PERFORMANCE EVALUATION OF PHOTOBIOREACTOR FOR MICROALGAE CULTIVATION AND ITS CODIGESTION FOR BIOGAS PRODUCTION

Abstract

Pakistan, being an under-developed country faces significant challenges in its energy sector with new power plant being constructed to address this issue. But the usage of fossil fuel in power plants is contributing to a significant emission of GHG gases into the atmosphere, specifically Carbon Dioxide (CO2). The release of CO2 is accelerating global warming and climate change that is adversely affecting the world-wide economic stability and social aspects. To mitigate these effects, research is being conducted to develop new solutions. One such solution lies through the intersection of technology and biology named algal Photobioreactor (PBR). The microalgae have extraordinary capabilities to sequester carbon dioxide (CO2) in their cells. In this project, Scenedesmus sp was cultivated in bubble column type Photobioreactor supplied initially with 10% v/v CO2 to replicate industrial flue gas concentration with supply period of 5 minutes at a flow rate of 5 L/min, 7 L/min, and 9 L/min. The flow rate of 5 L/min resulted in a significant increase in algal concentration by 305 mg/L in a few hours with the highest CO2 fixation rate of 51.6 mg/L-hr. After harvesting from the PBR, the algae was co-digested with banana peels using cow manure as inoculum in an anaerobic digestor for biogas production. Cumulative production of biogas was 288 L/kgVS after just 21 days. The results of the study concluded that microalgae is a sustainable solution to sequester the CO2 emitted from flue gas, mitigate its effect towards climate change, and be co-digested with suitable low nitrogen substrate as source of clean, green energy.