Growth, lipid extraction and thermal degradation of the microalga Chlorella vulgaris

The microalga Chlorella vulgaris was cultured in a combined medium obtained by mixing standard Jaworski medium with a solution from the modified Solvay process that contained only NaHCO 3 and NH 4 Cl. Cell number, pH and nitrogen content were monitored throughout growth. Lipids were extracted from lyophilised biomass using CHCl 3 –MeOH. A combination of grinding, microwave treatment and sonication proved to give the best lipid extract yield. Freeze-dried algal biomass was also utilised for thermal degradation studies. The degradation exhibited three distinct regions – primary cell structure breakage paralleled by evaporation of water, followed by two predominant exothermic degradation processes. The latter were modelled using n th order apparent kinetics. The activation energies of the degradation processes were determined to be 120–126 kJ/mol and 122–132 kJ/mol, respectively. The degradation model may be readily applied to an assortment of thermal algal processes, especially those relating to renewable energy.