Global Resources)
Primary Uses (Encyclopedia of Global Resources)
Biofuels such as ethanol and biodiesel are excellent transportation fuels that are used as substitutes or supplements for gasoline and diesel fuels. Biofuels can also be burned in electrical generators to produce electricity. Two biofuels are used in vehicles: ethanol and biodiesel. Biogas and methane are used mainly to generate electricity. Biomass was used traditionally to heat houses.
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Technical Definition (Encyclopedia of Global Resources)
Biofuels are renewable fuels generated from or by organisms. They can be manufactured from this organic matter and, unlike fossil fuels, do not require millennia to be produced. Since they are renewable, biofuels are considered by many as potential future substitutes for fossil fuels, which are nonrenewable and dwindling. Moreover, pollution from fossil fuels affects public health and has been associated with global climate change, because burning them in engines releases carbon dioxide (CO2) into the atmosphere. Using biofuels as an energy source generates fewer pollutants and little or no carbon dioxide. In addition, the utilization of biofuels reduces U.S. dependence on foreign oil.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
Over millions of years, dead organic matter—both plant and animal organisms—played a crucial role in the formation of fossil fuels such as oil, natural gas, and coal. Since the nineteenth century, humans have increasingly depended on fossil fuels to meet energy needs. As the supply of fossil fuels has diminished, humankind has begun looking for alternative energy sources. Thus, the use of biofuels—including ethanol, biodiesel, methane, biogas, biomass, biohydrogen, and butanol—is increasing.
Ethanol is a colorless liquid with the chemical formula C2H5OH. Another name for ethanol is ethyl alcohol, grain alcohol, or simply alcohol.
Biodiesel is a diesel substitute obtained mainly from vegetable oils, such as soybean oil or restaurant greases. It is produced by the transesterification of oils, a simple chemical reaction with alcohol (ethanol or methanol), catalyzed by acids or bases (such as sodium hydroxide). Transesterification produces alkyl esters of fatty acids that are biodiesel and glycerol (also known as glycerin).
Methane is a colorless, odorless, nontoxic gas with the molecular formula CH4. It is the main chemical component (70 to 90 percent) of natural gas, which accounts for about 20 percent of the U.S. energy supply. Methane was discovered by the Italian scientist Alessandro Volta, who collected it from marsh sediments and showed that it was flammable. He called it...
(The entire section is 531 words.)
History (Encyclopedia of Global Resources)
The concept of biofuels is not new. People have been using biomass such as plant material to heat their houses for thousands of years. The idea of using hydrogen as fuel was expressed by Jules Verne in his novel L’Île mystérieuse (1874-1875; The Mysterious Island, 1875). In 1900, Rudolf Diesel, the inventor of the diesel engine, used peanut oil for his engine during the World Exhibition in Paris, France. Henry Ford’s first (1908) car, the Model T, was made to run on pure ethanol. Later, the popularity of biofuels as a fuel source followed the “oil trouble times.” For example, biofuels were considered during the 1970’s oil embargo. Early in the twenty-first century, concerns about global warming and oil-price increases reignited interest in biofuels. In 2005, the U.S. Congress passed the Energy Policy Act, which included several sections related to biofuels. In particular, this energy bill required more research on biofuels, mixing ethanol with gasoline, and an increase in the production of cellulosic biofuels.
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Obtaining Biofuels (Encyclopedia of Global Resources)
Ethanol is produced mainly by the microbial fermentation of starch crops (such as corn, wheat, and barley) or sugarcane. In the United States, most of the ethanol is produced by the yeast (fungal) fermentation of sugar from cornstarch. Ethanol can be produced from cellulose, the most plentiful biological material on Earth; however, current methods of converting cellulosic material into ethanol are inefficient and require intensive research and development efforts. Ethanol can also be produced by chemical means from petroleum. Therefore, ethanol that is produced by microbial fermentation is commonly referred to as “bioethanol.”
In the United States, biodiesel comes mainly from soybean plants; in Europe, the world’s top producer of biodiesel, it comes from canola oil. Other vegetative oils that have been used in biodiesel production are corn, sunflower, cottonseed, jatropha, palm oil, and rapeseed. Another possible source for biodiesel production is microscopic algae (microalgae), the microorganisms similar to plants.
Methane is produced by microorganisms and is an integral part of their metabolism. Biogas is produced during the anaerobic fermentation of organic matter by a community of microorganisms (bacteria and archaea). For practical use, methane and biogas are generated from wastewater, animal waste, and “gas wells” in landfills. Biomass is produced naturally, in the forest, and agriculturally, from...
