Discharge of process water into tailings ponds is associated with many mining operations, including that of bitumen.. These tailings ponds can be used to grow organisms, such as algae, which, in turn, fix CO2 and degrade unwanted dissolved components. After processing, algae can be used for the production of fuels (for example, biodiesel or methane). In this work, we explored the potential for growth of a unicellular algae, Chlorella pyrenoidosa, in tailings water from an oil sands mining and upgrading operation. Once we determined that it was possible to grow algae in the tailings water, we designed and optimized minimal growth media for biomass (algae) production and did a preliminary engineering estimate of the potential for CO2 fixation. The medium components required for growth of C. pyrenoidosa in 95% oil sands tailings water (OSTW) were screened using a two-level full factorial experiment. Sodium nitrate, phosphate, and Fe-ethylenediaminetetraacetic acid (EDTA) were the most important medium components. After this work, response surface methodology (RSM) was used to find the optimum concentrations of these nutrients. The optimum concentrations of sodium nitrate, phosphate, Fe-EDTA, and trace metal solution were 11.9 mM, 9.4 mM, 49.5 mu M and 2 mL/L, respectively. On the basis of an optimized specific growth rate of 0.085 g L-1 day(-1), it was estimated that 12 million tons/year of CO2 could be fixed by C. pyrenoidosa growing in the tailings ponds in the Athabasca region of Canada. This value has to be considered optimistic because of fluctuations in temperature, light, and other growing conditions, which would be experienced in the full-scale system.