Fields of Study
Biology; microbiology; plant biology; chemistry; organic chemistry; biochemistry; agriculture; biotechnology; bioprocess engineering; chemical engineering.
Summary
The study of biofuels and synthetic fuels is an interdisciplinary science that focuses on development of clean, renewable fuels that can be used as alternatives to fossil fuels. Biofuels include ethanol, biodiesel, methane, biogas, and hydrogen; synthetic fuels include syngas and synfuel. These fuels can be used as gasoline and diesel substitutes for transportation, as fuels for electric generators to produce electricity, and as fuels to heat houses (their traditional use). Both governmental agencies and private companies have invested heavily in research in this area of applied science.
Key Terms and Concepts
biodiesel: Biofuel with the chemical structure of fatty acid alkyl esters.
biogas: Biofuel that contains a mixture of methane (50-75 percent), carbon dioxide, hydrogen, and carbon monoxide.
biomass: Mass of organisms that can be used as an energy source; plants and algae convert the energy of the sun and carbon dioxide into energy that is stored in their biomass.
ethanol: Colorless liquid with the chemical formula C2 H5 OH that is used as a biofuel; also known as ethyl alcohol, grain alcohol, or just alcohol.
Fischer-Tropsch process: Process that indirectly converts coal, natural gas, or biomass through syngas into synthetic oil or synfuel (liquid hydrocarbons).
fuel: Any substance that is burned to provide heat or energy.
gasification: Conversion of coal, petroleum, or biomass into syngas.
methane: Colorless, odorless, nontoxic gas, with the molecular formula CH4 , that is the main chemical component of natural gas (70-90 percent) and is used as a biofuel.
molecular hydrogen: Also known by its chemical symbol H2 , a flammable, colorless, odorless gas; hydrogen produced by microorganisms is used as a biofuel and is called a biohydrogen.
synfuel: A synthetic liquid fuel (synthetic oil) obtained via the Fischer-Tropsch process or methanol-to-gasoline conversion.
synthesis gas: Synthetic fuel that is a mixture of carbon monoxide and H2 ; also known as syngas.
Definition and Basic Principles
The science of biofuels and synthetic fuels deals with the development of renewable energy sources, alternatives to nonrenewable fossil fuels such as petroleum. Biofuels are fuels generated from organisms or by organisms. Living organisms can be used to generate a number of biofuels, including ethanol (bioethanol), biodiesel, biomass, butanol, biohydrogen, methane, and biogas. Synthetic fuels (synfuel and syngas) are a class of fuels derived from coal or biomass. Synthetic fuels are produced by a combination of chemical and physical means that convert carbon from coal or biomass into liquid or gaseous fuels.
Around the world, concerns about climate change and possible global warming due to the emission of greenhouse gases from human use of fossil fuels, as well as concerns over energy security, have ignited interest in biofuels and synthetic fuels. A large-scale biofuel and synthetic fuel industry has developed in many countries, including the United States. A number of companies in the United States have conducted research and development projects on synthetic fuels with the intent to begin commercial production of synthetic fuels. Although biofuels and synthetic fuels still require long-term scientific, economic, and political investments, investment in these alternatives to fossil fuels is expected to mitigate global warming, to help protect the global climate, and to reduce U.S. reliance on foreign oil.
Background and History
People have been using biofuels such as wood or dried manure to heat their houses for thousands of years. The use of biogas was mentioned in Chinese literature more than 2,000 years ago. The first biogas plant was built in a leper colony in Bombay, India, in the middle of the nineteenth century. In Europe, the first apparatus for biogas production was built in Exeter, England, in 1895. Biogas from this digester was used to fuel street lamps. Rudolf Diesel, the inventor of the diesel engine, used biofuel (peanut oil) for his engine during the World Exhibition in Paris in 1900. The version of the Model T Ford built by Henry Ford in 1908 ran on pure ethanol. In the 1920’s, 25 percent of the fuels used for automobiles in the United States were biofuels rather than petroleum-based fuels. In the 1940’s, biofuels were replaced by inexpensive petroleum-based fuels.
