Cellulosic ethanol
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Cellulose (C6H10O5)n is a complex carbohydrate (a long-chain polymeric polysaccharide of beta-glucose)that forms the main constituent of the cell wall in most plants. It is the most abundant form of living terrestrial biomass. Cellulosic biomass has three primary components: cellulose, hemicellulose, and lignin. Lignin and cellulose, considered together, are termed lignocellulose, which (as wood) is argued to be one of the most common biopolymers on Earth. While most animals, including humans can not digest cellulose, some, particularly ruminants (such as cows) and termites, can digest cellulose with the help of symbiotic micro-organisms.
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Cellulosic ethanol
While ethanol production from sugars and starches has been done for thousands of years, the technology to produce ethanol from cellulose is relatively modern and is not yet fully commercialized.
- The conversion process uses enzymes, like cellulase, to break cellulose down to sugars. It is also possible to produce biofuels from cellulosic feedstocks through gasification and biomass-to-liquids technologies.1
- The high cost of these enzymes is one of the main limitation on the commercialization of cellulosic ethanol. (Citation needed)
- Cellulosic ethanol has many advantages however:
- The use of waste biomass, such as forestry wastes, or by-products of the paper industry, allows for ethanol production without increasing agricultural production.1
- Cellulosic biomass from fast-growing perennial energy crops, such as short rotation woody crops and tall grass crops, can be grown on a much wider range of soil types, where the extensive root systems that remain in place with these crops help prevent erosion, and increase carbon storage in soil.1
- Energy crops can often be grown on poorer soils.1
- However, high biomass yields will only be achieved on good soils with sufficient water supply.1
- Cellulosic biomass can be easier to store for long periods of time.1
- Compared to conventional crops, where only small portion of the plant can be used for biofuel production, perennial energy crops can supply much more biomass per hectare of land, since nearly the entire plant can be used as feedstock.1
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Publications
See books, reports, scientific papers, position papers and websites for additional useful resources.
- Grass biofuels 'cut CO2 by 94%', 8 January 2008, by BBC News: A new report by US researchers has found that fast-growing "switchgrass-derived ethanol produced 540% more energy than was required to manufacture the fuel" and "delivers vast savings of carbon dioxide emissions compared with petrol." The paper, "Net energy of cellulosic ethanol from switchgrass (PDF file)" in the Proceedings of the National Academy of Sciences, analyzed all of the energy input factors, including "nitrogen fertiliser, herbicides, diesel and seed production."
- Induction of the celC operon of Clostridium thermocellum by laminaribiose by Michael Newcomb, Chun-Yu Chen, and J. H. David Wu; PNAS, 5 January 2007. This paper identifies how genes responsible for biomass breakdown are turned on in a microorganism that produces [[]]from biomass sources.
- Cellulosic Ethanol - Biofuel Beyond Corn by Nathan S. Mosier; Department of Agriculture and Biological Engineering, Purdue University, December 2006.
- Making Cellulosic Ethanol Happen: Good and Not So Good Public Policy (pdf) by David Morris; Institute for Local Self-Reliance, January 2007.
- Breaking the Biological Barriers to Cellulosic Ethanol: A Joint Research Agenda - A Research Roadmap Resulting from the Biomass to Biofuels Workshop, December 7–9, 2005, Rockville, Maryland; USDOE.
- Biomass as feestock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply - A joint study by USDA and USDOE, April 2005.
- Carbon-Negative Biofuels from Low-Input High-Diversity Grassland Biomass (subscription required) by David Tilman, Jason Hill, and Clarence Lehman; Science Vol. 314. no. 5805, pp. 1598-1600, 8 December 2006.
- Ethanol from Cellulose: A General Review (PDF) by P.C. Badger; reprinted from: Trends in new crops and new uses, J. Janick and A. Whipkey (eds.). ASHS Press, Alexandria, VA, 2002.
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News
- U.S. needs environmental standards for biofuels, 2 October 2008 by mongabay.com: "The U.S. lacks criteria to ensure that cellulosic ethanol production will not harm the environment, warn scientists writing in the journal Science. The researchers say that with proper safeguards, cellulosic ethanol can help the U.S. meet its energy needs sustainably."
- Read the original article here (subscription required)
- Crop Residue May Be Too Valuable to Harvest for Biofuels, 15 July 2008 press release by Washington State University: "In the rush to develop renewable fuels from plants, converting crop residues into cellulosic ethanol would seem to be a slam dunk. However, that might not be such a good idea for farmers growing crops without irrigation in regions receiving less than 25 inches of precipitation annually, says Ann Kennedy, a USDA-Agricultural Research Service soil scientist".
- "If residue were harvested, she said, soil fertility would drop and farmers would have to find other ways to increase the amount of organic matter in their soils."
- "'We need to constantly replenish organic matter—so removing valuable residue, especially in areas with low rainfall, may not be the best practice.'"[1]
- Shell boosts stake in Iogen cellulosic ethanol, 15 July 2008 by Reuters: "Oil major Royal Dutch Shell Plc said on Tuesday it will make a 'significant investment' in a venture it has with Canadian cellulosic ethanol maker Iogen Corp."
- "Iogen, which is also backed by Goldman Sachs Group Inc, has run a demonstration plant in Ottawa since 2004 that can produce about 2.5 million liters of ethanol a year from the plant stalks that are left behind after farmers harvest crops."
