Table 2. Planned and exisTing cellulosic eThanol PlanTs in norTh america (continued) name
location
capacity (million gal/yr)
startup
Southeast, U.S. *
capacity start(million up gal/yr) 55 2012 15 2014
Terrabon
Bryan, Tex.
0.1
*
Pontotoc, Miss. Edmonton, AB Tenn.
20 9.5 25
U.S. Sugar Vercipia West Biofuels
Clewiston, Fla. Highland Co., Fla. Yolo Co., Calif.
100 36 0.182
2013 2012 *
name
location
Coskata, Inc. DuPont Danisco Cellulosic Ethanol Enerkem Enerkem Genera (DDCE, UTenn.)
2012 2012 2012
Source: Biotechnology Industry Organization
* Not available
octane number, n-butanol has many potential uses for making chemicals, says CEO Rick Wilson. “As a chemical, n-butanol sells for around $6/gal as opposed to $1.90/gal for fuel.” In January, Cobalt launched its first pilot-production facility, which has a 20 m.t./d hydrolysis unit and a fermentation reactor capable of producing 2–3 gal/d of butanol. We are on track to build a commercial facility within two years, says Wilson. The process begins with a pretreatment step whereby wood is hydrolyzed in dilute acid and an acid promoter, which releases the sugars from the wood. Hydrolysis only takes a few minutes as opposed to days need by enzymes, he says. After hydrolysis, the sugars are converted to n-butanol in a patented, continuous fermentation process. Instead of yeast used for making ethanol, or genetically modified yeast for making iso-butanol, Cobalt’s process uses bacteria in biofilms on a support. Similar to a bioreactor used for wastewater treatment, the reactor continuously circulates the feed solution through the bioreactor. This continuous fermentation is about 30 times faster than batch fermentation. The system is controlled to remove product before the concentration becomes too high to poison the bacteria. The n-butanol is then purified by a process involving both distillation and phase separation. The n-butanol/water solution is highly non-ideal, and simulations have been used to develop a separation process, which has several advantages. At low concentrations, the n-butanol comes off first. Secondly, the heat of vaporization is half that of ethanol, so less energy is needed for the distillation. Thirdly, a phase separation occurs at a certain concentration that allows us to bypass the azeotrope, so no molecular sieves are needed to achieve the final purity — another cost factor with ethanol, explains Wilson. The company is focused on wood feedstock (both hardwoods and soft). Last month Cobalt announced its first butanol from beetle-killed pine wood.
“This is a very cheap feedstock — there’s lots around and some even pay you to take it,” he says. Colorado’s pine forests have been devastated by mountain pine beetle, which has infested
nearly half of the state’s 5-million acres of pine forest. Cobalt is working with the Colorado State University for fuel testing. n Gerald Ondrey
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