Gasification of wood and coal for production of syngas has been done since the nineteenth century. Syngas was used mainly for lighting purposes. During World War II, because of shortages of petroleum, internal combustion engines were modified to run on syngas and automobiles in the United States and the United Kingdom were powered by syngas. The United Kingdom continued to use syngas until the discovery in the 1960’s of oil and natural gas in the North Sea.
The process of converting coal into synthetic liquid fuel, known as the Fischer-Tropsch process, was developed in Germany at the Kaiser Wilhelm Institute by Franz Fischer and Hans Tropsch in 1923. This process was used by Nazi Germany during World War II to produce synthetic fuels for aviation.
During the 1970’s oil embargo, research on biofuels and synthetic fuels resumed in the United States and Europe. However, as petroleum prices fell in the 1980’s, interest in alternative fuels diminished. In the twenty-first century, concerns about global warming and increasing oil prices reignited interest in biofuels and synthetic fuels.
How it Works
Biofuels and synthetic fuels are energy sources. People have been using firewood to heat houses since prehistorical time. During the Industrial Revolution, firewood was used in steam engines. In a steam engine, heat from burning wood is used to boil water; the steam produced pushes pistons, which turn the wheels of the machinery.
Biofuels and synthetic fuels such as ethanol, biodiesel, butanol, biohydrogen, and synthetic oil can be used in internal combustion engines, in which the combustion of fuel expands gases that move pistons or turbine blades. Other biofuels such as methane, biogas, or syngas are used in electric generators. Burning of these fuels in electric generators rotates a coil of wire in a magnetic field, which induces electric current (electricity) in the wire.
Hydrogen is used in fuel cells. Fuel cells generate electricity through a chemical reaction between molecular hydrogen (H2 ) and oxygen (O2 ). Ethanol, the most common biofuel, is produced by yeast fermentation of sugars derived from sugarcane, corn starch, or grain. Ethanol is separated from its fermentation broth by distillation. In the United States, most ethanol is produced from corn starch. Biodiesel, another commonly used biofuel, is made mainly by transesterification of plant vegetative oils such as soybean, canola, or rapeseed oil. Biodiesel may also be produced from waste cooking oils, restaurant grease, soap stocks, animal fats, and even from algae. Methane and biogas are produced by metabolism of microorganisms. Methane is produced by microorganisms called Archaea and is an integral part of their metabolism. Biogas produces by a mixture of bacteria and archaea.
Industrial production of biofuels is achieved mainly in bioreactors or fermenters of some hundreds gallons in volume. Bioreactors or fermenters are closed systems that are made of an array of tanks or tubes in which biofuel-producing microorganisms are cultivated and monitored under controlled conditions.
Syngas is produced by the process of gasification in gasifiers, which burn wood, coal, or charcoal. Syngas can be used in modified internal combustion engines. Synfuel can be generated from syngas through Fischer-Tropsch conversion or through methanol to gasoline conversion process.
Applications and Products
Transportation. Biofuels are mainly used in transportation as gasoline and diesel substitutes. As of the early twenty-first century, two biofuels—ethanol and biodiesel—were being used in vehicles. In 2005, the
U.S. Congress passed an energy bill that required that ethanol sold in the United States for transportation be mixed with gasoline. By 2010, almost every fuel station in the United States was selling gasoline with a 10 percent ethanol content. The U.S. ethanol industry has lobbied the federal government to raise the ethanol content in gasoline from 10 to 15 percent. Most cars in Brazil can use an 85 percent/15 percent ethanol-gasoline mix (E85 blend). These cars must have a modified engine known as a flex engine. In the United States, only a small fraction of all cars have a flex engine.
Biodiesel performs similarly to diesel and is used in unmodified diesel engines of trucks, tractors, and other vehicles and is better for the environment. Biodiesel is often blended with petroleum diesel in ratios of 2, 5, or 20 percent. The most common blend is B20, or 20 percent biodiesel to 80 percent diesel fuel. Biodiesel can be used as a pure fuel (100 percent or B100), but pure fuel is a solvent that degrades the rubber hoses and gaskets of engines and cannot be used in winter because it thickens in cold temperatures. The energy content of biodiesel is less than that of diesel. In general, biodiesel is not used as widely as ethanol, and its users are mainly governmental and state bodies such as the U.S. Postal Service; the U.S. Departments of Defense, Energy, and Agriculture; national parks; school districts; transit authorities; public utilities; and waste-management facilities. Several companies across the United States (such as recycling companies) use biodiesel because of tax incentives.
