Biolubricant Synthesis by Additization and Chemical Modification from Lipid-Rich Brackish Coelastrella sp. Using a Biorefinery Approach

Abstract

With a sizable market share and widespread use in automotive and industrial applications, biolubricants are produced from the oils of terrestrial plants that have undergone chemical modification or additive addition. Brackish or marine microalgae utilize less arable land and have a lower freshwater footprint compared to terrestrial plants. They are thus a potential source of raw materials for the production of biolubricants. This study screened eight marine microalgae, i.e., Coelastrella sp., Chlorocystis sp., Ceatocerous sp., Neochloris sp., Picochlorum sp., Tisochrysis sp., Tetraselmis sp., and Synechococcus sp. for their lipid and pigment content as a preliminary step. Coelastrella sp., Tetraselmis sp., and Chlorocystis sp. were chosen for additional study in outdoor cultivation based on total lipid, pigments, and harvestability. Coelastrella, Tetraselmis, and Chlorocystis species had total lipid contents of 50.2, 7.6, and 9.1% (w/w), respectively. In Coelastrella sp., total carotenoids, monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and saturated fatty acid (SFA) concentrations were 0.3, 45.8, and 51%, respectively. Based on total carotenoids, polyunsaturated fatty acid, and lipid content, Coelastrella sp. was chosen to produce biolubricants by chemical modification and addition of its lipid. Kinematic viscosities and the viscosity index of the EVA-added Coelastrella sp. biolubricant were higher than those of the chemically produced Coelastrella TMP triesters. The thermal stability of the Coelastrella biolubricant with EVA additive was higher, whereas chemically synthesized TMP triester biolubricant had considerably lower thermal stability. A 1% increase in EVA reduced the coefficient of friction of SFA biolubricant from 0.075 to 0.03 and the wear rate from 12 μ gm N–1 m–1 to 0.6 μ gm N–1 m–1, resulting in 60% and 95% reduction in friction and wear rate, respectively, making it a potential lubricant basestock for a variety of industrial applications.