Carbon dioxide utilisation – what is it and why it should be promoted?
Carbon capture and utilisation (CCU) describes processes in which CO2 is captured (from point sources or air) and is then used as a raw material for value-added products. In other words, CO2 is considered a resource, rather than a harmful greenhouse gas. CO2 can be used e.g. in the production of synthetic fuels, bulk and specialty chemicals as well as polymers, and construction materials through mineralisation.
The three major drivers for CCU are
- reducing the dependency on fossil resources by broadening the resource base,
- climate change mitigation and
- enabling higher penetration of intermittent renewable electricity.
From fossil to renewable and recycled resources
CCU enables sustainable product alternatives utilising only renewable or recycled raw materials and energy. This will help reducing import dependency on fossil feedstocks and increasing energy self-sufficiency and security. Furthermore it promotes transition to a circular economy and offers new business opportunities.
CCU can also enable "indirect electrification" of processes and products that are difficult to decarbonise via direct electrification. For example electric drive is a feasible solution for passenger cars but aviation and heavy trucks will depend on liquid fuels for years to come – a business opportunity for CCU.
Assessing climate impact of CCU calls for life cycle analysis
Carbon Capture and Utilisation is closely related to Carbon Capture and Storage (CCS), but their impact on CO2 emissions is different. In CCS CO2 is captured and permanently stored in geological formations while in most CO2 utilisation applications – such as production of fuels or chemicals – CO2 is eventually released into the atmosphere. The climate benefit of such CCU applications comes from the fact that they can reduce the use of their fossil counterparts. Ultimately, the goal should be to use biogenic CO2 or capture it directly from air to provide a fossil-free source of carbon.
Another important aspect to remember is that as CO2 is an end-product of combustion, it does not contain energy. Thus production of fuels from CO2 requires an energy source which is typically electricity. The emission factor of electricity will have a crucial impact on the overall climate impact of such fuels.
The CCU technology portfolio is wide and diverse and so are the related climate impacts. Important factors to consider include the product lifetime, the energy consumption and source, and the CO2 intensity in the replaced fossil product. To guarantee a significant positive climate impact of a CCU process, a life cycle analysis (LCA) should always be carried out.
Enabling higher shares of intermittent wind and solar power
One of the main challenges for 100% renewable energy system having high shares of wind and solar power is to manage the balance between energy supply and demand. For this better interconnectivity of grids, demand side response and energy storages are needed. Producing synthetic fuels from CO2 and electricity at times of excess electricity generation offers one attractive solution, especially for long-term/seasonal energy storage.
CCU enables utilising carbon dioxide in products – but not all of it!
Compared to global anthropogenic CO2 emissions the potential of CO2 utilisation is quite limited (Figure x). The estimated long-term potential is one magnitude and the current utilisation two magnitudes lower than the anthropogenic CO2 emissions. [1,2] Currently vast majority of the utilised CO2 is used for synthesis of urea and inorganic carbonates and for boosting methanol production.  These applications, however, bind only the CO2 that was released by earlier production steps. The 'true CO2 utilisation applications' are just beginning to emerge and thus offer vast growth potential. Still, CCU alone will not solve the climate change problem but can still play a significant role - battling climate change calls for a combination of various technologies.
 von der Assen, N. et al (2016). Selecting CO2 Sources for CO2 Utilization by Environmental-Merit-Order Curves, Environmental Science & Technology, 50 (3), pp. 1093-1101.
 Aresta, M. et al. (2013). The changing paradigm in CO2 utilization, Journal of CO2 Utilization, 3–4, pp. 65–73.