Ultrahigh-resolution mass spectrometry lipidomics fingerprinting of extracted algae oils guides hydroprocessing needs for sustainable aviation fuels

Abstract: The global demand for sustainable aviation fuel (SAF) is predicted to increase from 23 billion liters per year in 2030 to 450 billion liters per year in 2050. Multiple carbon feedstocks will be required to hit these targets, and algae is an attractive feedstock due to its rapid growth, production capabilities in arid environments, its use for waste cleanup, and its ability to capture carbon from industrial processes as well as the environment. Currently there is an approved pathway from fats, oils, and greases (FOGs) to SAF through hydroprocessing, which may also lend itself to algae-derived lipids and oils. However, there is currently little information about the chemical composition of industrially relevant oils extracted from algae and how they compare to FOGs. The work presented here, reveals that chemical pretreatment to increase oil yield may also affect the chemical composition of oils extracted from algae. Oils were generated with dilute sulfuric acid pretreatment of algae prior to extraction. Analysis was conducted for nine algae biomass sources, including wastewater-derived algae. Results from fatty acid methyl ester (FAME) and lipidomics analysis revealed less than 60% mass closure for most oils based on traditional lipid composition. However, utilization of ultrahigh resolution mass spectrometry provides the ability to determine chemical formulas for unknown components to determine likely composition of unidentified lipid derivatives. These components were shown to be highly dependent on the algae strain. A large number of complex N-containing lipid constituents were identified and point to specific nitrogen removal requirements, either prior to or during hydroprocessing. This technique provides key insights into the composition of algae-derived oils and associated quality metrics that is essential to understanding the viability of upgrading to SAF through the existing hydroprocessing pathway.