Ethanol Production: A Past Paper PDF

The airport terminal in Sioux Falls, S.D.,could be anywhere, until you reach the bag-gage claim area. Between the carousels is a green and white Indy-style race car, covered with decals that indicate it runs on ethanol. Approach the rent-a- car booths, and you will see a sign taped to the counter...

The airport terminal in Sioux Falls, S.D.,could be anywhere, until you reach the bag-gage claim area. Between the carousels is a green and white Indy-style race car, covered with decals that indicate it runs on ethanol. Approach the rent-a- car booths, and you will see a sign taped to the countertop re-minding customers not to pump E85, the ultra-ethanol blend sold locally, into the rental cars because they are not designed for it and it will ruin their engines. This is ethanol country, the center of the national push to turn carbohydrates into hydrocarbons. The U.S. has gone on an ethanol binge,anticipating a fuel transition unrivaled since electric utilities set out 40 years ago to build hundreds of nuclear power plants. In August 2005 Congress passed a major energy bill calling for production of 7.5 billion gallons of ethanol a year from corn kernels, and it is energy-intensive to produce. Some by 2012, up from about four billion gallons at the time, to studies indicate that refining a gallon of ethanol takes more help displace imported fuel. Industry analysts say the nation energy than it provides when combusted. Even the positive will be burning that much ethanol long before the deadline, studies demonstrate only a slight net energy gain. Other re- thanks to government tax rules and subsidies — and especial- search shows that the ethanol-from-corn cycle reduces green- ly if oil prices stay high — because the cost to convert plant house gases marginally or not at all compared with gasoline matter into ethanol is far below the $2.50 a gallon that gaso- from crude. line was fetching last fall. Ethanol will not make economic or environmental sense Indeed, according to the Renewable Fuels Association, until refiners perfect methods to derive the fuel from cellulose, domestic ethanol production was more than five billion gal- not corn. Cellulose is the woody material that forms the stalk lons in 2006. That quantity is small compared with gasoline of a corn plant and the bodies of trees and other plants such and diesel consumption of about 140 billion gallons annually, as grasses, which require less energy to tend and harvest. But Ironically, to make “domestic” corn ethanol, the U.S. will have to increase imports of natural gas. but it is up 50 percent in one year. Andy Karsner, the assistant although scientists understand the biology-based processes secretary of energy for efficiency and renewable energy at the that convert the sugars tied up in cellulose, companies trying DOE , says that because of the market pull exerted by the high to make ethanol from these materials have so far not reached price of oil, developers are scrambling to build ethanol plants. commercial viability. Sugarcane is the ultimate plant source, There is an ethanol boom, he says, “a little like the Pennsyl- far richer than cornstalks and grasses in the sugars that are vania oil rush in the 1850s.” distilled into ethanol, but the U.S. does not have the climate But is the rush worth it? Not the way we generate ethanol or cheap labor to exploit that crop the way Brazil has. now. All the fuel ethanol sold commercially in the U.S. comes Making ethanol production from cellulose practical will require agricultural advances and major improvements in in- Overview/Myth and Reality dustrial processing. Without those steps, ethanol will remain a cumbersome product with little net benefit, and the country Although politicians are aggressively pushing ethanol will remain dependent on foreign oil. from homegrown corn as a substitute for foreign oil, the conversion makes little energy sense. It requires Renewable? Not Really copious amounts of fossil fuels, and even if 100 percent mos t e t h a nol p roduc e d in the U.S. is sold as a kind of of the U.S. corn supply was distilled into ethanol it Hamburger Helper for gasoline. It may constitute up to 10 would supply only a small fraction of the fuel consumed percent of the blend, the most that conventional engines can by the nation’s vehicles. handle without damage. In some locales, primarily the farm Studies show that producing ethanol from corn creates belt, drivers can find the E85 blend— 85 percent ethanol and almost the same amount of greenhouse gases as 15 percent unleaded regular gasoline. This mix requires spe- gasoline production does. Burning ethanol in vehicles cially equipped “flexible fuel” engines designed to tolerate it. offers little if any pollution reduction. Otherwise the ethanol— the same form of alcohol as in dis- Deriving ethanol from cellulose — cornstalks and the tilled liquor— eats away at the seals in the engine and fuel straw of grains and grasses — consumes far less fossil system. Several million vehicles are so equipped (although fuel than ethanol from corn kernels. But companies many owners do not know it), but there are only a few hun- have had trouble coaxing the natural enzymes needed dred places that sell E85, and the fuel supply chain is expand- for conversion to multiply and work inside the large ing slowly. bioreactors required for volume production. More Nevertheless, ethanol from corn is surging in part