AN EVALUATION OF AUTOTROPHIC MICROBES FOR THE REMOVAL OF CARBON-DIOXIDE FROM COMBUSTION GAS STREAMS

Carbon dioxide is a greenhouse gas that is believed to be a major contributor to global warming. Studies have shown that significant amounts of CO2 are released into the atmosphere as a result of fossil fuels combustion. Therefore, considerable interest exists in effective and economical technologies for the removal of CO2 from fossil fuel combustion gas streams. This work evaluated the use of autotrophic microbes for the removal of CO2 from coal fired power plant combustion gas streams. The CO2 removal rates of the following autotrophic microbes were determined: Chlorella pyrenoidosa, Euglena gracilis, Thiobacillus ferrooxidans, Aphanocapsa delicatissima, Isochrysis galbana, Phaodactylum tricornutum, Navicula tripunctata schizonemoids, Gomphonema parvulum, Surirella ovata ovata, and four algal consortia. Of those tested, Chlorella pyrenzoidosa exhibited the highest removal rate with 2.6 g CO, per day per g dry weight of biomass being removed under optimized conditions. Extrapolation of these data indicated that to remove CO2 from the combustion gases of a coal fired power plant burning 2.4 x 10(4) metric tons of coal per day would require a bioreactor 386 km(2) x 1 m deep and would result in the production of 2.13 x 10(5) metric tons (wet weight) of biomass per day. Based on these calculations, it was concluded that autotrophic CO2 removal would not be feasible at most locations, and as a result, alternate technologies for CO2 removal should be explored.