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Jun 15, 2009 (Vol. 29, No. 12)

Alternative Feedstocks Boost Ethanol Production

Industry Increasingly Relies upon Cellulosic Biofuels to Meet Government Mandates

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    Qteros’ Q Microbe, a strain of Clostridium phytofermentans, was harvested from soil near the shores of the Quabbin Reservoir, the 400-billion-gallon reservoir that provides water to Boston.

    Members of the biofuels industry are ready to meet the challenge of producing replacements for petrochemical fuels that will be cost-competitive and renewable, and will meet the increasingly stringent demands of the green revolution. This was the consensus at CHI’s recent “Advanced Biofuels Development Summit.”

    Optimism pervaded the presentations of biological, biochemical, genetic, and microbial strategies for enhancing corn ethanol production, developing cellulosic ethanol products, and innovating methods for producing advanced biofuels. The speakers appeared to be in agreement that no one technology will win out; instead, a variety of viable current and emerging technologies will contribute to meeting biofuel needs.

    Geography may determine which type of biofuel technology is most readily adopted in a specific region, depending on what type of feedstock and biomass is locally available, thereby maximizing local resources and minimizing the energy and cost required to transport these resources.

    Michael Blaylock, Ph.D., vp of systems development at Edenspace Systems, reported on the status of Energy Corn™, a feedstock designed to lower the cost of producing cellulosic biofuels from corn stover. The company’s technology platform, based on identifying promising cellulose genes, transforming crop plants with candidate genes, and evaluating the effects on growth, yield, and cellulose hydrolysis would be applicable to a variety of energy crops including switchgrass, sorghum, and sugar cane.

    Edenspace has demonstrated targeted enzyme expression and activity, with no evidence of negative effects on plant health. Enhanced glucan conversion with a reduced need for cellulose loading allows Energy Corn to yield cost savings, according to Dr. Blaylock. He described corn and corn stover—products of an annual domesticated crop in abundant supply, with low marginal costs of production, low acceptance barriers to farmers, and relative ease of bioengineering—as “the most promising near-term, high-volume source of cellulosic biomass for ethanol” and “a bridging crop between first- and second-generation bioethanol. High-biomass perennial crops such as miscanthus and switchgrass offer excellent longer-term potential,” he added.

    Ethanol can be extracted, with varying degrees of complexity, from all three main components of corn: the endosperm, the germ, and the fiber—the latter two yielding cellulosic ethanol. Cellulose is key for U.S. fuel needs, according to Scott Kohl, technical director at ICM, who suggested that excess cellulose currently available in the U.S.—which includes corn fiber, switchgrass, corn stover, wheat straw, wood waste, and energy crops—could be sufficient to replace imported petroleum products.

    The main economic barrier to increased cellulose production is the current high operating expenses associated with enzyme hydrolysis, according to Kohl. The next-most critical barrier to commercialization of cellulosic ethanol is the need for organisms capable of efficient fermentation of holocellulose, which contains up to 40% C5 sugars.

    Kohl asserted that a genetically modified organism (GMO) will most likely be needed, increasing the cost and time of the regulatory approval process. One of the ways to offset these costs is to target demand for other byproducts of fermentation such as succinic acid, butanol, lactic acid, and higher-value chemicals including acetaldehyde, acetic acid, acetone, and glycerol.


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