Carbon Capture, Removal, and Storage
Summary
Carbon capture, removal and storage technologies are essential to most net-zero scenarios. As warned by the 6th IPCC synthesis report, we are likely to reach 1.5°C of warming in the first half of the next decade no matter what happens with GHG emissions. To ensure that we do not blast through this threshold, immediate and drastic emissions reductions must occur, and all projections to achieve this require some kind of carbon capture, removal and storage. However, these technologies are not yet mature and there are only just over 25 facilities operating around the world.
Published: 3 May 2023 by Jessica Wen
Technologies
The three different types of carbon capture, removal, and storage technologies are:
Carbon capture and storage (CCS)
Carbon capture and use/utilisation (CCU)
Carbon dioxide removal (CDR)
Figure 1 illustrates the difference between CCS, CCU, and CDR technologies. These technologies are explored in further depth in the next sections.
Figure 1: Differences between Carbon Removal, CCU and CCS (cr.hub)
Carbon Capture and Storage (CCS)
Carbon capture and storage (CCS) is the class of technologies that prevents fossil fuel emissions from entering the atmosphere in the first place, but does not remove any emissions from the atmosphere. This is not a negative emissions technology, and CCS alone is not a solution that will bring us to net zero. As a result, we do not think that CCS is the most effective technology to work on as an engineer.
Carbon Capture and Use/Utilisation (CCU)
Carbon capture and use/utilisation (CCU) refers to technologies that produce fuels and other products from captured carbon dioxide. To become a negative emissions technology, the source of the captured CO2 and the life cycle of the product must be considered.
Carbon Dioxide Removal (CDR)
Carbon dioxide removal (CDR) technologies take carbon dioxide straight out of the air. These are the most likely to become the negative emissions technologies that are necessary to tackle climate change. With low confidence, we believe that CDR is most important and neglected of these carbon capture, removal and storage technologies, and the current bottlenecks in development and deployment are very technical.
As outlined in this primer on CDR, none of these technologies are “the solution” by themselves
“The true solutions will be the community-to-global-level social, political, and organizing actions for the future of our climate, and the collaborative effort to design, finance, and create carbon dioxide removal projects that work in harmony with sustainable energy, agriculture, forestry, and waste systems.” (CDR primer)
In short, as Giving Green outline, “GHG mitigation should be our first priority, and [...] CDR is a necessity to reduce GHG levels beyond what mitigation alone can accomplish”.
There are many different ways to remove carbon dioxide from the atmosphere:
Afforestation and reforestation
Soil conservation, biochar and enhanced weathering
Direct air capture (DAC) and storage/sequestration
Ocean kelp farming, algae growth and seawater zapping
Bioenergy + carbon capture and storage
Risks of working in carbon capture, removal, and storage
There is a risk of carbon capture being used for enhanced oil recovery (EOR) and other fossil fuel interests, which is probably net harmful.
EOR is the process of injecting carbon dioxide into oil wells to extract oil that cannot be extracted by the usual means. Much of the carbon captured through the above techniques is used for this purpose because EOR is by far the most economically valuable use for CO2.
EOR reduces the carbon footprint of oil, but may extend oil production beyond what would otherwise be financially possible, leading to higher emissions in the long run. This is the subject of great debate in the climate community. Due to this uncertainty in the true impact on CO2 emissions, HI-Eng agrees with Giving Green’s assessment and does not recommend doing work in carbon capture for EOR.