Multi-Scale Analysis of Lignin for Drop-In Biofuels: From Life-Cycle Assessment of Feed-Stocks to Quantum Chemical Analysis of Pretreatment Methods

Lignocellulosic feedstocks such as corn stems and husks (stover) and wood are comprised of three types of complex polymers: cellulose, hemicellulose and lignin. Of these three, only cellulose is generally converted to biofuels, with some methods also incorporating hemicellulose. Lignin is the most difficult of the three to process and convert, and is generally burned to produce electricity rather then converted to biofuels, even though it contains up to 40% of the available energy. Tapping into this unused fraction would be a significant step toward sustainability in the transportation sector. Ideally, the final product of biomass conversion would be gasoline and jet fuel which could be used without restructuring of transportation infrastructure (so called “drop-in” fuels). Virent, a biofuel startup in Madison, WI, has developed such a process beyond the pilot phase, but currently only uses cellulose and hemicellulose derivatives as feedstocks. In order to access the energy available in lignin, an effective method for processing it into viable hydrocarbons is needed. Once such a method has been devised and greenhouse gas (GHG) emissions associated with this process can be calculated, we can address the question of whether converting lignin to biofuel is the best way to reduce GHG. It is possible that under certain circumstances, simply burning lignin for electricity (thus reducing the need for other sources of electricity) may reduce total GHG emissions more than converting it to biofuel. To this end, the goals for this proposal are to: � Investigate the breakdown of lignin under acidic conditions at the detailed mechanistic level using quantum chemical calculations on lignin model compounds and microkinetic analysis of the reaction networks. This work will be carried out in collaboration with the Host Mentor, Professor Linda Broadbelt at Northwestern University, and the Partner Mentor, Dr. Randy Cortright, founder and Chief Technology Officer at Virent. Though small sets of calculations have previously been performed, the task of investigating the breakdown of this complex polymer requires a systematic investigation. Our calculations coupled with microkinetic analysis will provide an entirely new level of understanding of the degradation process.