because promising organisms are being discovered; ethanol’s it has a strong bipartisan constituency of farm-state senators long-term viability depends on their success. and representatives in Washington, D.C. It also has support from people outside agriculture who believe the country  FUEL CONSUMED Diesel FROM WELL TO WHEEL: HOW FUEL IS MADE Many steps are required to convert oil into gasoline and corn into ethanol and to deliver them to the local pump. Natural gas Some stages are energy-intensive, consuming volumes of fossil fuels. Corn farming Oil drilling Feedlot Corn transportation Fertilizer production By-product Oil pipeline dryer Ethanol production Refining Ethanol transportation Gasoline transportation w w w. s c ia m. c o m SCIENTIFIC A MERIC A N 45 ETHANOL FROM KERNELS OR STALKS Hammer mill Slurry tank Jet cooker The initial steps in converting corn or cellulose into ethanol differ significantly. Corn is ground, cooked and CORN PRODUCTION mashed before entering a fermenter. Cellulose is steamed to expose fibers that enzymes then Enzymes convert into sugars in a bioreactor. Companies are still looking for bioreactions that are efficient on a large scale, but one payoff is the lignin that remains behind, which can be burned to CELLULOSE PRODUCTION Steamer Bioreactor cogenerate steam and Steam Lignin electricity. The distillation of either raw material creates stillage, a valuable by-product that can be processed into animal feed. Cogeneration plant should be less dependent on imported oil. Advocates argue densing it. Natural gas is used for heating at various steps. that ethanol is a renewable fuel, because the corn can be Producing a gallon of ethanol, with its 80,000 Btu of energy, grown year after year. The Renewable Fuels Association has currently requires about 36,000 Btu of natural gas. a slick pamphlet that implies that consuming 7.5 billion gal- In the 1990s, when Congress tried to prop up farm-state lons a year means 179 million fewer barrels of foreign oil. economies with laws that encouraged refiners to make more That level would equal about 15 days of imports — a start, if ethanol, natural gas was cheap, averaging around $3 per mil- not a cure-all. lion Btu. Last winter the price hit $14. Furthermore, high But there is less to ethanol than meets the eye. The first demand pushes natural gas prices up for everyone. Although problem is that a standard barrel (42 gallons) of ethanol is ethanol backers say their fuel is part of a sustainable energy worth about 28 gallons of gasoline because it contains only future, using so much natural gas may not be sustainable, 80,000 British thermal units (Btu) of energy, versus about even in the present. American production is falling, and Ca- 119,000 for unleaded regular. If you fill your tank with E85, nadian production is not sufficient to match consumption. you will run dry about 33 percent sooner. Even if a gallon of Ironically, to make “domestic’’ ethanol, the U.S. will have to ethanol were cheaper at the pump, drivers would have to buy increase natural gas imports from outside North America. many more gallons to go the same distance. As an alternative, some ethanol producers are burning The other earworm in the ointment is that the U.S. lacks coal, which fits nobody’s definition of clean and renewable. some of the resources to produce ethanol. The country has Using coal releases so much carbon dioxide that driving a mile corn in abundance, spreading out in all directions from the on that ethanol is worse for climate change than driving a Sioux Falls airport. But manufacturing ethanol requires copi- mile on plain old gasoline. In theory, a distillery could pro- ous amounts of natural gas. Basically, ethanol for fuel is pro- duce heat with electricity purchased from a power company, duced the same way that ethanol for liquor is made. Yeast eats but for many U.S. utilities, that would mean burning more sugar and gives off alcohol and carbon dioxide. The output is coal and natural gas to supply the demand. distilled, vaporizing the alcohol, then capturing and recon- Ethanol requires other forms of energy, too. The obvious  Distiller Enzymes Ethanol capture Fermenter Molecular sieve Masher Stillage Centrifuge Electricity to the grid Drum dryer Animal feed one is diesel fuel for trucks that haul it to market— and it is percent energy yield from sugarcane as harvested in Brazil. sometimes a very long haul, because ethanol is not shipped in Michael Wang, an environmental scientist at Argonne Na- pipelines like gasoline and diesel are. Pipelines are readily tional Laboratory’s Center for Transportation Research, has contaminated with water, which does not mix with gasoline calculated that making a million Btu of ethanol requires or diesel but does bind with ethanol, ruining its fuel value. 