Electrochemical acceleration of chemical weathering for carbon capture and sequestration

Abstract

Abstract We describe an approach to CO 2 capture and storage from the atmosphere that involves enhancing the solubility of CO 2 in the ocean by an engineered process equivalent to the natural silicate weathering process. HCl is electrochemically removed from the ocean and neutralized through reaction with silicate rocks. The alkaline solution resulting from the removal of HCl is neutralized by capturing atmospheric CO 2 and is dissolved into the ocean where the carbon will be stored primarily as HCO 3 − without further acidifying the ocean. On time scales of hundreds of years or longer, some of the additional alkalinity is expected to lead to precipitation or enhanced preservation of CaCO 3 , resulting in the permanent storage of the associated carbon, and the return of an equal amount of carbon to the atmosphere. The overall process is equivalent to the earth’s natural chemical weathering process of silicate rocks. Whereas the natural silicate weathering process is effected primarily by carbonic acid, the engineered process accelerates the weathering kinetics to industrial rates by replacing this weak acid with HCl. In the thermodynamic limit–and with the appropriate silicate rocks–the overall reaction is spontaneous. A range of efficiency scenarios indicates that the process should require 100–400 kJ of work per mol of CO 2 captured and stored for relevant timescales. The process can be powered from stranded energy sources too remote to be useful for the direct needs of populations.