Understanding environmental trade-offs of carbon capture, utilization and storage

Abstract

Climate change caused by the rise of anthropogenic greenhouse gas (GHG) emissions is one of the challenges mankind has to face in the coming years. The deployment of carbon capture and storage (CCS) and potentially CO2 utilization (CCU) technologies are needed to limit climate change. These technologies aim to capture CO2 from power and industrial processes and store the CO2 long term or utilize the CO2 into useable products. Integrating CCS with the use of biomass (BioCCS) can be particularly interesting, as in total CO2 can be removed from the atmosphere, and is considered necessary for ambitious climate change mitigation targets. CCS and CCU can reduce CO2 emissions, but often leads to an increase in other environmental impacts as a result of (fossil) energy needed for capturing, transporting and utilizing the CO2. It is important to understand the environmental trade-offs between climate change mitigation and other environmental impacts when considering the deployment of CCS and CCU technologies. This thesis focusses on three areas that are increasingly gaining attention, i.e.: the impact of CCS on water availability, the effect of different types of biomass on the environmental trade-offs of BioCCS, and environmental impacts of CO2 utilization. The impact of CCS on water availability is studied on both a process and system level. Life cycle assessment (LCA) studies are carried out for different case studies (power plant and industry) that include the water depletion potential of the instalment of CCS. The results show that the deployment of CCS can substantially increase the water depletion potential of a process, as a result of increased water use on site for cooling and CO2 capture processes, and a rise in water use caused by the production of additional fuel. A system level analysis highlight that equipping a large part of European power plants with CCS in 2050 can significantly increase regional water stress levels across Europe. The environmental impact of BioCCS is analysed at power plant level and on a life cycle basis. Results show that the integration of biomass use to CCS further increases the climate change mitigation potential of CCS. Changes in impacts in other categories are limited, although replacing coal by biomass can also lower for example toxicity and eutrophication impacts. The environmental performance of a specific CO2 utilization route (CO2 conversion into DME) is analysed in this thesis. Results indicate that the environmental performance improvement of this option is limited, but also highlight limitations in CCU performance assessment of existing indicators. Therefore, a new indicator, the Specific Primary Energy Consumption per unit of Fossil Fuel Replacement (SPECFER), is introduced. This indicator measures the energy efficiency of CO2 conversion and allows to evaluate and compare the performance of CCU options with different functionalities.