- "It is planning to open a C$500-million ($500 million) commercial-scale plant in Saskatchewan, Canada's largest wheat-producing province, in 2011. That plant would produce about 90 million liters (23.78 million U.S. gallons) of ethanol a year.
- "Cellulosic ethanol costs about twice as much to produce as corn-based ethanol, and has not yet been produced on a commercial scale."[2]
- The race for nonfood biofuel, 4 June 2008 by the Christian Science Monitor: With "gas now at $4 a gallon and critics hammering corn ethanol for helping to pump up global food prices, it is clear that the holy grail of biofuels – cellulosic ethanol – needs to make its entrance soon."
- "A big step forward came last week with the opening of the nation’s first demonstration-scale cellulosic ethanol plant in Jennings, La. The facility, built by Cambridge, Mass.-based Verenium Corp., will use high-tech enzymes to make 1.4 million gallons per year of ethanol from the cellulose in sugar cane bagasse, a waste product."
- "Still, some environmentalists are hesitant about endorsing cellulosic technology without qualification, since there could be 'good cellulosic and bad cellulosic,' says Nathanael Greene, senior policy analyst at the Natural Resources Defense Council in New York."
- "'We’ve got to pay attention to the performance of new biofuels, not give credentials out for who produces the most gallons,' he says, 'but who produces the best in terms of water use, water quality, soil erosion, wildlife and habitat enhancement – and greenhouse-gas emissions.'"[3]
- Green Star secures algal biodiesel license, 31 January 2008, from Biofuel Review. A license was granted to use the process developed by Green Star to convert algae biomass to biodiesel, and to use cellulose sugars to produce ethanol.
- Xethanol increases Cellulosic Ethanol Production Rates, 16 January 2008, from Renewable Energy Access, new developments have increased yields by as much as 21%.
- Genencor launches first ever commercial enzyme for cellulose ethanol. "Genencor, a division of Danish company Danisco A/S, announced the launch of Accellerase 1000, the first ever commercially available biomass enzyme developed specifically for second generation biorefineries. "
- Cellulosic Ethanol Takes Off! Engineering commences for the first US pulp mill based biorefinery 23 January 2007 from American Process, Inc. Flambeau River Biorefinery, LLC of Wisconsin has entered into a Memorandum of Understanding with American Process Inc. of Atlanta, Georgia to provide project management and engineering services for its cellulosic ethanol project at Park Falls, Wisconsin.
- Sunopta Updates on Cellulosic Ethanol Projects 18 January 2007 from Greencarcongress.com. SunOpta Inc. provided an update on the status of four cellulosic ethanol projects using a variety of cellulosic biomass including woodchips, corn stover, sugar cane bagasse, and wheat straw. The projects are in China, Spain, Canada and Louisiana.
- Are We There Yet? Not quite, but cellulosic ethanol may be coming sooner than you think 11 Dec 2006 from Grist. This piece examines trends in the development of cellulosic ethanol and suggests we may have a commercial industry within 5 years.
- Mascoma Corporation Inches Closer to Commercially Producing Cellulosic Ethanol 12 December 2006 from Biofuels Journal.
- Company brings in High-Yield Trial Rice Straw Harvest; Targets Cellulosic Ethanol Production for 2007 20 November 2006, from greencarcongress.com. Colusa Biomass Energy Corporation has completed its first ever rice-straw harvesting operation in California, the US' second-largest rice producer. It collected 6,800 tons of rice straw with an average yield per acre harvested of over 4 tons/acre, compared to previous assumptions of 2.5 tons/acre. The higher yields significantly reduced the amount of acres necessary to be harvested in order to reach CBEC’s target volume of rice straw. Colusa will turn the rice straw into ethanol at its plant, which is due to be finished in 2007.
- First Commercial-sized Cellulosic Ethanol Plant in US to be built in Iowa 21 November 2006 from the Des Moines Register. The Broin Cos. plant will be converted from a 50 million-gallon-a-year conventional corn dry mill facility into a 125 million-gallon-a-year commercial-scale biorefinery producing ethanol not only from corn but also corn stalks, leaves and cobs. The $200 million plant expansion is scheduled to begin in February and take about 30 months to complete. Iowa already has 25 ethanol plants producing about 1.6 billion gallons of ethanol, more than any other state.
- Stover to Fill Part of Ethanol Goal for US 22 November from the Des Moines Register. A report issued by the Biotechnology Industry Organization on Tuesday estimated that it was "realistic" to harvest 30 percent of the available stover nationwide to yield 5 billion gallons of ethanol. Most of the stover would continue to be left in the field for environmental reasons as the decaying plant material prevents soil erosion and adds ground nutrients. The US DOE has set a goal of 60 billion gallons of ethanol by 2030. However that goal assumed the use of 70% of stover for ethanol.
- Texas Mesquite Trees Considered for Cellulosic Ethanol October 20, 2006 by MSNBC. "The Texas A&M Agricultural Research and Extension Center in Lockett is working on a project dubbed the "Mesquite Alternative Fuel Project," which will study the feasibility of harvesting mesquite and turning it into cellulosic ethanol." There are 52 million acres of mesquite in texas and it is considered perfect for harvesting because of its high regrowth rate.
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References
1Biofuels for Transportation (draft) (2006, Worldwatch Institute), p.10-12. Used with permission.
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