Renewable & Sustainable Energy Reviews 2017-10-06

A novel strategy for sequestering atmospheric CO2: The use of sealed microalgal cultures located in the open-oceans

Ron G. Smith, Ian J. Smith, Brendan D. Smith

文献索引：10.1016/j.rser.2017.10.001

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摘要

Here we introduce the concept of utilizing microalgal cultures grown in sealed enclosures located in open-oceans to sequester CO2 from both the atmosphere and flue gases. This method of sequestering CO2 overcomes the major limitations of sequestering appreciable CO2 using existing technologies, such as microalgae cultured in open ponds, photobioreactors, or continuous bioreactors on land or near shore. Open ponds require vast surface areas and generally have low net productivity due to light and temperature limitations during the night and winter periods. Continuous algal bioreactors are much more productive, but this comes at the expense of controlling the parameters of the bioreactors, such as light regimes and temperature. The additional energy inputs used to control the parameters of the bioreactors negate their effectiveness of sequestering CO2 on a global scale. Near shore photobioreactors lack the capacity to be scaled up to sequester appreciable CO2. Alternatively, we propose that atmospheric CO2 and/or the flue gases (containing CO2, NOx and SOx) can be collected and transferred to enclosed vessels or bags containing algal cultures situated in the open-oceans. The productivity of the enclosed cultures could be optimized by moving the bags to various locations in the oceans, allowing for control of temperature, irradiance, and hours of daylight. Theoretical calculations using demonstrated CO2 sequestration efficiencies and production rates of microalgal batch cultures suggest that 4 cylindrical enclosures, each with a diameter of 100 m and a depth of 40 m would be able to sequester the CO2 emitted by a 500 MW coal-fired generating plant. On a grander scale, using the same CO2 consumption rates and the enclosures described above, roughly 14,000 enclosures could reduce the CO2 in the troposphere by 1 ppm on a yearly basis, representing half of the total CO2 added to the atmosphere annually.