Abstract
BackgroundMicroalgae possess numerous advantages for use as a feedstock in producing renewable fuels and products, with techno-economic analysis (TEA) frequently used to highlight the economic potential and technical challenges of utilizing this biomass in a biorefinery context. However, many historical TEA studies have focused on the conversion of biomass with elevated levels of carbohydrates and lipids and lower levels of protein, incurring substantial burdens on the ability to achieve high cultivation productivity rates relative to nutrient-replete, high-protein biomass. Given a strong dependence of algal biomass production costs on cultivation productivity, further TEA assessment is needed to understand the economic potential for utilizing potentially lower-cost but lower-quality, high-protein microalgae for biorefinery conversion.ResultsIn this work, we conduct rigorous TEA modeling to assess the economic viability of two conceptual technology pathways for processing proteinaceous algae into a suite of fuels and products. One approach, termed mild oxidative treatment and upgrading (MOTU), makes use of a series of thermo-catalytic operations to upgrade solubilized proteins and carbohydrates to hydrocarbon fuels, while another alternative focuses on the biological conversion of those substrates to oxygenated fuels in the form of mixed alcohols (MA). Both pathways rely on the production of polyurethanes from unsaturated fatty acids and valorization of unconverted solids for use as a material for synthesizing bioplastics. The assessment found similar, albeit slightly higher fuel yields and lower costs for the MA pathway, translating to a residual solids selling price of $899/ton for MA versus $1033/ton for MOTU as would be required to support a $2.50/gallon gasoline equivalent (GGE) fuel selling price. A variation of the MA pathway including subsequent upgrading of the mixed alcohols to hydrocarbon fuels (MAU) reflected a required solids selling price of $975/ton.ConclusionThe slight advantages observed for the MA pathway are partially attributed to a boundary that stops at oxygenated fuels versus fungible drop-in hydrocarbon fuels through a more complex MOTU configuration, with more comparable results obtained for the MAU scenario. In either case, it was shown that an integrated algal biorefinery can be economical through optimal strategies to utilize and valorize all fractions of the biomass.
Highlights
Microalgae possess numerous advantages for use as a feedstock in producing renewable fuels and products, with techno-economic analysis (TEA) frequently used to highlight the economic potential and techni‐ cal challenges of utilizing this biomass in a biorefinery context
The two pathways share a number of commonalities, with the main difference being that the mild oxidative treatment and upgrading (MOTU) pathway follows a more complex thermochemical upgrading strategy to produce hydrocarbon fuels while the mixed alcohols (MA) pathway involves a more simplistic biological approach with less processing, albeit producing oxygenated fuels
The MA pathway demonstrated moderate economic benefits compared to the MOTU pathway, highlighting potential advantages if such oxygenated molecules can be effectively implemented into the fuel market at the same price point as that of hydrocarbon fuels, and/or blended as at low levels into the hydrocarbon fuel pool
Summary
Microalgae possess numerous advantages for use as a feedstock in producing renewable fuels and products, with techno-economic analysis (TEA) frequently used to highlight the economic potential and techni‐ cal challenges of utilizing this biomass in a biorefinery context. The establishment of a global-scale biobased economy will create a need for novel feedstocks and processes aiming at the supply of fuels and products. From this standpoint, microalgae production and conversion in integrated units may play a significant role in this network. The possibility of maximizing biomass value through the extraction of very high added value products is often limited by species, cultivation strategy, and other factors [3], as well as by their market size, which hinders the application of this strategy in a scenario of multiple commodity fuel-scale plants. The premise, changes for commodity chemicals and other compounds with otherwise substantial market sizes given a more elastic demand
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