(38c) Hydrothermal Liquefaction of Wild-Harvested Cyanobacteria from a Hypereutrophic Lake in Wisconsin

Processing by hydrothermal liquefaction (HTL) of wild-harvested cyanobacteria could have the potential to provide a sustainable, domestic fuel supply and nutrients for use in agriculture while removing a source of hypoxia from over-burdened waterways. Lab-scale cultured strains of microalgae has shown freshwater cyanobacteria as a promising feedstock with low ash content, leading to high biocrude yields. However, HTL of wild-harvested microalgal strains has yet to be fully investigated. Additionally, the intermittent nature of cyanobacteria blooms raises questions about the need to store harvested microalgae and the effect of storage time on the products.

Wild-harvested microalgae sampled from Lake Tainter, a hypereutrophic lake in Northwest Wisconsin, was collected and prepared in two ways: dried while fresh and stored long-term, and stored wet long term then dried before HTL processing. Fractions of the feedstock, mostly consisting of Microcystis Aeruginosa, were treated via HTL at a range of temperatures (280-300°C), solid loading ratios (10-25% w/w), and reaction holding times (30-60 min) in 30 mL batch reactors. The percent yield of the products and chemical composition of the biocrude and aqueous fraction (PHWW) was characterized by GC-MS, ICP-MS, and elemental analyzer.