Hydrogen power ran the rockets of the National Aeronautics and Space Administration for many years. A growing number of automobile manufactures around the world are making prototype hydrogen-powered vehicles. These vehicles emit only water, no greenhouse gases, from their tailpipes. These automobiles are powered by electricity generated in the fuel cell through a chemical reaction between H2 and O2 . Hydrogen vehicles offer quiet operation, rapid acceleration, and low maintenance costs because of fewer moving parts. During peak time, when electricity is expensive, fuel-cell hydrogen automobiles could provide power for homes and offices. Hydrogen for these applications is obtained mainly from natural gas (methane and propane), through steam reforming, or by water electrolysis. As of 2010, hydrogen was used only in experimental applications. Many problems need to be overcome before hydrogen becomes widely used and readily available. The slow acceptance of biohydrogen is partly caused by the difficulty in producing it on a cost-effective basis. For hydrogen power to become a reality, a great deal of research and investment must take place.
Fascinating Facts about Biofuels and Synthetic Fuels
Scientists have discovered that Gliocladium roseum , a tree fungus, is able to convert cellulose directly into biodiesel, thus making transesterification unnecessary. The fungus eats the tree and, interestingly, keeps other fungi away from the tree by producing an antibiotic. Scientists are studying enzymes that will help this fungus eat cellulose.
Termites can produce two liters of biofuel, molecular hydrogen, or H2 , by fermenting just one sheet of paper with microbes that live in their guts. Study of the biochemical pathways involved in H2 production in termite guts may lead to application of this process industrially.
In 2009, Continental Airlines successfully powered a Boeing 737-800 using a biodiesel fuel mixture partly produced from algae.
Firewood can power an automobile, but its engine must be modified slightly and a trailer with a syngas generator (gasifier) must be attached to the automobile.
An automobile that runs on diesel fuel can easily be modified to run on used cooking oil, which can be obtained for little or no charge from local restaurants.
By attaching a water electrolyzer, an automobile can be modified to run partly on water. Electricity from the car battery splits water in the electrolyzer into hydrogen and oxygen. The hydrogen can be burned in the internal combustion engine and power the automobile.
Modifying an automobile to run partly on methane is simple and definitely saves gasoline.
Methane was used as a fuel for vehicles for a number of years. Several Volvo automobile models with Bi-Fuel engines were made to run on compressed methane with gasoline as a backup. Biogas can also be used, like methane, to power motor vehicles.
Electricity generation. Biogas and methane are mainly used to generate electricity in electric generators. In the 1985 film Mad Max Beyond Thunderdome , starring Mel Gibson, a futuristic city ran on methane generated by pig manure. While the use of methane has not reached this stage, methane is a very good alternative fuel that has a number of advantages over biofuels produced by microorganisms. First, it is easy to make and can be generated locally, eliminating the need for an extensive distribution channel. Second, the use of methane as a fuel is a very attractive way to reduce wastes such as manure, wastewater, or municipal and industrial wastes. In farms, manure is fed into digesters (bioreactors), where microorganisms metabolize it into methane. There are several landfill gas facilities in the United States that generate electricity using methane. San Francisco has extended its recycling program to include conversion of dog waste into methane to produce electricity and to heat homes. With a dog population of 120,000, this initiative promises to generate a significant amount of fuel and reduce waste at the same time.
Heat generation. Some examples of biomass being used as an alternative energy source include the burning of wood or agricultural residues to heat homes. This is a very inefficient use of energy, because typically only 5 to 15 percent of the biomass energy is actually used. Burning biomass also produces harmful indoor air pollutants such as carbon monoxide. On the positive side, biomass is an inexpensive resource whose costs are only the labor to collect it. Biomass supplies more than 15 percent of the energy consumed worldwide. Biomass is the number-one source of energy in developing countries; in some countries, it provides more than 90 percent of the energy used.
