A conceptual multi-step process demonstrates the feasibility of CO2 sequestration in an integrated operation utilizing by products primarily obtained from fossil fuel combustion (fly ash) and oil and gas production (brine). This process includes a carbonation reaction utilizing a brine solution and CO2 as reactants under mild reaction conditions. CaO rich fly ashes are added to increase the pH level of the reactant brine, maximizing the reaction efficiency of the carbonation reaction. Furthermore, these materials can also provide a source of Ca in addition to the Ca present in the brine for carbonation. The calcium from fly ashes and brine both contribute to the formation of calcium carbonate during the carbonation reaction. Published by Elsevier Ltd.