Supercomputing Improves Biomass Fuel Conversion

by Holly Ober (Univesity of California Riverside News) Researchers combine supercomputing with nano-imaging to reveal how to efficiently break down plant biomass and transform it into transportation fuels -- ... In order to access the energy-rich sugars found in the plant cell walls, researchers have renewed focus on solvating lignin, a complex polymer also found in plant cell walls that acts as a natural shield, blocking both chemical and biological attack. Lignin is particularly effective in preventing commercial enzymes from digesting cellulose, which makes up the bulk of sugars found in biomass.

In the past, different specialized chemicals and pretreatment methods have been used to improve enzyme access to cellulose but were ineffective at removing lignin. The use of strong acids, ionic liquids, ammonia, and sulfite treatments have somewhat improved the digestibility of cellulose, but these methods also leave lignin behind, making cellulose expensive to recover. Other methods have applied co-solvents such as ethanol and acetone solvate to remove lignin, but they require very high reaction temperatures that also cause the remaining sugars to degrade.

As a result, economically viable methods of transforming biomass into biofuels have yet to be realized.

Charles Cai, an assistant research engineer at the Center for Environmental Research and Technology in the Marlan and Rosemary Bourns College of Engineering at UC Riverside, and Abhishek S. Patri, a doctoral student in chemical and environmental engineering, led a team of researchers taking a new direction to focus on identifying highly specialized co-solvents, substances added to a primary solvent to make it more effective, that can facilitate milder temperature solvation and release of lignin from the plant cell walls. This is known as a “lignin-first” approach to breaking down biomass.

The UC Riverside researchers enlisted the research team at Oak Ridge National Laboratory’s Center of Molecular Biophysics, led by Jeremy Smith, to help construct a 1.5 million atom molecular simulation to reveal how the co-solvent pair consisting of tetrahydrofuran, or THF, and water are particularly effective at altering the interactions between lignin and cellulose, helping to drive multiple key mechanisms responsible for breaking down biomass.

By putting lignin first, highly functional co-solvents can help to integrate multiple processing steps while allowing both lignin and sugars to be easily recovered as valuable chemical building blocks, making renewable fuel production easier and more cost-effective. The research team hopes that by revealing the synergistic mechanisms of biomass breakdown by co-solvents THF and water, they can inspire others to identify additional multifunctional co-solvent pairs.