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.
