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Feature Articles : Jun 1, 2007 ( )
Cellulosic Biofuels Abound with Promise
Conversion Processes Are Being Developed for Nonfood Crops to Obviate Corn Dependency!--h2>
While ethanol is being heralded as the solution to the world’s energy concerns, developers are scrambling to replace corn in the U.S. with more economical feedstocks and to develop more efficient production methods. “Everybody has to look beyond oil,” insists Jim Watson, Ph.D., managing director at BioJoule (www.biojule.co.nz). They have to look beyond corn, too.
“Right now, the U.S. produces five billion gallons of ethanol annually, and 95 percent of that is from corn grain,” elaborates Kevin Gray, director of alternative fuels for Diversa (www.diversa.com). That’s because the starch in the kernels is a form of glucose that can be hydrolized and fermented fairly easily.
Unfortunately, diverting 17% of the U.S. corn crop to biofuel drove corn prices to more than $4 per bushel, which has rippled throughout the economy—animal feed costs have soared, farmers have slaughtered their hogs and chickens, and prices for soft drinks and other products using corn syrup have increased. “We’ve seen similar price escalations with sugar in Brazil and rapeseed in Europe,” notes Laurence Alexander, vp analyst, Jefferies & Co. (www.jefferies.com). To counteract that, researchers are developing conversion processes for nonfood crops like trees, grasses, algae, and corn stover (the stalks and leaves).
“Using the corn fiber—the husks and cobs—could increase yields about 10 percent, and it is already in the mill,” notes Argonne National Laboratory’s (www.anl.gov) Seth Snyder, Ph.D., section leader of chemical and biological technology. Using corn stover, which farmers typically leave in the field and plow under, could increase yields 50–100%, he adds. And, “there are some large opportunities in wood,” based only partially on density per acre, year-round harvestability, and an established forest products industry.
“The problem with cellulosic biomass is that it’s hard to digest,” Gray says, making it an expensive feedstock.
Diversa is working on that issue by developing high-activity enzymes to increase the rate of cellulosic conversion. It has already developed a thermally robust amylase enzyme for corn stover. Discovered around smokers in the sea floor several years ago, this new enzyme is proving adept in breaking down cellulosic biomass.
Other efforts are aimed directly at processing costs and include enzymes that run at various pH levels, work at lower temperatures, or require less energy to make cellulosic biomass conversion competitive with grain-based feedstocks. Beyond the enzymes, Diversa is studying the biochemical pathways used by microbes in the guts of ruminants, like cattle and deer, and wood-boring insects like termites, which normally convert 95% of the wood they ingest into fermentable sugars within 24 hours.
“The enzyme cost, especially in biomass, is one of the largest components,” Gray notes. “If one could produce the enzymes in the raw material it could significantly lower the cost of processing.” That notion is being advanced in a joint project with Syngenta (www.syngenta.com), in which a strain of corn expresses high levels of alpha amaylase for a “self-processing” feedstock. Commercialization is expected in 2008. “The goal is to produce celluloses directly in raw material, using a multienzyme mixture to convert cellulose to sugar,” Gray adds.
Cellulose Processing Plants
This spring, the U.S. Department of Energy awarded $76 million to Abengoa Bioenergy (www.abengoabioenergy.com) and its technology partner, Dyadic International (www.dyadic.com), to develop a 11.4-million gallon cellulosic ethanol plant. The three-step process relies upon acid hydrolysis, steam, or other usual methods to crack open the biomass into cellulose, xylan, and lignin. Burning the lignin for energy, the facility will transform cellulose and xylan into a fermentable mixture, using six to eight enzymes. When sugar is added, the result is ethanol, butanol, or polymers.
Dyadic’s particular expertise lies in developing a highly efficient Chrysosporium lucknowense (C1) fungi to produce enzymes. Inefficient in the wild, C1 was engineered to make 200–400 times more cellulose enzymes than the wild type. In the process, its morphological structure changed, increasing its strength and resulting in a single-celled colony that experienced less shear during processing and led to shorter cycle times and decreased energy use. It handles a wide pH range, from 4.5–9.0; temperatures of 25–43°C; and produces 100 L of protein with five days of fermentation.
Dyadic uses the same fungi strain from lab through full production. “Last year, we scaled from 1 microliter to 150,000 liters without changing the cell line,” Mark Emalfab, CEO, says. “We can insert DNA at will to turn genes on and off, and up- and down-regulate genes of the fungi. Of the approximately 11,000 genes in the genome, we’ve identified 120 carbohydrates and, of those, about 60 are useful in biomass conversion,” he says.
