Influence of media composition on the growth rate of Chlorella vulgaris and Scenedesmus acutus utilized for CO₂ mitigation

Atmospheric carbon dioxide levels have increased since the industrial revolution due to the increase in combustion of fossil fuels. These elevated levels of CO₂ have been cited as a significant cause of climate change. Hence, there is a well motivated need to find ways to mitigate CO ₂ emissions. Chemical absorption and geological storage of CO ₂ have high energy consumption, high capital cost and potential leakage. One possible alternative strategy is the use of microalgae for mitigation of CO₂. This paper focuses on the influence of media composition on the growth rate of two microalgae strains, Chlorella vulgaris and Scenedesmus actus. A KNO₃ based medium was found to work better for Chlorella, while a urea based equivalent worked better for Scenedesmus. Upon reduction of the urea concentration, the algae growth rate increased slightly, showing that the urea level was not the limiting ingredient in the medium. The urea based media investigated here resulted in growth similar to that found with previously reported KNO₃ based media. This should result in an economic benefit in large scale algae cultivation for CO₂ mitigation, since urea is typically less expensive than KNO₃. Additional media components were tested and it was found that EDTA and vitamin B do not result in a significant increase in algae growth rate.