CO2 Mineral Sequestration Studies in US

Carbon sequestration by reacting naturally occurring Mg and Ca containing minerals with CO2 to form carbonates has many unique advantages. Most notably is the fact that carbonates have a lower energy state than CO2, which is why mineral carbonation is thermodynamically favorable and occurs naturally (e.g., the weathering of rock over geologic time periods). Secondly, the raw materials such as magnesium based minerals are abundant. Finally, the produced carbonates are unarguably stable and thus re-release of CO2 into the atmosphere is not an issue. However, conventional carbonation pathways are slow under ambient temperatures and pressures. The significant challenge being addressed by this effort is to identify an industrially and environmentally viable carbonation route that will allow mineral sequestration to be implemented with acceptable economics. Under the sponsorship of the U.S. Dept of Energy, a team of researchers from the National Energy Technology Laboratory, Albany Research Center, the Los Alamos National Laboratory, and Arizona State University was formed in the summer 1998 to investigate and improve the carbonation process. This paper discusses significant progress achieved by the team in searching for faster reaction methods using: magnesium silicates, supercritical CO2, water, and additives; in searching for pretreatment methods to enhance mineral reactivity; and in analyzing the structural changes to identify reaction paths and potential barriers. The paper also discusses plans to construct larger scale operating units (up to several MWe ) in order to validate the method as a viable sequestration tool at industrially relevant scales.