In many countries, millions of small farmers maintain a simple digester for biogas production to generate heat energy. More than 5 million household digesters are being used in China, mainly for cooking and lighting, and India has more than 1 million biogas plants of various capacities.
Impact on Industry
In 2009, the annual revenue of the global biofuels industry was $46.5 billion, with revenue in the United States alone reaching $20 billion. The United States is leading the world in research on biofuels and synthetic fuels. Significant biofuels and synthetic fuels research has also been taking place in many European countries, Russia, Japan, Israel, Canada, Australia, and China.
Government and university research. Many governmental agencies such as the U.S. Department of Energy (DOE), the National Science Foundation (NSF), and the U.S. Department of Agriculture provide funding for research in biofuels and synthetic fuels. The DOE has several national laboratories (such as the National Renewable Energy Laboratory in Golden, Colorado) where cutting-edge research on biofuels and synthetic fuels is performed. In addition, three DOE research centers are concentrated entirely on biofuels. These centers are the BioEnergy Science Center, led by Oak Ridge National Laboratory; the Great Lakes Bioenergy Research Center, led by the University of Wisconsin, Madison; and the Joint BioEnergy Institute, led by Lawrence Berkeley National Laboratory.
In 2007, DOE established the Advanced Research Projects Agency-Energy (ARPA-E) to fund the development and deployment of transformational energy technologies in the United States. Several projects funded by this agency are related to biofuels, such as the development of advanced or second-generation biofuels. Traditional biofuels such as biomass (wood material) and ethanol and biodiesel from crops are sometimes called first-generation biofuels. Second-generation biofuels such as cellulosic ethanol are produced from agricultural and forestry residues and do not take away from food production. Another second-generation biofuel is biohydrogen.
Biofuels such as butanol are referred to as third-generation biofuels. Butanol (C4 H9 OH) is an alcohol fuel, but compared with ethanol, it has a higher energy content (roughly 80 percent of gasoline energy content). It does not absorb water as ethanol does, is not as corrosive as ethanol is, and is more suitable for distribution through existing gasoline pipelines.
Scientists are trying to create “super-bugs” for superior biofuel yields and studying chemical processes and enzymes to improve existing bioprocesses for biofuels production. They also are working to improve the efficiency of the existing production process and to make it more environmentally friendly. Engineers and scientists are designing and developing new apparatuses (bioreactors or fermenters) for fuel generation and new applications for by-products of fuel production.
Industry and business sectors. The major products of the biofuel industry are ethanol, biodiesel, and biogas; therefore, research in industry has concentrated mainly on these biofuels. Some small businesses in the biofuel industry include startup research and development companies that study feedstocks (such as cellulose) and approaches for production of biofuels at competitive prices. These companies, many of which are funded by investment firms or government agencies, analyze biofuel feedstocks, looking for new feedstocks or modifying existing ones (corn, sugarcane, or rapeseed).
Big corporations such as Poet Energy, ExxonMobil, and BP are spending a significant part of their revenues on biofuel or synthetic fuels research. One area of biofuel research examines using algae to generate biofuels, especially biodiesel. More than fifty research companies worldwide, including GreenFuel Technologies, Solazyme, and Solix Biofuels, are conducting research in this area. Research conducted by the U.S. Department of Energy Aquatic Species Program from the 1970’s to the 1990’s demonstrated that many species of algae produce sufficient quantities of oil to become economical feedstock for biodiesel production. The oil productivity of many algae greatly exceeds the productivity of the best-producing oil crops. Algal oil content can exceed 80 percent per cell dry weight, with oil levels commonly at about 20 to 50 percent. In addition, crop land and potable water are not required to cultivate algae, because algae can grow in wastewater. Although development of biodiesel from algae is a very promising approach, the technology needs further research before it can be implemented commercially.
