Comparison of net energy potential between bio-ethanol and lipid extraction derived from Chlorella vulgaris

Abstract

Proper implementation of sustainable energy sources in developing countries could decrease their dependence on natural gas, oil, and investments in renewable energy technologies would be more cost effective than fossil fuels. The first and second bio fuel generation biomasses have been used as a feedstock to produce biofuels, which cannot satisfy the worldwide demand. Therefore, as the third biofuel generation, algae are viewed as a promising feedstock for the production of various kinds of biofuels such as bio-ethanol, biodiesel, and lipid. There were very few researches related to the energy comparison of biofuel production from microalgae. Therefore, this research was conducted to compare the net energy potential between bio ethanol and lipid extraction derived from Chlorella vulgaris. For this comparison, Chlorella vulgaris was cultivated in photo-bioreactor using Bold’s basal medium and harvested by sedimentation and centrifugation at 4500 g for 10 minutes. Initially, five grams of the same amount of biomass was used for the production of bio-ethanol and extraction of lipid. Bio ethanol was prepared using alkaline pre-treatment method under 0.75 % of NaOH (w/v) and heated at 120 oC for 30 minutes. Yeast was cultured in LB medium and used to ferment the pre treated microalgae in the incubator for 96 hours at 30 °C at 200 rpm. From the same amount of five grams of microalgae, lipid was extracted by bligh and dyer method with the usage of Chloroform: methanol at 2:1 ratio. Five grams of microalgae produced 0.25 g of bio-ethanol (5 %) and 0.33 g of lipid (6.6%). Considering the energy input given for each procedure, the net energy value of bio-ethanol significantly higher than the lipid extraction. Therefore, the lipid extraction should be considered as an effective method compared to bio-ethanol production from chlorella vulgaris.