Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0912073107 (2010)

Finding a safe, low-cost and high-yield way to break down cellulose — a major component of plant-fuel sources such as maize stalks — into fermentable sugars is a challenge in biofuel development. A mild mixture of acid and ionic solvent may prove quicker and cheaper than the enzymes commonly used.

Ronald Raines and Joseph Binder at the University of Wisconsin, Madison, improved an existing recipe by slowly adding water to a mixture of acid catalyst and ionic liquid as it attacked untreated cellulosic biomass. The process avoids the hazards of working with concentrated acids, and in a few hours produces sugar yields of 70–90%, which enzymes take days to achieve.

However, scaling this up for commercial use could be problematic because of the need to recycle ionic liquids, which are expensive relative to other solvents.