Carbon dioxide (CO2) is the main contributor to climate change and thereby to global warming. Several technologies have been proposed to reduce atmospheric CO2 emissions, such as CO2 capture and storage (CCS), CO2 capture and utilization (CCU) and hydrogen production. From these proposals, converting the captured CO2 into valuable products was seen as a promising area to explore. Correspondingly, CCU is achieved when the captured CO2 is utilised to produce chemicals and fuels that are more environmentally friendly than their fossil-based ones. Yet, the cost of hydrogen and the energy consumption associated are key issues to deal with. This thesis aims to understand and explain the role of hydrogen production, CCS, and CCU in the sustainability context.
The first part of the study focused on the hydrogen production pathways as a crucial component in the decarbonisation of the transport, heating, and chemicals sectors. A linear optimisation model was built to explore carbon-neutral shares of all the investigated production routes in terms of their total cost that included the externalities plus the economic performance. The results supported an approach for establishing strategies for the much-needed energy transition by promoting blue (fossil-based with CCS) hydrogen at present until green hydrogen becomes competitive.
The second part focused on evaluating the best use of wind energy between the CCU route to methanol from CO2 and hydrogen to be used as a fuel in the transport sector or to decarbonise the electricity mix directly considering the energy systems constraints through scenario-based modelling. It was concluded that, at present, decarbonising the electricity grid using renewable energy sources with CCS would offer greater environmental benefits, without incurring large changes indirect economic costs, compared to producing methanol from the hydrogenation of captured CO2.