Thermal processing of biomass is a rapid, low-cost method to produce bio-oil that can be refined to renewable transportation fuels. Major challenges in the utilization of bio-oil for producing biofuels include chemical complexity, acidity and instability. The goal of this work is to simplify biomass thermal product streams to make them more amenable to catalytic upgrading and subsequent use as fuels, optimizing carbon yields.
Dr. Laura Bartley, Associate Professor of Microbiology and Plant Biology, University of Oklahoma (OU) together with Drs. Richard Mallinson and Lance Lobban (Chemical Engineering, OU) and Dr. John Mullet (Biochemistry and Biophysics, Texas A&M University) conducted a study to examine how chemically and physically altering switchgrass and sorghum biomass relates to yields of thermal products under two different temperatute regimes, torrefaction and fast pyrolysis.
This project successfully gathered detailed data on a set of compositionally diverse switchgrass samples and predicted the thermal pyrolysis products of switchgrass and sorghum collections. The team also distinguished among possible associations between composition and products by measuring the thermal products from selectively altered switchgrass biomass, specifically biomass that had been chemically pretreated with water, base, or enzymes and biomass that has been genetically modified to deplete S-lignin and hydroxycinnamates (HCAs) via down-regulation of the phenylpropanoid biosynthesis gene, COMT. Results showed that low S-lignin and low HCA switchgrass releases less methoxyphenols into the torrefaction product stream (Fig.1) but does not reduce overall carbon yields. These results provide new directions for improving thermochemical biofuel production by rendering the torrefaction product stream more acceptable to catalytic upgrading.
Funding of this project was provided by the U.S. Department of Agriculture-National Institute of Food and Agriculture (USDA-NIFA) through the South Central Sun Grant Program.