Impact of system boundaries on the effectiveness of climate change mitigation actions: Dissertation

Despite international agreements, global greenhouse gas (GHG) emissions have not decreased according to the targets. Consequently, our generation is creating an enormous problem for future generations. As climate change is a global problem, GHG emissions must decrease globally. Consequently, international policies are needed, actions should be effective and the impacts should be assessed with broad boundaries. In Europe, the cornerstone of climate policy is the EU Emissions Trading Scheme (EU ETS) but the rebound impacts within the EU ETS are often excluded in the assessments. This dissertation examines the impacts of major CO2 emission reduction solutions with different system boundaries, highlighting the importance of boundary selection on the results. In addition, the economic feasibilities of the selected solutions are evaluated.The case examples represent the most important sectors in terms of global CO2 emissions, such as electricity and heat production, the steel industry and transport. The studied technologies include efficient Waste-to-Energy (WtE) concepts with high power-to-heat ratio, utilisation of CO2 Capture and Storage (CCS) in different applications, replacing steel mill blast furnaces with Oxygen Blast Furnaces (OBF), Combined Heat and Power (CHP) and Carbon Capture and Utilisation (CCU) for storable fuels, which can be used for example in transportation. The results highlight the importance of the consequences in the electricity production system as well as the rebound impacts in the EU ETS. For example, the studied concepts to decrease direct GHG emissions of steel mills lead to increased power purchase from markets and consequently increase in emissions of the power system. The impacts of CCU concepts based on electrolysis increase the emissions in electricity production but enable a decrease in the usage of fossil fuels in transportation. In addition, converting electricity to storable fuels enable higher shares of variable solar and wind energy in the power systems. The consequences in the power systems are complex, including for example the impacts on electricity imports and exports, future investments and the EU ETS. Even if these impacts can be recognised by qualitative means, unambiguous quantitative consequences cannot be given. Understanding the decisive impacts of the framework and boundaries is crucial to interpreting different assessments and making effective actions and policy decisions. Solutions which decrease emissions within a narrow system boundary can actually increase the emissions of the broader system.