Scientists Crack the Processes Occurring during Biomass Pretreatment

Researchers at the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL) have identified two fundamental processes - cellulose dehydration and lignin-hemicellulose phase separation - responsible for the morphological changes in biomass during pretreatment processes used in breaking down woody plant materials for biofuel production.

Pretreatment processes use extremely high temperature and pressure to break apart the protective lignin and hemicellulose polymers that surround cellulose fibers in the biomass. Once released, cellulose can be enzymatically degraded into simpler sugars, and then fermented into ethanol. Understanding the mechanism of biomass breakdown during pretreatment will lead to more efficient conversion of biomass into ethanol.

By integrating experimental techniques including neutron scattering and X-ray analysis with supercomputer simulations, ORNL scientists found that water molecules trapped between cellulose fibers are pushed out as the biomass heats up during pretreatment. This loss of water causes the cellulose fibers to move closer together and become more crystalline, making them harder to break down. The team also discovered that lignin and hemicelluloses polymers separate into different phases during pretreatment.

With these findings, the researchers conclude that they need to find a balance which avoids cellulose dehydration but allows phase separation, in order to improve the pretreatment process. But how that could be done still requires further research.