Hydrothermal and Solvothermal Approaches for Converting Wet Algal Biomass to Biofuels

Modern society uses liquid and gaseous fuels as energy carriers, so the conversion of biomass in general and algal biomass in particular 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 in several different ways.  This presentation will give an overview of different algal biorefinery options being developed in our lab that employ hydrothermal and/or solvothermal processes.  We will also discuss how these options might be integrated into a sustainable biorefinery.  We will describe recent advances in directly converting wet algal biomass to fuel gases, crude bio-oils, and to crude biodiesel or green diesel fuel.  For example, we have examined and modeled the kinetics of the gasification of algae in supercritical water.  We have also developed two-step processes, both catalyzed and uncatalyzed, for producing biodiesel (using near- or supercritical ethanol) and green diesel (alkanes) from lipid-rich wet algal biomass.  We will also describe recent work on hydrothermal liquefaction of wet algal biomass to produce a crude bio-oil and hydrothermal upgrading of the oil to produce a hydrocarbon fuel.  The processes noted above will be used to illustrate the usefulness of solvothermal and hydrothermal methods for processing wet algal biomass.  The fluids employed (water or ethanol) serve not only as the solvent but also as a key reactant in the process.