Models for microalgae hydrothermal liquefaction were developed from conversion of Nannochloropsis cultivated to varying biochemical composition and fatty acid content.

A multiphase component additivity (MCA) model to quantitatively predict both yields and characteristics of products from hydrothermal liquefaction of microalgae.

Modeling efforts to understand the financial implications of microalgal biofuels often assume a static basis for microalgae biomass composition and cost, which has constrained cultivation and downstream conversion process design and limited in-depth understanding of their interdependencies. For this work, a dynamic biological cultivation model was integrated with thermo-chemical/biological unit process models for downstream biorefineries to increase modeling fidelity, to provide mechanistic links among unit operations, and to quantify minimum product selling prices of biofuels via techno-economic analysis. Variability in design, cultivation, and conversion parameters were characterized through Monte Carlo simulation, and sensitivity analyses were conducted to identify key cost and fuel yield drivers. Cultivating biomass to achieve the minimum biomass selling price or to achieve maximum lipid content were shown to lead to suboptimal fuel production costs. Depending on biomass composition, both hydrothermal liquefaction and a biochemical fractionation process (combined algal processing) were shown to have advantageous minimum product selling prices, which supports continued investment in multiple conversion pathways. Ultimately, this work demonstrates a clear need to leverage integrated modeling platforms to advance microalgae biofuel systems as a whole, and specific recommendations are made for the prioritization of research and development pathways to achieve economical biofuel production from microalgae.

As an effort to develop affordable and sustainable energy sources, algae-derived biofuels have attracted considerable interest. As use of individual conversion processes targeting a subset of biochemical components (e.g., extraction and upgrading of lipids) has been shown to be economically unfeasible, there is a recognized need for integrated conversion systems that can valorize algal feedstocks with varying cell compositions. In this study, two hybrid systems (HBD-1, HBD-2) are proposed to enable more efficient conversion of all biomass components (lipids, proteins, carbohydrates) by leveraging two complementary systems: direct hydrothermal liquefaction (DHTL) and combined algal processing (CAP). Demonstrative experiments with Scenedesmus acutus show a 12.2−34.3% increase in fuel yields relative to individual systems (DHTL, CAP). Subsequent modeling efforts reveal substantial improvements stemming from CAP valorization of carbohydrates and lipids and DHTL valorization of proteins and CAP residuals. The maximum biomass-to-fuel conversion efficiencies for lipids/proteins/ carbohydrate cell components are 79%/34%/75% (HBD-2), and techno-economic analysis suggests a 3.2−62.1% reduction in minimum fuel selling prices (MFSPs). The increased fuel yields and reduced MFSPs highlight the flexibility of the hybrid systems for biofuel production, revealing advantages of these systems for broader ranges of feedstocks, including ones not traditionally considered for fuel production.

Diverse sources of wastewater organic carbon can be microbially funneled into biopolymers like polyhydroxybutyrate (PHB) that can be further valorized by conversion to hydrocarbon fuels and industrial chemicals. We report...