Quantifying the intrinsic value of algal biomass based on a multi-product biorefining strategy

Microalgal biomass is poised to become an important feedstock in the quest to decarbonize the fuels and chemical industries. In this way, it is imperative that researchers prioritize efforts for increased chances of economic viability of the microalgae biomass supply chain. This work applies a sequential techno-economic assessment (TEA) methodology to compare the economic trade-offs between microalgae growth and compositional shift while solving for an alternative economic metric: intrinsic algal biomass value, i.e., the revenue obtained from processing and converting the main components of algae biomass - carbohydrates, lipids, and protein - to a portfolio of products. The framework relies on data derived from small-scale cultivations to initially determine the maximum economic potential of different product portfolios as obtained in multiple biorefining setups. The approach further downselects the number of possible strains to undergo an in-depth TEA in order to quantify the value of transitioning from nutrient-replete to nutrient-deplete cultivations. Among the 13 permutations of strains and cultivation strategies analyzed, this study demonstrated an increase in intrinsic biomass value for four strains after the compositional shift: Chlorella sorokiniana DOE1412, Chlorella sorokiniana DOE1116, Scenedesmus obliquus UTEX393, and Scenedesmus obliquus DOE0152.Z. While product selection is critical in the exploitation of microalgal biomass, the four mentioned strains at least double their intrinsic biomass values, reaching up to $264/ton in net margins above minimum biomass selling prices. This is attainable without considering the production of small market size specialty chemicals, instead targeting markets with scalability potential and/or with currently large sizes. Two other strains, namely Picochlorum celeri WT-CSM/EMRE and Tetraselmis striata LANL1001, should have their biomass productivities increased by around 5 g/m2/day in nutrient-deplete cultivations to achieve economic viability. The concept of implementing an objective comparison between different portfolio configurations detailed herein is an innovative approach towards the economic assessment of microalgae valorization strategies.