HYDROTHERMAL PROCESSING OF ALGAE TO PRODUCE COAL AND OIL

The large-scale cultivation of microalgae has the potential to fix significant quantities of carbon dioxide and convert them into lipid-rich biomass, which can in turn be converted into fuels. An energy-efficient process for the recovery of the lipids from the wet algal biomass is critical for the economic and ecological viability of this approach. Hydrothermal carbonization, which involves the heating of the wet algal biomass to around 200°C, results in the formation of a high carbon content, coal-like material, from which over 80% of the initial algal lipids can be recovered by solvent extraction. We have demonstrated this process for several different algal strains and shown that the coal-like material has an energy content similar to bituminous coal, even after solvent extraction of the lipids. In addition to the coal-like solid material, the process also yields an aqueous fraction, which is rich in nitrogen and be can used to recycle this critical nutrient back into the algal cultivation. Beyond the experimental results, this presentation will also provide an overview of hydrothermal processing of wet biomass materials along the temperature continuum from carbonization all the way to gasification.