CCS is a technology in which CO2 emissions from burning fossil fuels are captured, transported via pipelines and/or ships, and subsequently stored underground. Currently, there are a few large-scale CCS projects around the world, but these have not yet reached sufficient size to make a significant contribution to greenhouse gas (GHG) emission reductions. There are plans for CCS projects in the Netherlands, for example, the recent Porthos plan (Port of Rotterdam, 2017; Port of Rotterdam, 2018).
In total, CCS projects worldwide added up to around 30 Mt of captured CO2 in 2017 (IEA, 2019), compared to more than 37.1 Gt of total CO2 emissions in the same year (JRC, 2018). A considerable scaling-up the amount of CCS projects is required in order to achieve a substantial emission reduction.
There is an increasing interest not only to capture CO2 for storage but also to use it, for example, as a raw material in the industry (carbon capture and utilization, CCU). In some cases, the CO2 is used as is, such as in carbonated drinks. CO2 can also be used to enhance oil recovery by injecting CO2 into an existing oil well to increase pressure and reduce the viscosity of the oil. CO2 can be used as a raw material for the production of other materials and fuels. For instance, CO2 could be used in the production of cement or urea, although the costs and energy needs are still considered to be a major barrier (IEA, 2019).
The use of CO2 is potentially an important way to reduce emissions. The emission reduction does, however, depend on how long it takes before the CO2 is released into the atmosphere after use, how energy-intensive the use is, and what the emission intensity is of the application to be replaced by CO2 (IEA, 2019).
Most energy transition scenarios consider CCS and/or CCU as required contributions towards achieving emission reduction targets. This is partly due to the fact that for a number of industrial sectors – such as the steel, cement and chemical industries – there are not yet many alternative ways to reduce CO2 emissions on a large scale in the short term. CCS can already achieve a significant reduction in emissions in these industrial sectors.
Nevertheless, there are several arguments against CCS and CCU. Since CCS in some cases is such a relatively cheap way to reduce emissions, improving that technology also entails a lock-in risk, whereby cheap capture could slow down the process towards a fully sustainable energy supply. There are also worries about the safety of CO2 transport and storage(Selma et al., 2014). The use of CO2 as a raw material for chemicals or fuels is very energy intensive.
CCS and CCU can also contribute to a future energy system with net negative emissions. Negative emissions are important according to the recent studies of, among others, the IPCC (IPCC, 2018; Detz and Van der Zwaan, 2019). They form an essential part in the scenarios where global temperature rise is limited to 2 or even 1.5 degrees Celsius. Biomass captures CO2 from the atmosphere. Negative emissions can be achieved by growing more biomass, using this biomass for energy generation and storing the CO2 released underground. This is called bioenergy with carbon capture and storage (BECCS). Another option is to separate and store CO2 directly from the atmosphere with special installations.