Influence of biodiversity, biochemical composition, and species identity on the quality of biomass and biocrude oil produced via hydrothermal liquefaction

We compared several measures of quality for biomass and biocrude oil produced via hydrothermal liquefaction for monocultures and polycultures of the freshwater microalgae Ankistrodesmus falcatus, Chlorella sorokiniana, Pediastrum duplex, Scenedesmus acuminatus, Scenedesmus ecornis, and Selenastrum capricornutum. On average, the 2-species cultures provided product quality comparable to that of the monocultures, while that of the average 4- and 6-species polycultures was lower. No single monoculture or polyculture performed the best with respect to all quality metrics considered, including biomass fatty acid content and biocrude elemental content and higher heating value. However, for each measure of quality, some polycultures did outperform or match the performance of the best monoculture for each respective metric. Numerous polycultures performed outside the range of product quality exhibited by their constituent species (transgressive overyielding), and polycultures with P. duplex did so to the greatest extent. Microalgal biochemical composition was correlated with biocrude properties, however including species identity as an additional correlation variable further explained the observed variation. Finally, we highlight several polycultures that offer potentially compelling trade-offs between product quantity and quality compared to the most productive monoculture.