Outlook for Bioethanol Production from Lignocellulosic Feedstocks: Technology Hurtles

Ethanol is used today as an alternative fuel, a fuel extender, an oxygenate, and an octane enhancer. From just over 10 mi/lion gallons of production in 1979, the U.S. fuel ethanol industry has grown to more than 1.8 billion gallons of annual production capacity. These commercial operations use technology that converts com starch to sugars, which are then fermented to ethanol. Throughout this time, the U.S. Department of Energy has invested in R&D technology that will allow the fuel ethanol industry to : expand production using lignocellulosic feedstocks. However, unlike starch, cellulose is highly resistant to enzymatic degradation. It is now clear that cutting-edge biochemical technologies must be used to reduce the cost of cellulase activity delivered to the bioethanol process. We estimate that cellulase usage would contribute around $ 0.60 to the cost of making one gallon of ethanol using currently available technology. These costs must be reduced ten-fold by 2015. Technically, this objective requires a ten-fold increase in enzyme specific activity or production efficiency or some combination thereof.