Temperature and nutrient coupled stress on microalgal neutral lipids for low‐carbon fuels production

Abstract

A freshwater Chlorella sp. was cultured at temperatures from 10 to 45 °C and synergistic stress was employed by using selective and complete nutrient depleted growth media. Temperature fluctuations were found to have a significant effect on the microalgae physiology. The optimum temperature of 35 °C shows suitability for growth in a sub‐tropical climate. The fatty acid methyl esters’ (FAMEs') composition was significantly altered when cultures were incubated under various pre‐determined stress conditions. The effect of dual stress was found to have the greatest increase in the lipid yield, averaging 55% (w/w). The majority of the identified FAMEs (C16 and C18) showed the potential for quality biodiesel and aviation fuel due to the characteristics of FAME. This study is relevant for commercial‐scale biodiesel production and the technologies developed would improve the economic feasibility and potential of microalgal biomass feedstock for biodiesel production by transesterification. There is also high potential for low‐carbon jet fuel by thermal cracking or pyrolysis and fractionation of crude‐bio‐oil from Chlorella sp. These processes will convert carbon chains or FAMES in the C14 to C16 range, which is appropriate for low‐carbon jet fuel. It is therefore possible to generate biodiesel and aviation fuel from Chlorella sp. cultivated in freshwater at achievable temperatures in a sub‐tropical environment under total nutrient deprivation, aiming to stimulate a bio‐oil increase. © 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd.