Green biomass processing to lower slurry viscosity and reduce biofuel cost
C. Luke Williams, Mikael Karlsson, Rachel Emerson, William A. Smith, Tiasha Bhattacharjee
Abstract
Sustainable fuels for industries that cannot be easily electrified, like aviation and marine, will be crucial to achieving a carbon neutral economy. Processing wet solids through a process like hydrothermal liquifaction to produce upgradeable bio-oil is one pathway that could transform high moisture waste into a fuel. This work pioneers two green processing pathways to produce a biomass feedstock for liquefaction that is far less viscous at higher solids loadings than traditional slurries. This decrease in viscosity could significantly improve the profitability of producing fuels through slurry-based conversion processes. Natural biological degradation of corn stover before grinding has been shown to lower slurry viscosity by a factor of three and torrefaction has been shown to produce slurries that are 150x less viscous than the original material. Additionally, new insight has been gained into the critical physical and chemical parameters that impact slurry viscosity. Common parameters in slurry processing, like the average particle size, shear rate, and solids loadings clearly control viscosity, and these results are confirmed for biomass. Additionally, new physical parameters like aspect ratio and sphericity, as well as chemical parameters like extractives content, non-structural sugars, and zeta potential have been shown to impact and be good predictors of slurry viscosity and processability.