Because enzymes are highly specific, having a variety will be helpful, as no dominant feedstock is unlikely to emerge. Instead, Alexander says, “There will be a patchwork of feedstocks,” with dominant regional players.
In New Zealand, an effort is being made to develop the cane willow as a feedstock. BioJoule is developing commercial nurseries to grow this hardwood to produce ethanol, natural lignin, and xylose. Unlike New Zealand’s famed radiata pine forests, Salix grows well on marginal land and can be coppiced (cut several inches above ground) every two years, according to Jim Watson, Ph.D., BioJoule’s founder. “Salix generates 11 to 16 times more energy than it takes,” he notes.
The ethanol generated from Salix makes a small profit, but the byproducts have value equal to that of ethanol, Dr. Watson says, and allows use of all the biomass. He adds, “We can recycle chemicals, so there’s not a lot of chemical waste.”
Until the Salix crops are available, BioJoule can use green waste from municipal waste streams and landscape companies. “Currently, we’re raising investment capital to complete a pilot plant and are talking with a number of distributors for ethanol and with end users for xylose.” Dr. Watson says that he expects the plant to be running by the end of 2008. Ultimately, the facility will be capable of processing several tons of dry feedstock per day, although “large-scale production is a ways away.”
In the U.S., the U.S. Department of Agriculture’s Forest Products Research Laboratories and several leading universities are advancing hardwood to bioethanol conversion, emphasizing willow and other low-density hardwoods, including poplar, aspen, and cottonwood. In these woods, the lignin is less cross-linked and there is a higher hemi-cellulose content, which make it easier for enzymes to degrade it. (Softwood, in contrast, has highly cross-linked lignin, long fibers, and recalcitrant cellulose crystals, all of which make it hard to degrade.)
Algae may offer an alternative to cellulosic biomass or grain. “Algae is easy to break down and less energy is spent growing it” than other crops, analyst Alexander says. It also provides a ready use for the CO2 generated by coal-fired power plants, helping them become carbon neutral.
The National Renewable Energy Laboratory indicated that, theoretically, growing the equivalent of 15,000 gallons of oil per acre per year was possible in open ponds. That’s about 30 times more oil than land-based plants, according to the U.S. Department of Energy’s Aquatic Species Program: Biodiesel from Algae.
Global Green Solutions (www.globalgreensolutionsinc.com) believes it can produce 180,000 gallons of oil per acre per year by using vertical bioreactors in greenhouses to increase the density per acre and to better control such issues as contamination, evaporation, heating, and cooling. Craig Harting, COO, suggests the costs of the algae oil, scaled to hundreds of thousands of gallons, would be 30% less than the cost of other crop-based feedstocks.
Global Green Solutions is in the R&D phase, installing a small, quarter-acre pilot plant. The operating plan is to produce and harvest algae, extract oil from that, and sell the oil to biodiesel refineries. Biorefineries would like a guarantee of 10 million gallons per year—a 50- to 55-acre facility.
“The process is continuous and completely self-contained,” according to Harting. Water and air are filtered, and the algae replicates four to six times per day. Thanks to the tight controls, Global Green Solutions can select and cultivate individual cells based upon their attributes. “We’re trying to optimize our oil around carbon 13 or carbon 14 chains,” Harting says, noting that there are thousands of strains of algae and many different product opportunities. The native strains Global Green Solutions uses yield about 50% of their weight in oil, with the remainder having value as fertilizer.
The open pond method is favored by LiveFuels (www.lifefuels.com). Plans include growing the algae, which thrives at 23°C, in ponds, first in southern California and later in north central California, according to Lissa Morganthaler-Jones, CEO.
LiveFuels plans to genetically modify native algae to increase lipids and other valuable attributes, working with Sandia National Laboratory, the National Renewable Energy Laboratory, and academic institutions. Current, early work focuses on Botryococcus braunii, which, she says, has 20- to 40-carbon long chains. Other researchers indicate hydrocarbons constitute between about 30–75% of its dry mass. The goal, Morganthaler-Jones says, is “to provide intermediate feedstock.”
Blue Sun (www.gobluesun.com) is taking a different tack, working to hybridize oil seeds to produce more oil. The company is working with winter and spring canola and, for dry land, canelina. “We’ve had about two years of field trials,” researcher Charlie Rife, Ph.D., says, and are seeing increases. CEO and president Jeff Probst expects it to take more than 10 years to develop a few commercial feeder seeds. Once the seeds are optimized, they’ll be planted and much of their seeds will be crushed by Blue Sun for B-100 and B-20 biodiesels. “The cost is about the same as for diesel fuel,” Probst says.
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