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  1. 1. Butanol “During the first half An Energy Alternative? According to the National Renewable Energy Laboratory (NREL), “biobutanol” had of the 20th century, previously been produced through a fermentation By Kristin Brekke the production process known as “ABE,” named such because Though ethanol and it produced Acetone, Butanol, and Ethanol in of butanol from biodiesel are driving roughly 6:3:1 ratios. Clostridium strains were America’s progress on the the fermenting organisms to create the chemicals biological sources road of renewable fuels, from molasses-type feedstocks. This ABE process was a commercial some attention is being nearly disappeared in the 1960s because it could generated by butanol, a not compete on a cost basis with the economical reality - and this is fuel whose promoters creation of solvents from cheap, plentiful petroleum. what today’s butanol believe can become a real player in the world of energy alternatives. The current market for butanol is largely supporters are industrial, for use as a plasticizer or solvent. hoping can What is butanol? How is it produced? And The world market for butanol is estimated at 350 how should the ethanol community feel about this million gallons per year, with the U.S. accounting happen again.” potential alternative fuel? for about 220 million of that. The average cost for a gallon of butanol is between three and four dollars. Butanol defined Butanol is a 4-carbon alcohol. Other chemicals New partnership believes in “next generation” in the alcohol family include methanol (1-carbon), of biofuels ethanol (2-carbon), and propanol (3-carbon). Today Butanol has been generating some attention as butanol is typically produced from petroleum a potential alternative fuel, akin to ethanol but sources, but that has not always been the case. with added benefits, its promoters argue. During the first half of the 20th century, the A heavy-hitting partnership between energy giant production of butanol from biological sources was BP and science innovator DuPont to bring “the a commercial reality - and this is what today’s next generation of biofuels” to the marketplace, the butanol supporters are hoping can happen again. first being biobutanol. 36 EthanolToday S March 2007 EthanolToday S March 2007
  2. 2. In June 2006, BP and DuPont announced a “Initial production of biobutanol will be “A heavy-hitting creation to develop, produce, and market “a next based on an existing technology, enabling generation of biofuels to help meet increasing early commercial market introduction,” the partnership between global demand for renewable transportation companies said in a statement. “In a second energy giant BP and fuels.” In their statement to the press, the phase, development work on a new biotechnology companies say they have been working together process using a higher conversion technology is science innovator since 2003 to “develop advanced biofuels with already under way.” DuPont to bring properties that can help overcome the limitations of existing biofuels.” They report that in this second phase, ‘the next generation feedstocks for biobutanol will include sugar cane of biofuels’ to the They acknowledge existing biofuels as an or sugar beets, corn, wheat, cassava, and - in the “excellent starting point” and that these fuels future - cellulosic sources much like what the marketplace, the first will “continue to play a major role in the future.” ethanol industry is striving for: energy crops like being biobutanol.” However, BP and DuPont identify these points perennial grasses and agricultural byproducts like of opportunity in order to increase market grain straw and corn stover. The companies say penetration: compatibility with existing fuel they plan for this second phase, the “improved supply and distribution systems, the ability to conversion technology,” to support broader blend in higher concentrations without vehicle commercialization before 2010. modifications, and fuel economy. The first product on their agenda - Butanol’s benefits biobutanol - which they believe will address What are the properties of butanol that make each of these issues. BP and DuPont convinced that it’s a fuel worthy of development? BP and DuPont report they are targeting biobutanol for introduction this year in the One of those qualities is butanol’s low Reid United Kingdom, where the companies are vapor pressure (RVP), a rating of .33 psi versus working with British Sugar, a subsidiary ethanol’s 2 psi and gasoline’s 4.5 psi, meaning of Associated British Foods, to convert the butanol has lower evaporative emissions. country’s first ethanol facility to one that produces biobutanol. Another property touted by butanol developers is its British Thermal Unit (BTU) content. March 2007 S EthanolToday 37
