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.

Relative GHG emissions reduction potentials for ethanol by feedstock type. These estimates refer to direct emissions only, and do not include emissions from land use change. Source: Worldwatch Issue Brief: U.S. Biofuels: Climate Change and Policies (PDF file)

Contents

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 limitations on the commercialization of cellulosic ethanol. (Citation needed)
  • Cellulosic ethanol has many advantages however:
  • 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

Events

2010

2009

Publications

See books, reports, scientific papers, position papers and websites for additional useful resources.

News

2010

2009

  • (China) Biofuels: learning from Obama, 21 August 2009 by China Dialogue: "China already has the foundation it needs to commercialise cellulosic ethanol production. [For instance,] China was previously a world leader in acid and enzyme hydrolysis."
    • "In accelerating the development of biofuel energy, China must coordinate on a national level and concentrate on two aspects....First, while commercialising mature technology as soon as possible, China should also strengthen basic research in key fields."[4]
  • Bacteria for Better Biofuels, 30 March 2009 by Scienceline: Scientists "have found a unique way to increase the growth of one promising biofuel source on marginal land: just add bacteria."
    • "'If we have bacteria that can help plants to grow better, then these plants will be able to get established [on marginal land], and we can then use these soils for the economic production of biofuels,' says Daniel van der Lelie, a microbiologist at Brookhaven National Laboratory on Long Island, NY and lead author of a study published in the February 1 issue of the journal Applied and Environmental Microbiology."
    • "In the study, the researchers focused on improving the growth of poplar trees. These trees are known for their rapid growth and ability to survive in many different types of climates, both ideal traits for biofuel production. The Brookhaven group found that adding the right kinds of naturally occurring bacteria to the roots of poplar trees increased their biomass production by up to 80 percent over ten weeks, according to van der Lelie."[7]
  • Cellulosic Ethanol May Benefit Human Health And Help Slow Climate Change, 3 February 2009 by ScienceDaily: "Filling our fuel tanks with cellulosic ethanol instead of gasoline or corn-based ethanol may be even better for our health and the environment than previously recognized, according to new research from the University of Minnesota."
    • "The study finds that cellulosic ethanol has fewer negative effects on human health because it emits smaller amounts of fine particulate matter, an especially harmful component of air pollution."
    • "The study is the first to estimate the economic costs to human health and well-being from gasoline, corn-based ethanol and cellulosic ethanol made from biomass. The authors found that depending on the materials and technology used in production, cellulosic ethanol's environmental and health costs are less than half the costs of gasoline, while corn-based ethanol's costs range from roughly equal to about double that of gasoline."
    • "The paper also points out that other potential advantages of cellulosic biofuels, such as reducing the amount of fertilizer and pesticide runoff into rivers and lakes, may also add to the economic benefit of transitioning to next-generation biofuels."[9]
    • See the Open Access study, "Climate change and health costs of air emissions from biofuels and gasoline" in the Proceedings of the National Academy of Sciences.
  • GM voices commitment to biofuels as study touts possibilities, 10 February by Kansas City Star:
    • "A top General Motors executive said Tuesday his company remains committed to the use of biofuels, including cellulosic ethanol, even with such options as electric cars becoming available."
    • "The comment coincided with the release of a study reporting that the U.S. eventually could produce enough ethanol to meet one-third of the country’s demand for gasoline. The study by Sandia National Laboratories, a federal research lab assisted by GM’s technical staff, concluded that 90 billion gallons of biofuel — mainly cellulosic ethanol — could be produced annually by 2030."
    • "The study assumed that cellulosic energy would be the principal biofuel and said it would take 48 million acres to grow such necessary feedstock as wood and switchgrass. The study also said those products should not be land now used to grow food." [10]
  • Range Fuels gets $80M loan commitment, 19 January 2009 by Denver Business Journal.
    • "Range Fuels Inc. said Monday it’s received a conditional commitment for an $80 million loan from the U.S. Department of Agriculture to help build the company’s commercial cellulosic ethanol plant near Soperton, Ga."
    • "Range Fuels uses a proprietary, two-step conversion process using heat and chemicals to convert biomass — such as wood chips, switchgrass and other carbon-based waste items — into ethanol. The Georgia plant will use wood and wood waste from that state’s pine forests and mills as its feedstock and is expected to have the capacity to produce more than 100 million gallons of ethanol a year." [11]

2008

  • Obama, Vilsack and Salazar: The Ethanol Scammers’ Dream Team, 29 December 2008, by Energy Tribune:
    • "The math is straightforward: to produce 32 billion gallons of cellulosic ethanol would require the annual harvest and transport of 320 million tons of biomass. Assuming each trailer holds 15 tons of biomass, that volume of biomass would fill 21.44 million semi-trailer loads. If we further assume that each trailer is 48 feet long, the column of trailers holding that quantity of feedstock would stretch almost 195,000 miles – that’s nearly the distance from the earth to the moon."
    • "The corn ethanol industry is a scam. Cellulosic ethanol is a sham. And yet Obama and his appointees continue to promote the false notion that these fuels are the answer to America’s energy challenge." [12]
  • 25x'25 Offers Congress, New Administration Recommendations To Spark Economic Recovery, 15 December 2008 Press Release:
    • "The National 25x'25 Alliance Steering Committee today presented to Congress and the incoming Obama administration a wide-ranging package of new recommendations that will bolster the U.S. economy, create new jobs and insure a clean energy future."
    • "The 12 recommendations boost federal renewable energy programs by calling for additional investments totaling some $4.14 billion, an outlay that could ultimately help generate hundreds of billions in new annual revenues and millions of new jobs."
    • "The package also calls for a renewed look at government support for advanced biofuel production, including increased funding in the form of grants specifically aimed at the construction of commercial-scale, cellulosic production facilities. The proposals underscore the critical role USDA and its programs can and will play in the promotion of a clean energy future and a robust economy." [14]
  • 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."
  • 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.'"[15]
  • 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."[16]
  • 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.'"[17]

2007

2006

  • Stover to Fill Part of Ethanol Goal for US 22 November 2006 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.

References

1Biofuels for Transportation (draft) (2006, Worldwatch Institute), p.10-12. Used with permission.

Cellulosic ethanol edit

Cellulosic feedstocks: Bamboo | Mesquite | Rice | Switchgrass

Ethanol edit
Bioethanol - Corn ethanol
Ethanol producers by country | Ethanol feedstocks: Cellulosic ethanol (Microbe research) | Ethanol policies: Ethanol subsidies


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