Carbon Sequestering: Capturing Carbon with Chemistry

Looking for a way to remove carbon from gas?  Professor Arun Majumdar and colleagues at UC Berkeley want use carbonates as a way to capture CO2.  The chemistry of CO2 is critical in the formation of carbonates.  The dissolution of CO2 in water can be increased with pressure.  However, it is kinetically impractical for technological applications of CO2 capture.  Therefore a catalyst is needed to reduce the barrier and speed up the reaction.


Fortunately, such a catalyst does exist in the biological world, and it is a protein enzyme called carbonic anhydrase1 (CA).  CA is used for both photosynthesis in plants and maintaining blood pH in animals.  It is one of the most efficient enzymes found in nature.  Furthermore, it could be synthesized in large quantities using genetically engineered organisms.


As part of this project, we will develop a testbed reactor system called “The Carbonator,” as shown in the diagram below.  Such a system will utilize CA to convert CO2 into (bi)carbonates in a rapid and efficient manner.  Such a system will also allow us to answer some fundamental questions that need to be addressed to make it a practical solution for CO2 capture and storage.  The answers obtained from “The Carbonator” will form the basis for developing accurate engineering and economic models for scaled up versions of this process.  Preliminary calculations have suggested that when scaled up, the cost of enzyme may not be as expensive as the energy cost of pumping water.


With regards to the fate of (bi)carbonates, the best option is to transport and inject the dilute acidic bicarbonate/carbonate solution deep inside alkaline rock formation so that when it flows through the rock, it will be neutralized.  This seems much more cost-effective and environmentally benign than breaking the rocks in open quarries and transporting them to power plants, which is known to be expensive.  Furthermore, it is has been well studied that the volume of alkaline rock formations near the earth’s surface is more than enough to absorb all the CO2 that can ever be produced by burning all of the world’s fossil fuel reserves.


Next Step: Develop the Cabonator testbed reactor system in order to convert CO2 into (bi)carbonates in a rapid and efficient manner.