Growth of Scenedesmus obliquus under artificial flue gas with a high sulphur concentration neutralized with oil shale ash

摘要

Oil shale is the main energy resource in Estonia, which generates large amounts of CO2 and waste oil shale ash. Flue gas from oil shale combustion can also contain large amounts of SO2. Microalgae can be used for biological sequestration of carbon from flue gas. In this research, green algae Scenedesmus obliquus were grown with 14% CO2 in 1 L bioreactors. Sulphuric acid was added with a concentration of 500 ppm and 1000 ppm in order to imitate the dissolution of sulphur dioxide from flue gas into the growth medium. Oil shale ash was used to neutralize SO2. Biomass measurements of S. obliquus, carried out every 24 hours for 7 days, were used as a proxy for carbon fixation. The biomass yields of the untreated control and of the treatments were similar (maximum yield 2.9, 3.1, and 3.9 g La€“1 for the control, 500 ppm, and 1000 ppm treatment, respectively), suggesting that neither the sulphur nor the ash had an inhibitory effect on algal growth. In fact, the biomass yield was slightly higher in the treatments, which implies that minerals contained in waste ash could be utilized by algae. The calculated CO2 fixation rate was 0.45 g La?’1 da?’1 for the control, and 0.62 and 0.83 g La?’1 da?’1 for 500 ppm and 1000 ppm treatment, respectively. Therefore, microalgae can be used for carbon sequestration from flue gas. Further research should be done in order to optimize the growth conditions and maximize carbon fixation.