CO fixation by phototrophic microalgae has been addressed as a possible global carbon emissions reducer, whilst simultaneously producing useful products. Especially in Qatar, the prospect of using microalgae for CO abatement is promising: high solar irradiance, large areas of non-arable land, and large amounts of CO emissions make it seemingly the ideal place for algae cultivation. In order to promote high biomass productivities, and subsequent CO uptake rates, effective CO supply to the cultivation system is of high importance. However, the low solubility of CO in water, as well as the limiting tolerance of microalgae to increased CO concentrations, results in low efficiency of CO capture by microalgal production systems. In order to overcome these hurdles, this research focused on selecting local desert microalgae strains with high tolerance to increased CO levels, and developing growth media in order to increase the solubility of CO. Forty-five locally isolated marine microalgae strains were screened for growth under increased CO concentrations, ranging from 0.04% to 30% (v/v). A number of different trends in CO tolerance could be identified from the results; a number of strains showed a clear inhibition of growth with CO concentrations of 5% and higher, whilst others showed increasing growth rates for increasing CO concentrations up to 30%. The trend in growth rate suggests that even higher CO concentration could be applied without growth-limiting effects, and could even stimulate higher growth-rates. In order to further increase the productivity of high CO-tolerant strains, as well as to investigate the effects of pH on the CO tolerance of low-tolerant strains, various strains were cultivated in alkaline media and high CO concentrations. Besides leading to an increased solubility of CO in the culture media, increasing the pH is thought to balance the acidification effect of CO – possibly leading to higher CO tolerances. Overall, applying these strains and media adaptations for large-scale applications is expected to increase the CO transfer efficiency to the culture, resulting in decreased operational costs and higher overall productivities.


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