Capture and sequestration of CO 2 from fossil fuel power plants is gaining widespread interest as a potential method of controlling greenhouse gas emissions. Performance and cost models of an amine (MEA)-based CO 2 absorption system for post-combustion flue gas applications have been developed, and integrated with an existing power plant modeling framework that includes multipollutant control technologies for other regulated emissions. The integrated model has been applied to study the feasibility and cost of carbon capture and sequestration at both new and existing coal-burning power plants. The cost of carbon avoidance was shown to depend strongly on assumptions about the reference plant design, details of the CO 2 capture system design, interactions with other pollution control systems, and method of CO 2 storage. The CO 2 avoidance cost for retrofit systems was found to be generally higher than for new plants, mainly because of the higher energy penalty resulting from less efficient heat integration, as well as sitespecific difficulties typically encountered in retrofit applications. For all cases, a small reduction in CO 2 capture cost was afforded by the SO 2 emission trading credits generated by amine-based capture systems. Efforts are underway to model a broader suite of carbon capture and sequestration technologies for more comprehensive assessments in the context of multi-pollutant environmental management. DOE/DE-FC26-00NT40935 i AcknowledgmentsThis report is an account of research sponsored by the

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Studies of CO2 capture and storage (CCS) from coal-fired power plants typically assume a capture efficiency near 90%, although the basis for a particular choice usually is not discussed. Nor do studies systematically explore a range of CO2 capture efficiencies to identify the most cost-effective levels of CO2 control and the key factors that affect such levels. An exploration of these issues is the focus of this paper. As part of the United States Department of Energy's Carbon Sequestration Program, we have developed an integrated modeling framework (called IECM-cs) to evaluate the performance and cost of alternative CCS technologies and power systems in the context of plant-level multipollutant control requirements. This paper uses IECM-cs to identify the most cost-effective level of CO2 control using currently available amine-based CO2 capture technology for PC plants. Two general cases are of interest. First, we examine the effects of systematically increasing the CO2 capture efficiency of an amine-based system for PC applications over a broad range. We report two measures of cost:  (i) capital cost and (ii) cost-effectiveness (cost per tonne of CO2 avoided) relative to similar plants without CCS. Second, we examine the cost-effectiveness of plant designs that partially bypass the amine capture unit so as to achieve low to moderate reductions of CO2, but at lower overall cost. Results from these cases are compared to the conventional case of a capture unit treating the entire flue gas stream. In each case, we identify the most cost-effective strategies and the key factors that affect those results.

Studies of CO 2 capture and storage (CCS) costs necessarily employ a host of technical and economic assumptions regarding the particular technology or system of interest, including details regarding the capture technology design, the power plant or gas stream treated, and the methods of CO 2 transport and storage. Because the specific assumptions employed can dramatically affect the results of an analysis, published studies are often of limited value to researchers, analysts and industry personnel seeking results for alternative assumptions or plant characteristics. In the present paper, we use a generalized modeling tool to estimate and compare the emissions, efficiency, resource requirements and costs of PC, IGCC and NGCC power plants on a systematic basis. This plant-level analysis explores a broader range of key assumptions than found in recent studies we reviewed. In particular, the effects on cost comparisons of higher natural gas prices and differential plant utilization rates are highlighted, along with implications of financing and operating assumptions for IGCC plants. The impacts of CCS energy requirements on plant-level resource requirements and multi-media emissions also are quantified. While some CCS technologies offer ancillary benefits via the co-capture of certain criteria air pollutants, the increases in specific fuel consumption, reagent use, solid wastes and other air pollutants associated with current CCS systems are found to be significant. To properly characterize such impacts, an alternative definition of the "energy penalty" is proposed in lieu of the prevailing use of this term.