Life Cycle Assessments of Carbon Capture Pathways: A Hybrid Meta-Analysis Approach

Efforts to slow the rate of carbon emissions into the atmosphere are driving research and development into carbon capture and storage (CCS) technologies from stationary sources, primarily power plants. In CCS, the carbon from fossil fuels would be captured and sent to some permanent repository other than the atmosphere. Lifecycle assessment (LCA) is a tool for quantifying the energy flows, emissions and other environmental impacts of technological pathway and it has been applied to several of the leading CCS pathways. These pathways differ in the fuels used in power plants (i.e., coal or natural gas), capture methods (i.e., chemical absorption or membrane separation), and capture type (i.e., post-combustion, pre-combustion or oxyfuel combustion). The lifecycle impacts of several common pathways, such as post-combustion CO₂ capture using amine-based solvents from the flue gas of coal-fired power plants have been examined. Despite similar system boundaries and apparently comparable consumption of resources that are reported in various studies, the lifecycle results of these pathways vary widely and contain large discrepancies. This is because few commercial examples of these pathways exist from which to obtain data and in part because of differences in modeling assumption and scopes. Here we harmonized these studies and incorporated first-principles analysis and data from various lifecycle studies, to determine the net energy and greenhouse gas impacts of different CCS pathways. Our analysis suggests that when the results of impact factors (such as the global warming potential) from these different studies are normalized to a common functional unit and corrected for the burdens of various unit processes in the full lifecycle, they show a similar range of values, as opposed to the widely divergent results originally reported in the studies. We also incorporate LCAs of relatively new capture techniques such as MECC membranes and the oxyfuel combustion capture route.