Sustainability assessment of large-scale carbon capture and sequestration deployment outside the system boundaries - Opportunities and challenges

Most power generation in the United States is derived from the combustion of fossil fuels, primarily coal and natural gas. As a result, greenhouse gases (GHGs) are generated, and they act to trap radiant heat from the Earth. When GHGs are discussed, attention is usually concentrated on carbon dioxide (CO 2) because it is believed to be the most manageable anthropogenic GHG. Therefore, introducing new technologies, primarily those which deal with CO 2 capture and storage, is seen as a potential option for managing GHGs. Oil and gas reservoirs, saline formations, and un-mineable coal beds are examples of underground CO2 storage sites. In the United States, it has been estimated that these sites together have the potential capacity to store the country’s CO2 emissions for the next 500 years. For this reason, carbon capture and sequestration (CCS) has become a very attractive approach by several industries, including the coal-fired power industry, to reduce their GHG emissions. However, the implementation of CCS on a broad scale will require an enormous input of resources and energy, which will be used during the CCS production, installation, and operation phases. The eventual result of this implementation will be an increased demand for fuel, which in turn will lead to further mining activities to provide the additional energy required. Input materials such as pipelines, water, and chemicals are also required throughout the technology’s life cycle. According to the literature, CCS with a post-capture system reduces the total CO2-equivalent (CO2-e) emissions of a coal power plant by 65% to 87%. The magnitude of this reduction depends on the study boundaries that are considered in the life-cycle assessment (LCA), and on other parameters considered in the study, such as the plant’s power-generation thermal efficiency and capacity, fuel type, raw material transportation method, distance to power plants, distance to storage sites, and depth of storage sites. This dissertation address this issue and uses the LCA harmonization approach with the aim of reducing the variability observed in the published literature, particularly, for amine-based post-combustion CCS technologies on coal-fired power plants. The levels of GHG reduction, both the published and harmonized results indicated a large decrease in global warming potential (GWP) for the various coal-fired technologies examined. However, because of the requirements of energy and other input materials, there was a notable increase in cumulative energy demand (CED), which would subsequently increase the footprint of the technology in term of resources. To expand the foreseen benefits of CCS and widen it applications, CCS integration with EOR was investigated from an LCA-GIS perspective in which the CO2 is utilized from ethanol, coal-fired, and natural gas power plants in the lower 48 states of the U.S. the results indicated that that crude oil with lower carbon intensity can be produced from EOR reservoirs that are less efficient in terms of crude recovered per ton of CO2 injected. However, it should be acknowledged that using less efficient reservoirs would be associated with greater CO 2 supply which has a parasitic energy requirement and would in turn entail a higher cost burden. With a focus of future CCS deployment in the U.S., the game-theory approach was applied to determine the impacts of possible changes in carbon policies, the carbon market, and the cost of CCS technologies on the decisions of industrial carbon emitters. In conclusion, CCS have great potential to reduce the carbon intensity of electric or transportation fuel. However, under existing carbon policies and at the current cost of CCS deployment, the strategy of the ethanol industry would be dominated by CCS deployment. By contrast, coal power plants would not have sufficient governmental or economic incentives to deploy CCS because of the gap between the cost capturing and transporting CO2 and the price of CO2