Chlorella vulgaris as a green biofuel factory: Comparison between biodiesel, biogas and combustible biomass production.

Biofuels are viewed as the answer to safeguard the currently challenged energy security. To this end, the present study provides a comparison between approaches regarding microalgal biomass conversion to bioenergy, with a view on sustainable implementation. The energetic valorization of Chlorella vulgaris biomass cultivated under heterotrophic, sulfur-limited conditions was investigated through the biofuels biodiesel, biogas (biomethane) and combustible dry biomass. The lipid productivity can reach the value of 442.9 ± 6.5 mg L-1 d-1 containing suitable fatty acids for biodiesel production. Next, biochemical methane potential (BMP) assays yielded 360.9 ± 20.2 mL CH4 g VS-1added under mesophilic conditions, while the calorific value of dry C. vulgaris biomass was measured as 24,538 ± 182 kJ kgDW-1 (5,865 ± 43 kcal kgDW-1). Considering the downstream processing required in each approach, the most promising energy valorization method is anaerobic digestion able to reach values up to 20,862 kJ Lreactor-1 day-1 in continuous systems.