Making Biofuel from Microalgae

Increasingly, consumers are being urged to imagine a future when their vehicles and commercial machinery are powered not just by gasoline or traditional diesel but also by liquid biofuels; electricity generated by wind and solar; and, perhaps, even hydrogen. Ethanol, a gasoline replacement usually made with corn in the United States, already replaces nearly 10 percent of U.S. gasoline. But researchers have made a strong case that multiple types of biomass feedstock are needed to create adequate supplies of biofuel.

The report “Biomass Feedstock For a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply,” published in 2005 by U.S. Department of Energy and Department of Agriculture researchers, has just been revised. Widely known as the “billion-ton study,” the update indicates that as much as 1.6 billion tons of terrestrial biomass from agricultural wastes, forestry waste, municipal solid wastes and energy crops such as miscanthus and switchgrass could be harvested sustainably in the United States annually for biofuels, bioenergy and bio-based products. Considering the theoretical fermentation yields on biomass sugars and the energy content of ethanol, this projection also establishes the theoretical maximum production of bio-based gasoline equivalents at close to 96 billion gallons. Since the United States uses approximately 140 billion gallons of gasoline, 40 billion gallons of road diesel and 20 billion gallons of jet fuel (all derived from crude oil) per year, it is clear that biofuels based on terrestrial feedstocks can never meet that demand. At the National Renewable Energy Laboratory (NREL), where we conduct our research, we concluded the same thing when the original billion-ton study was released. That prompted us to rebuild the Aquatic Species Program, previously funded from 1978 to 1996 by the U.S. Department of Energy, to evaluate the potential of algae-based biofuels.