Carbon Dioxide Removal and Biomass Production from Methane Combustion in the Photobioreactor using Microalgae Spirulina

The aim of this study was to determine the amount of carbon dioxide uptake and biomass production in a photo bioreactor containing Spirulina microalgae as growth medium by injecting the products of natural gas combustion. A photo bioreactor was fabricated and combustion products of natural gas as well as air were injected by separate diffusers. The photo bioreactor was filled by growth medium without carbon source. In the control and test reactors, carbon dioxide was supplied by air and flue gas, respectively. Light source was natural and artificial. Artificial light source was four fluorescent lamps having 10 Klux intensity, which were operated in continuous and intermittent modes. The concentration of carbon dioxide entering in the test reactor was chosen in the range of 580 to 5000 ppm. The concentration of carbon dioxide in the inlet and outlet gas of the reactor was measured by a carbon dioxide detector equipped with NDIR. The algal biomass production and also changes in pH were measured. The flue gas was used as such without any scrubbing or desulfurization. The maximum production of algae using air and combustion products of natural gas having 4100 and 3300 ppm carbon dioxide using artificial intermittent light was 0.07 and 0.2 gL-1 d-1, respectively. Moreover, the maximum concentration of biomass was 0.25 and 1.04 gL-1, respectively. Carbon dioxide biofixation rate was 2.5 and 3.3% in the 3300 and 4100 ppm carbon dioxide runs. Natural gas combustion products can be injected in the photo bioreactor directly and without prior treatment, and it is possible to remove carbon dioxide and produce algae. Biomass productivity with intermittent light was 35% less than continuous light. With the increasing concentration of carbon dioxide in the combustion gas, algal biomass production increased.