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Uses of Biofuels (Encyclopedia of Global Resources)
With increasing energy demands and oil prices, ethanol has become a valuable option as an alternative transportation fuel. The Energy Policy Act of 2005 included a requirement to increase the production of ethanol from 15 to 28 billion liters by 2012. Beginning in 2008, a majority of fuel stations in the United States were selling gasoline with 10 percent ethanol in it. Nearly all cars can use E10, fuel that is 10 percent ethanol. Blending ethanol with gasoline oxygenates the fuel mixture, which burns more completely and produces fewer harmful CO emissions. Another environmental benefit of ethanol is that it degrades in the soil, whereas petroleum-based fuels are more resistant to degradation and have many damaging effects when accidentally discharged into the environment. However, a liter of ethanol has significantly less energy content than a liter of gasoline, so vehicles must be refueled more often. Ethanol is also more expensive than gasoline, although rising prices of gasoline could cancel that disadvantage. In addition, carcinogenic aldehydes, such as formaldehyde, are produced when ethanol is burned in internal combustion engines. Carbon dioxide, a major greenhouse gas, forms as well. Moreover, the widely used fuel mix that is 85 percent ethanol and 15 percent gasoline (the E85 blend) requires specially equipped “flexible fuel” engines. In the United States, only a fraction of all cars are considered “flex fuel”...
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Further Reading (Encyclopedia of Global Resources)
Chisti, Yusuf. “Biodiesel from Microalgae.” Biotechnology Advances 25, no. 3 (2007): 294-306.
Glazer, Alexander N., and Hiroshi Nikaido. Microbial Biotechnology: Fundamentals of Applied Microbiology. New York: W. H. Freeman, 2007.
Service, Robert F. “The Hydrogen Backlash.” Science 305, no. 5686 (August 13, 2004): 958-961.
Wald, Matthew L. “Is Ethanol for the Long Haul?” Scientific American 296, no. 1 (January, 2007): 42-49.
Wright, Richard T. Environmental Science: Towards a Sustainable Future. 9th ed. Englewood Cliffs, N.J.: Prentice Hall, 2004.
AE Biofuels. http://www.alternative-energy-news.info/technology/biofuels/
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Definition (Encyclopedia of Global Warming)
Biofuels are renewable fuels generated from organisms or by organisms. biofuels are considered by many as a future substitute for fossil fuels. For millions of years, living organisms played a crucial role in the formation of fossil fuels such as oil, natural gas, and coal. As fossil fuels are being depleted, humankind is looking for alternative energy sources. Once again, living organisms can be used to generate such fuels, including ethanol, biodiesel, butanol, biohydrogen, and biogas (mostly methane). One of the applications for biofuels is to use them as gasoline and diesel substitutes. At present, two biofuels are used in vehicles globally: ethanol and biodiesel. Biogas is mainly used to generate electricity. These biofuels are made from plant biomass, including corn, soybean, sugarcane, rapeseed, and other plant material. Solar energy is converted and stored in plant cells in the form of carbohydrates or lipids, and this energy can be transferred into biofuel energy.
Ethanol (C2H5OH), or grain alcohol, the most common biofuel, is produced by yeast fermentation of sugars derived from sugarcane, corn starch, and grain. In the United States, most of ethanol is produced from corn starch. Biodiesel, another commonly used biofuel, is made mainly by transesterification of plant oils, such as soybean, canola, or rapeseed oil. Its chemical structure is that of the fatty acids alkyl esters. biodiesel may also be produced from waste...
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Significance for Climate Change (Encyclopedia of Global Warming)
Use of fossil fuels releases carbon dioxide (CO2), which contributes to global warming. Biofuel utilization can produce considerably less CO2 compared to fossil fuel utilization. In general, burning biofuels releases only that CO2 that was captured by plants during photosynthesis. They can be considered “CO2 neutral,” in that the CO2 released by burning can be reassimilated by plants. However, significant amounts of CO2 are also generated during biofuel production. Estimated CO2 emission during production of biofuels greatly depends on the method of their manufacture.
Production of biofuels from crops such as corn under the current fossil-fuel-based agricultural system would significantly increase greenhouse emissions. Emissions result from growing feedstock, applying fertilizers, transporting the feedstock to factories, processing the feedstock into biofuels, and transporting biofuels to their point of use. Manufacturing biofuels from corn starch and plant vegetable oil requires burning considerable amounts of natural gas, diesel, or coal to provide energy.
In contrast, net emissions of CO2 during biofuel production from lignocellulose can be nearly zero. Lignocellulose is a combination of lignin, cellulose, and hemicellulose that strengthens plant cell walls. Cellulose and hemicellulose are made from sugars that can be converted into biofuels. Electricity from burning the lignin could provide...
(The entire section is 488 words.)
Further Reading (Encyclopedia of Global Warming)
Chisti, Yusuf. “Biodiesel from Microalgae.” Biotechnology Advances 25 (2007): 294-306. Review of the current state of technology for generating biodiesel from microalgae.
Glazer, Alexander N., and Hiroshi Nikaido. Microbial Biotechnology: Fundamentals of Applied Microbiology. New York: Cambridge University Press, 2007. Analysis of the pros, cons, and pitfalls of generating and burning ethanol for fuel.
Wald, Matthew L. “Is Ethanol for the Long Haul?” Scientific American, January, 2007, 42-49. Excellent discussion about the future of ethanol fuel.
(The entire section is 72 words.)