Removing Roadblocks to Make the Conversion of CO2 Emissions to Diesel and Jet Fuel Using Algae an Industrially Viable Process

Algae-based carbon capture represents one possible solution to the issue of rising greenhouse gas levels. In addition to capturing CO₂ emissions, this approach facilitates CO₂ conversion to algal biomass, the components of which â?? including algal lipids â?? can be monetized. However, the overall efficiency and economic constraints of extracting, purifying and upgrading algal lipids present challenges that must be overcome for algae oil to become a viable source of fuels and chemicals. The work described in this contribution includes the optimization of algal lipid extraction and purification processes designed to avoid the destruction of valuable algae components and the use of an improved catalytic approach to obtain drop-in hydrocarbon fuels from the purified algal lipids. Low-cost, scalable methods are employed, including the direct transesterification of wet algae biomass to extract algal lipids and the use of low-cost adsorbents to purify the crude algal lipids. Raw algae, as well as crude and purified algal lipids, were analyzed throughout in order to observe the evolution of the lipid profile and the elemental composition of the feed as it was processed. Similarly, the spent adsorbents and catalysts used during the purification and upgrading of the algal lipids were analyzed as a means to gain insights into the final destiny of metals and heteroatoms undesirable for fuel applications. Activated carbon was found to be an affective adsorbent for the elimination of impurities such as chlorophyll, phospholipids and sterols from the crude algae oil. Notably, comparison of the UV-Vis spectra of a chlorophyll standard, the crude algal lipids and the purified algal lipids showed a complete absence of chlorophyll in the purified sample. Moreover, analysis of the purified lipids and the product of their catalytic upgrading revealed the latter to be ideal for transportation fuel (diesel and jet-fuel) applications.