740,000 Btu of fossil fuels, when considering all the steps in Diesel fuel also runs the combines that harvest the corn. And the chain— fertilizing fields, harvesting the corn, distilling its the corn is usually fertilized with chemicals made with natu- starch into alcohol, and so on. Ethanol is promoted as a farm ral gas. product, but it is largely a product of fossil fuels. These considerations are key to the calculation of a “net The greenhouse benefit of ethanol is even smaller. Writing energy balance” for ethanol. The figure is the subject of lively in Science in January 2006, Alexander E. Farrell, an assistant debate. David Pimentel, a professor of agriculture at Cornell professor of energy and resources at the University of Califor- University, asserted in 2005 that it takes more energy to make nia, Berkeley, declared that the effect on greenhouse gases was a gallon of ethanol than the fuel produces when burned. Crit- “ambiguous.” After reviewing various studies, Farrell and his ics argued he had assigned too little value to by-products, co-authors concluded that ethanol made with natural gas is some of which can be fed to livestock (displacing the need to marginally better than gasoline production for global warm- grow some corn), and that he had billed ethanol for extrane- ing pollutants, but ethanol made with coal is worse. Burning ous energy costs, including the value of the food eaten by workers at ethanol plants. But the consensus among the ana- THE AUTHOR MATTHEW L. WALD is a reporter at the New York Times, where he lysts is that even if the net energy value of ethanol is positive, has covered energy topics since 1979. He has written about oil the margin is small. That same year a large study by the Amer- refining, electricity production, electric and hybrid automobiles, ican Institute of Biological Sciences concluded that ethanol and air pollution. Wald is currently assigned in Washington, D.C., from corn yielded only about 10 percent more energy than where he also tracks transportation safety and other subjects. was required to produce it. That finding compared with a 370 This feature article is his third for Scientific American. TAKES FUEL TO MAKE FUEL and pollution. He is referring to Archer Daniels Midland, the agricultural products giant, which has for years been a driv- Vastly different amounts of fossil fuel (natural ing force behind ethanol policy. gas, oil and coal) are burned to produce gasoline and ethanol, considering all the steps Life-cycle analysis of fuels does seem to be a new idea to from drilling or the people who set energy policy. For the first time, instead of farming to final assessing the payoff of converting low-value Btu to high-value delivery. The Btu (such as coal to electricity or crude oil to gasoline) simply numbers below are on the basis of price, analysts are starting to regard the en- averages derived ergy losses and pollution releases along the way. from six studies by Whether such assessments will inform policy is another California Institute question, however. For example, a broad-based coalition of of Technology biofuels, wind and solar power advocates has formed an um- researchers. brella group calling itself “25  ’25.” They want 25 percent of the nation’s energy to come from renewable sources by 2025. Dozens of members of Congress are endorsing the JUNGLE ROT from Guam (the fungus group, yet at a news conference last spring in Washington, Trichoderma reesei) helps to break D.C., held to introduce the organization, its leaders could not down cellulose into sugars that can be readily distilled into ethanol. even say whether wind, solar, ethanol or direct combustion of biomass would be the largest source. There was little desire to blemish the concept with arithmetic. Some of the sudden interest in ethanol is actually an unin- tended consequence of a failed policy effort to tinker with the 1.19 recipe for gasoline. In the 1980s some states began requiring 1.0 certain oxygen levels in gasoline, an ill-advised attempt to One Megajoule of Fuel make cars burn cleaner. In response, most refiners added methyl tertiary butyl ether (MTBE) — and not ethanol — to 0.77 gasoline. (Critics said the politicians’ hidden motivation was to help farm states by boosting ethanol use.) Over the ensuing years, inspectors found that whenever gasoline leaked into the dirt, MTBE — a possible carcinogen — readily migrated into local drinking water. In the 2005 Energy Act, Congress eliminated the rule that 0.10 encouraged MTBE, and refiners dropped the stuff because of Gasoline Corn Cellulose potential liability problems. But the refiners needed another Ethanol Ethanol high-octane substitute and feared new initiatives calling for Megajoules of Fossil Energy oxygen levels, so they rushed to ethanol. American oil refiner- to Produce One Megajoule of Fuel ies also happen to be short on capacity, so adding ethanol would stretch the volume of gasoline they produce, forestall- ing the need to build costly new plants. a gallon of gasoline releases about 20 pounds of carbon diox- The Stalk, Not the Ear ide, counting the contributions from the car engine as well as o n e o t h e r fundamental problem plagues the current the refinery. The comparable figure for ethanol is a matter of scheme for ethanol: corn. The crop is in surplus right now, but some dispute, but it varies from slightly better to slightly even that is not nearly enough to quench a significant portion worse, depending on how the ethanol is made. Promoting a of the country’s thirst for fuel. switch to ethanol on the basis of limiting emissions of climate- Pimentel wrote in a letter to Senator John McCain of Ari- changing gases is deceptive. zona in February 2005 that making 3.4 billion gallons of ethanol was consuming about 14 percent of America’s corn Life Cycle or Political Cycle? crop. At that rate, he pointed out, 100 percent of the nation’s u n for t u n at e ly, net energy and pollution considerations corn crop would supply only 7 percent of the fuel consumed may not have played much of a role in the federal govern- by its vehicles. Even if the corn crop grew much bigger some- ment’s 2005 setting of a “renewable fuel standard’’ for 2012 how, U.S. farmers could never grow anywhere near the or in giving ethanol a 51-cent-per-gallon tax break. “Con- amount of corn needed to fuel the nation. And critics say any gress didn’t do a life-cycle analysis; it did an ADM analysis,” acceleration in agriculture should be used to raise crop ex- says one federal official with long-term experience in energy ports or feed the world’s starving people.  