Influence of thermal behavior and nutrient sources on microalgal biomass for fuel use

Suchitra Rakesh, Subburamu Karthikeyan and Dolly WattalDhar

Third generation biofuel i.e., microalgal biofuel production is considered as the most favorable biofuel source as it is non-toxic, biodegradable and renewable. The lipid content of microalgae is 30-100 times more than that of oilseed crops. The growth response of Tetradesmus wisconsinens is and Botryococcus sp. were studied under varying concentrations of carbon dioxide, salinity, light intensity, photoperiod, nitrogen, carbon, and phosphorus sources. Higher biomass for Botryococcus sp. and Tetradesmus wisconsinensis was obtained at 1% and 0.036% carbon dioxide concentrations respectively. Sodium bicarbonate, when provided as carbon source, yielded a specific growth rate of 0.039 g L-1 and 0.044 g L-1 for Botryococcus sp. and Tetradesmus wisconsinensis respectively. As regard to nitrogen source, sodium nitrate was found to be enhancing the biomass of both the algae, while phosphorus nutrition was not influencing the specific growth rate. The studies on the influence of salinity on microalgal isolates revealed that Botryococcus sp. grew better under control compared to various NaCl concentrations tested. Tetradesmus wisconsinens is recorded maximum growth at 30 mMNaCl concentration. The algae produced higher algal biomass on a dry weight basis at 14:10 (light/dark) photoperiod cycles with an irradiance of 62.64 µ mol m-2s-1. Pyrolytic studies confirm the final weight loss of 42-56% under inert atmosphere from 200-800⁰C at a heating rate of 40°C min-1. The present study could be used for checking the biodiesel potential of microalgal strains and hence can be taken for pilot scale production.

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