  3. 3. Butanol contains 110,000 BTUs per gallon, closer Production breakthrough reported to gasoline’s 115,000 BTUs, meaning there may be Environmental Energy, Inc.(EEI), an Ohio little compromise on fuel economy. company led by David E. Ramey, reports on its website that it has developed BP and DuPont also report that butanol can a process which makes “fermentation-derived be blended at higher concentrations in gasoline butanol more economically viable and competitive than existing biofuels without modifications to with current petrochemical processes and with the auto engines. Butanol is considered “substantially production of ethanol.” similar” to gasoline for blending purposes and is certified by the U.S. Environmental Protection EEI’s website says recent technology advances Agency as a blending agent up to 11 percent. have made it possible for corn and other biomass Environmental Energy, Inc., a U.S. company with feedstocks to be cost-effective sources of butanol a patent for biobutanol production, maintains that derived from fermentation. Prior to its work, the butanol can be used as a total replacement for company says, butanol production from corn and gasoline - 100 percent, gallon for gallon. other biomass feedstocks had been hindered by low yields and low concentrations. For more information: Also, according to NREL, butanol is more Environmental Energy, Inc. “hydrophobic” than ethanol, meaning it has a “EEI’s patent changes everything,” the higher tendency to repel water. This quality allows company reports. “We are now able to produce it to blend well with gasoline, could be used to yields of 2.5 gallons of butanol per bushel of corn.” BP-DuPont biobutanol partnership improve ethanol / gasoline blending, and might mean it’s potentially suitable for transport The company says its new process creates Biofuels/en_US/index.html in pipelines. biobutanol from corn without also producing Acetone or Ethanol, as in the former “ABE” 38 EthanolToday S March 2007
  4. 4. process. In addition, its process generates The unknowns hydrogen which the company believes According to analysis done by the will receive future attention as an National Renewable Energy Lab, most alternative fuel in and of itself. of the advantages of butanol come from its properties as a fuel, not from current The cost? “Our preliminary cost production technology. Traditionally, low estimates suggest that we can produce yields - in the 15 to 25 percent range - biobutanol from corn for about $1.20 have plagued butanol production. Toxicity per gallon, not including a credit for the is also a problem, with butanol being toxic hydrogen produced.” at the rate of 20 grams per liter. With dilute product concentrations of 1 to 2 Between July 14 and August 15, 2005, percent, the distillation technology has EEI’s David Ramey took to the road to traditionally been quite costly. promote butanol as an alternative fuel, driving from Ohio to California and back Another question relates to the fuel on 100 percent butanol fuel. certification process that may be necessary through the EPA. According to NREL, it A July 2005 Green Car Congress is uncertain whether higher concentrations article notes that in his butanol production of butanol or a dedicated butanol fuel method, Ramey takes the approach of would need to undergo Tier 1 and Tier using two types of microbes in two 2 health effects testing, which can be a separate process steps. The first pass costly and time-consuming processes. optimizes the production of hydrogen and butyric acid, while the second pass In addition, it seems that biobutanol converts this acid into butanol. Each step production is largely unproven, especially utilizes a different Clostridium strain. in any substantive quantities. EEI’s The article reports that other processes website reports that the company is had also tried the use of multiple bacteria scaling up to implement a demonstration strains, but within the same slurry, making pilot plant, then a “serious pilot plant” Ramey’s separation approach unique. capable of producing 50 to 100 gallons per week is the next step forward. Even The patent EEI holds is U.S. No. for its promotional butanol drive cross- 5,753,474: “Continuous Two Stage, Dual country, EEI purchased conventional Path Anaerobic Fermentation of butanol from a chemical company to fuel Butanol and Other Organic Solvents its trip. Using Two Different Strains of Bacteria.” Many unknowns remain for the future Some of the EEI work has been done of butanol. Certainly the work of BP and through a U.S. Department of Energy DuPont and of Environmental Energy, Inc. research grant, a collaboration between - and any others who enter the butanol Ramey and Shang-Tian Yang, Department efforts - will be observed with interest. of Chemical and Biomolecular Engineering at Ohio State University. Will butanol production reach a cost- effective level? Will it reach commercial- As BP and DuPont report intending scale viability? If these milestones to use existing butanol production are achieved, does it compete with or technologies first before moving into the complement ethanol? At this point, it’s next phase of biomass butanol production, more questions than answers on the EEI’s plan initially calls for selling butanol front. butanol into the existing commercial solvents marketplace to provide a revenue stream before moving into butanol for the transportation sector. March 2007 S EthanolToday 39