Extractable liquid, its energy and hydrocarbon content in the green alga Botryococcus braunii

Due to sparse sampling across races, studies on various strains of Botryococcus braunii have effectively been indiscriminate, and so the target strains for energy production have not come clearly into focus. This study compares extractable liquid biofuel content, bioenergy content and hydrocarbon content across 16 strains B. braunii (A, B and L races) by direct combustion of algal biomass using thermogravimetric analysis (TGA), pressure differential scanning calorimetry (PDSC) and gas chromatography/mass spectrometry (GC/MS). All B. braunii strains were cultured in the same environmental conditions in 250 ml flasks, and were harvested for analysis when algae reached the exponential growth phase. Significant differences were detected within and between races A, B and L. The ranges of variation in extractable liquid, biofuel energy and hydrocarbon contents in algal dry biomass were 10–40%, 10–60% and 4–25%, respectively. The race B strains (Ayame 1, Kossou 4, Overjuyo 3 and Paquemar) had more than 21% of dry weight comprising C31-C36 hydrocarbons, which are suitable for biofuel and bioenergy production. The Overjuyo 7 and CCAP 807/2 strains in race A and the Madras 3 and Yamoussoukro 4 strains in race L also showed high biofuel production with extractable liquid biofuel accounting for >30% of dry weight. This study identified particular B. braunii strains that are suitable for biofuel production. The application of TGA and PDSC provides a useful analytical approach for assessing the biodiesel production potential of microalgae.