Chemical Properties of Biocrude Oil from the Hydrothermal Liquefaction of Spirulina Algae, Swine Manure, and Digested Anaerobic Sludge

In an era of water and fuel insecurity, it is important to develop methods to both conserve water and produce fuels from non-petroleum sources. Innovative use of wastewater is part of the solution. Researchers have discovered that it is possible to convert biomass in wastewater to high-value liquid fuels using hydrothermal liquefaction (HTL). Initial biomass chemistry can affect the quality of HTL products, so it is important to test feedstocks prior to large-scale conversion. A group of researchers, including ISTC’s Dr. B.K. Sharma and John Scott, did just that.

They focused on three feedstocks likely to be present in wastewater streams: Spirulina algae, swine manure, and anaerobically digested sludge. The three sources varied substantially in biocrude yields, with sludge yielding 9.4% of the original weight and Spirulina yielding 32.6%. Heating values were similar for all product oils, but, when oils were analyzed more closely, it turned out that their chemistry differed quite a bit depending on the feedstock. Molecular weight, boiling point distribution, and long branched aliphatic content were different for the three feedstocks, underlining the importance of HTL feedstock composition and the need to better understand biocrude chemistry when considering bio-oil uses.