Analysis and design of carbon dioxide utilization systems and infrastructures

Abstract

Carbon dioxide (CO2) is an important chemical compound for life on earth, as it enables photosynthesis in plants and other organisms. It is also commonly utilized in many applications and products, such as carbonated drinks, welding gases, food preservatives, fire extinguishers, and coffee decaffeination. The concentration of carbon dioxide in the atmosphere has increased due to human activities related to the combustion of fossil fuels and other industrial activities. Because carbon dioxide contributes significantly to climate warming, its release into the atmosphere needs to be curbed in order to limit the harm done to the Earth’s ecosystem.

In parallel with other climate change mitigation measures, carbon capture technologies could offer further pathways to reduce CO2 emissions. In principle, these may be divided into two subgroups: sequestration technologies and utilization concepts. Carbon capture and sequestration (CCS) aims to permanently store CO2 in underground formations and thus deny its climate warming impact. Carbon capture and utilization (CCU) instead targets different products and materials that could bind the carbon, either permanently or for a shorter time. To date, there are tens of different applications where CO2 is crucial, yet the global utilization volumes are still modest compared to what they are estimated to be in the future.

This dissertation evaluates the challenges and opportunities related to CCU, focusing on fuels and chemicals due to their large utilization potential. The work addresses the volume and geographic availability of CO2 sources in Finland and presents possible scenarios for future CO2 utilization. Main infrastructural challenges and options related to the transportation and storage of CO2 are also evaluated. Dynamic simulations of different plant configurations and operation strategies are used to analyse system performance and to identify possible links to heat and power systems. Integration of CCU into a pulp mill is studied as an example case to evaluate the economical profitability of CO2 utilization.

The analysis confirms that CCU holds great opportunities for reducing emissions and producing massive amounts of hydrocarbon products. Finland and Sweden both have exceptional volumes of biogenic CO2 available, to the extent that available electricity will be limiting the conversion processes. These feedstock challenges could partly be alleviated by significant investments into infrastructure development, which would level the resource discrepancies between regions. Challenges relating to CO2 transport, even in large volumes, are primarily related to legislation rather than technology. Dynamic operation of the production plants presents additional challenges, so intelligently designed buffer storage and flexible operation strategies could enable significant cost reductions. Residual heat from electrolysers and synthesis processes could be utilized to increase efficiency and profits, but the risk of local oversupply situations is also evident. Renewable premiums and other support systems for CCU are likely necessary in the short term to enable the forming of a mature market for CO2 and products derived from it.