Fuels from Biomass via Supercritical Fluid Processes
University of Michigan
Wednesday, May 11, 2009 10:00am
Ben Bandy Conference Center
Center for Applied Energy Research
Biomass, whether energy crops or residues from agriculture, is a renewable source of energy. Modern society uses liquid and gaseous fuels as energy carriers, so biomass conversion to these fuels is an integral part of a sustainable energy future. Solvothermal processes, which involve the simultaneous action of a solvent and elevated temperature, perhaps along with a catalyst, can do this necessary conversion. This lecture will describe our recent work in converting biomass to gases and bio-oils to liquid diesel fuel. We examined the gasification of biomass in supercritical water and the esterification of oleic acid in supercritical ethanol. Cellulose and lignin were converted to gases rich in H2 and CH4. Both the gas yield and its composition were sensitive to changes in the gasification temperature, the biomass loading, and the water density.
Additionally, metal catalysts can be used to obtain further control of the rate and selectivity of the gasification reaction. Esterification of free fatty acids by alcohols is one step in an envisioned catalyst-free process for biodiesel production from triglycerides. The esterification proceeded smoothly in supercritical ethanol, and we examined the effects of the process variables on the kinetics and ester yields. The processes noted above are but two that illustrate the usefulness of supercritical fluids for biomass processing. In both of these systems, the fluid (water or ethanol) serves not only as the solvent but also as a key reactant in the process.