Lawrence Berkeley National Laboratory

The intent of geologic carbon dioxide (CO2) sequestration, also known as "geologic carbon sequestration," is to prevent anthropogenic CO2 from entering the atmosphere, thereby maintaining acceptable levels of atmospheric CO2. Ideally, the CO2 will be safely transported to sequestration sites and injected deep underground, where it will be permanently trapped, with no negative impact on the terrestrial environment or on underground resources such as groundwater or fossil fuel deposits. In practice, carbon sequestration will be neither perfectly effective nor risk-free. There are risks associated with geologic carbon sequestration, and evaluation of these risks will be important for making decisions concerning where and how sequestration should be performed. The goal of a risk assessment is to quantify the likelihood of harm (or loss) and to present the results in a format that assists decision makers who must act to tolerate, mitigate, or eliminate the potential harm. The goal of risk management is to establish the practical significance of the assessed risks, compare the costs of reducing these risk to benefits gained, compare the risks to the societal benefits derived from incurring the risk, and to establish political and institutional processes of reducing risks. This section summarizes the risk assessment approaches and risk management methods that can be applied to study geologic carbon sequestration in California, including CO2 capture, transportation and storage operations. It includes consideration of human exposure limits, pathways for human and environmental exposure during operations and post-operations, and how risks change over the time scales associated with storage as the CO2 migrates and reacts in the subsurface environment.