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.
