Advanced BioFuels USA

by Philip T. Pienkos (R&D Magazine)  … This time, the leading force was not the DOE (U.S. Department of Energy), but the investment community acting in the belief that the power of modern biotechnology could be brought to bear against the hurdles that stymied the ASP (Aquatic Species Program).  Dozens of new startups appeared throughout the years that followed, most focused on specific technologies that were promoted as game changers.  One by one, these companies disappeared, to be replaced by others, though the rate of appearance of new startups has slowed significantly in the past few years.  A few companies that were fully integrated in the processes of cultivation, harvesting, and conversion began to stand out.  These included Sapphire, Algenol, Cellana, Solazyme, Heliae, Solix, and others.  Although progress was made in addressing the technical challenges identified earlier, new ones became apparent including pond crashes (brought on by pests, predators and pathogens), limited resource availability (land, CO2, nutrients, water, etc.), and environmental issues (high evaporation rate, limited sunlight, temperature variability).  These challenges were accompanied by another prolonged drop in oil prices, which again put pressure on the process economics to justify expensive scale up efforts to move outdoors into pilot and demo scale cultivation facilities.

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AT NREL, we have used techno-economic analysis (TEA) to build a model for the production of algal biomass in large open ponds.  This model allows us to determine the economies of scale that can reduce cost as the size of cultivation facilities (basically microalgae farms) increase.  Based on this analysis, we have determined that production costs can drop significantly until a farm reaches about 5000 acres of open ponds, at which point additional area leads to diminishing returns.  At the 5000 acre farm scale, we believe that it is possible to produce biomass based on verified growth rates for approximately $1000 per dry ton, but operating at the smaller scales currently available, the cost would be much higher.  Thus, even economic production of high value products like omega-3 fatty acids is challenging, and economic production of low value products like biofuels is impossible. 

In addition to the expected cost saving from driving towards economy of scale, it is expected that improvements in strain characteristics and cultivation processes will also lead to reduced costs.  Our TEA modeling suggests that achieving a target of $300 per dry ton can be achieved.  Reaching this cost target would enable economic production of a number of higher value products, but biofuel production would still not be able to compete with crude oil.

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Researchers at NREL have taken a page from the petroleum refinery (and the meat packing industry) to propose a multi-product algal biorefinery concept as a means to let no component of the microalgal biomass go to waste.

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Using sulfuric acid and elevated temperatures, we disrupt the algal biomass, hydrolyzing the carbohydrates to monomeric sugars (largely glucose and mannose).  This slurry is pumped into fermentors for conversion of the sugars to fuels and chemicals.  To date we have produced ethanol, succinic acid, and butyric acid using both yeast and bacteria and we are confident that the microalgal sugars can be substituted for corn, cane or cellulosic sugars for any fermentation process.  After fermentation, the product is recovered and the remaining liquor is extracted with hexane to recover the algal lipids.  We have shown that the fermentative organisms are unable to utilize lipids, and that they can be recovered in high yield from the liquor.   READ MORE