The Science
Isobutanol is a promising biofuel with advantages over ethanol: it holds more energy, is less corrosive, doesn't evaporate as fast when blended with gasoline, and can be upgraded into other products like jet fuel. But making isobutanol from non-food plant fibers is challenging. This study estimated a biorefinery could produce isobutanol for a break-even price as low as $14.40 for the energy equivalent of a gallon of gasoline and showed how improvements in some parts of the process could cut that cost by nearly half.
The Impact
Transportation is the largest source of heat-trapping gases that contribute to global climate change. Liquid fuels made from plants such as sorghum, poplar, and switchgrass grown on non-agricultural lands have lower net carbon emissions than fossil fuels and provide economic benefits to rural communities, offering a sustainable drop-in fuel for airplanes, ships, and other vehicles that are hard to run on electricity.
Summary
Using a genetically modified strain of yeast to ferment poplar, sorghum, and switchgrass treated with a γ-valerolactone (GVL)-based process, scientists with the Great Lakes Bioenergy Research Center achieved isobutanol yields as high as 94% of the theoretical maximum.
Technoeconomic analysis of a hypothetical biomass-to-isobutanol refinery showed a minimum fuel selling price (MFSP) of $14.40–$16.01 per gasoline gallon equivalent, with sorghum resulting in the lowest price. Sensitivity analysis showed that solvent/biomass ratio during pretreatment and enzyme loading during hydrolysis have the greatest impact on production cost, and improvements of those can reduce MFSP by 46%.