Careers and Course Work
The alternative fuels industry is growing, and research in the area of biofuels and synthetic fuels is increasing. Growth in these areas is likely to produce many jobs. The basic courses for students interested in a career in biofuels and synthetic fuels are microbiology, plant biology, organic chemistry, biochemistry, agriculture, bioprocess engineering, and chemical engineering. Many educational institutions are offering courses in biofuels and synthetic fuels, although actual degrees or concentrations in these disciplines are still rare. Several community colleges offer associate degrees and certificate programs that prepare students to work in the biofuel and synthetic fuel industry. Some universities offer undergraduate courses in biofuels and synthetic fuels or concentrations in these areas. Almost all these programs are interdisciplinary. Graduates of these programs will have the knowledge and internship experience to enter directly into the biofuel and synthetic fuel workforce. Advanced degrees such as a master’s degree or doctorate are necessary to obtain top positions in academia and industry related to biofuels and synthetic fuels. Some universities such as Colorado State University offer graduate programs in biofuels.
Careers in the fields of biofuels and synthetic fuels can take different paths. Ethanol, biodiesel, or biogas industries are the biggest employers. The available jobs are in sales, consulting, research, engineering, and installation and maintenance. People who are interested in research in biofuels and synthetic fuels can find jobs in governmental laboratories and in universities. In academic settings, fuel professionals may share their time between research and teaching.
Social Context and Future Prospects
The field of biofuels and synthetic fuels is undergoing expansion. Demands for biofuels and synthetic fuels are driven by environmental, social, and economic factors and governmental support for alternative fuels.
The use of biofuels and synthetic fuels reduces the U.S. dependence on foreign oil and helps mitigate the devastating impact of increases in the price of oil, which reached a record $140 per barrel in 2008. The production and use of biofuels and synthetic fuels reduces the need for oil and has helped hold world oil prices 15 percent lower than they would have been otherwise. Many experts believe that biofuels and synthetic fuels will replace oil in the future.
Pollution from oil use affects public health and causes global climate change because of the release of carbon dioxide. Using biofuels and synthetic fuels as an energy source generates fewer pollutants and little or no carbon dioxide.
The biofuel and synthetic fuel industry in the United States was affected by the economic crisis in 2008 and 2009. Several ethanol plants were closed, some plants were forced to work below capacity, and other companies filed for Chapter 11 bankruptcy protection. Such events led to layoffs and hiring freezes. Nevertheless, overall, the industry was growing and saw a return to profitability in the second half of 2009. Worldwide production of ethanol and biodiesel is expected to grow to $113 billion by 2019; this is more than 60 percent growth of annual earnings. One segment of the biofuel and synthetic fuel industry, the biogas industry, was not affected by recession at all. More than 8,900 new biogas plants were built worldwide in 2009. According to market analysts, the biogas industry has reached a turning point and may grow at a rate of 24 percent from 2010 to 2016. Research and development efforts in biofuels and synthetic fuels actually increased during the economic crisis. In general, the future of biofuels and synthetic fuels is bright and optimistic.
—Sergei A. Markov, PhD
Further Reading
Bart, Jan C. J., and Natale Palmeri. Biodiesel Science and Technology: From Soil to Oil . Cambridge, England: Woodhead, 2010. A comprehensive book on biodiesel fuels.
Bourne, Joel K. “Green Dreams.” National Geographic 212, no. 4 (October, 2007): 38-59. An interesting discussion about ethanol and biodiesel fuels and their future.
Glazer, Alexander N., and Hiroshi Nikaido. Microbial Biotechnology: Fundamentals of Applied Microbiology . New York: Cambridge University Press, 2007. Provides an in-depth analysis of ethanol and biomass for fuel applications.
Mikityuk, Andrey. “Mr. Ethanol Fights Back.” Forbes , November 24, 2008, 52-57. Excellent discussion about the problems and the hopes of the ethanol industry. Examines how the ethanol industry fought the economic crisis in 2008 and returned to profitability in 2009.
Probstein, Ronald F., and Edwin R. Hicks. Synthetic Fuels . Mineola, N.Y.: Dover Publications, 2006. A comprehensive work on synthetic fuels. Contains references and sources for further information.
Service, Robert F. “The Hydrogen Backlash.” Science 305, no. 5686 (August 13, 2004): 958-961. Discusses the future of hydrogen power, including its maturity. Written in an easy-to-understand manner.
Wall, Judy, ed. Bioenergy . Washington, D.C.: ASM Press, 2008. Provides the information on generation of biofuels by microorganisms and points out future areas for research. Ten chapters focus on ethanol production from cellulosic material.