A solution would be to derive ethanol from cellulose. Cel- quantities needed to sustain conversion to ethanol inside such lulose forms the stalk of a corn plant, the straw of grains, and a space. the body of other plants not typically thought of as crops, Several companies have made their proprietary processes such as some fast-growing grasses. Much more cellulose ex- work, but it does not appear that any has done so with enough ists than corn kernels; according to the Department of Agri- consistency to persuade lenders. Although they have not been culture and others, massive harvesting of cellulose across the explicit about their technical problems, at a seminar at the nation could generate enough ethanol to replace one third of House of Representatives last September companies com- the gasoline the U.S. consumes. plained that they could not convince a design firm to guaran- In energy terms, distilling ethanol from the sugar in cel- tee to a bank that the finished plant would work. lulose instead of corn is a double play. For corn, the cellulose Certain organisms being tried may improve the odds. Io- itself can be thought of as nearly “free”— it takes very little gen, whose process exploits a fungus from Guam that com- If companies can spawn enzymes in sufficient amounts, cellulose ethanol could extensively displace gasoline. more work to harvest the stalk and requires no extra fertil- pany scientists refer to as “jungle rot,” has tinkered with the izer. Farmers say they must plow under some of the stalks, organism’s DNA so it produces more of the needed enzyme. cobs and leaves to reinvigorate the soil but can harvest most Other investigators are using enzymes made by mushrooms. of this plant matter. Switchgrass, the favored grass for etha- Last fall Honda said it might have found a new bug for the nol, requires minimal fertilizer. job. Agrivida in Cambridge, Mass., is trying to bioengineer Second, when the sugar is removed the remaining mate- corn that contains enzymes that make it break down more rial, lignin, burns well. The North American research leader readily to ethanol. in cellulose ethanol, Iogen Corporation in Ottawa, Ontario, Nevertheless, U.S. Energy Secretary Samuel Bodman said predicts that when it builds a commercial-scale plant, energy at a September roundtable with reporters that the technology from burning the lignin will provide enough surplus heat to might be commercially viable within five years. More compa- boil water to generate electricity. Rather than robbing food nies should be lured in part by generous government incentives, crops to make fuel, cellulose ethanol begins with agricultural even though no one seems quite ready to build on a commer- waste and ends with two marketable products: transportation cial scale. fuel and electric power. Net emissions of carbon dioxide per In the meantime, relying on ethanol from corn is an un- mile driven from cellulose ethanol are near zero — or perhaps sustainable strategy: agriculture will never be able to supply below zero, if the co-produced electricity displaces coal or nearly enough crop, converting it does not combat global natural gas at a power station. The lignin does give off carbon warming, and socially it can be seen as taking food off peo- dioxide when burned, but growing new corn or switchgrass ple’s plates. Backers defend corn ethanol as a bridge technol- consumes gases. Optimists, including scientists at Iogen, fore- ogy to cellulose ethanol, but for the moment it is a bridge to see adapting their process to progressively lower-value feed- nowhere. stock, including converting the cellulose in paper such as that used in this magazine (after you have finished reading it). MORE TO EXPLORE Problems remain, though. Chief among them is taming Ethanol Fuels: Energy Balance, Economics, and Environmental one of the natural processes that break down cellulose; the Impacts Are Negative. David Pimentel in Natural Resources Research, sugars locked in the fiber cannot be distilled into ethanol un- Vol. 12, No. 2, pages 127–134; June 2003. Available at www.ethanol-gec.org/netenergy/neypimentel.pdf til they are liberated from the lignin. Bacteria or fungi must Updated Energy and Greenhouse Gas Emissions: Results of Fuel produce enzymes to do the job. Those bacteria live in incon- Ethanol. Michael Wang in the 15th International Symposium on Alcohol venient locations, such as the underbrush of a distant jungle Fuels, September 26–28, 2005. or the gut of a termite, and they turn out to be harder to do- Available at www.transportation.anl.gov/pdfs/TA/354.pdf mesticate than yeast was. Convincing them to multiply inside Plan B 2.0: Rescuing a Planet under Stress and a Civilization in Trouble. the unfamiliar confines of a 2,000-gallon stainless-steel tank Expanded and updated edition. Lester R. Brown. W. W. Norton, 2006. is tricky, as is controlling their activity in the industrial-scale 25  ’25 Vision on renewable energy: www.25x25.org/