Carbon capture and geological storage
Human activities involve the use of fossil resources that generate CO₂ emissions when burned. In addition, some chemical or industrial processes (such as cement) are natural CO₂ emitters.
Therefore, a non-negligible share of CO₂ will continue to be emitted by humanity, despite the deployment of solutions such as energy efficiency, the migration of consumption towards thermal or electrical renewable energies.
Thus, in the objective of decarbonising our activities to achieve carbon neutrality, the capture, industrial use or geological storage (CCUS, Carbon Capture Utilization and Storage) of CO₂ could play an interesting role, which is evaluated at 10% of the efforts towards a low-carbon economy by the IEA (International Energy Agency).
Isolate the CO₂
The first step is to isolate CO₂ from other molecules. Four main processes have been developed :
- Post-combustion : capturing the CO₂ after combustion in the flue gas of the chimneys. CO₂ is relatively low in concentration, in a large volume of effluent at low pressure. Techniques such as chemical absorption (amine scrubbing) or membrane separation have been used industrially since the 1960s. This technology is particularly suitable for retrofitting and would find its place in many existing processes.
- Pre-combustion: isolating the CO₂ before combustion through the production of a synthesis gas (syngas) which will contain a high proportion of hydrogen. Much research is underway, and R&D is developing several technologies. The most promising application would be the production of electricity.
- Oxy-combustion : using oxygen as an oxidiser and not air as is conventionally the case. The problem is then shifted to the production of O2, which implies energy-intensive processes and a modification of the equipment (adapted burners, metallurgy to withstand the high temperatures).
Capture within industrial processes : As mentioned above, CO₂ is naturally emitted by processes, notably oil and gas production. Thus, the first CCS applications emerged in oil contexts, where CO2 is naturally produced with methane molecules. To a lesser extent, methanisation has the same characteristic, where operators are obliged to purify the biogas according to the chosen energy use.
Capturing the CO₂
Once the CO₂ has been isolated from the other components, it can either be used for on-site or remote industrial production, or injected into depleted reservoirs : the hydrocarbon resources it contained have been produced. As the oil industry has a very good knowledge of these reservoirs, this would limit the risks of leaks, or mobility of CO₂ out of areas under control.
This technology is subject to several criticisms for the fears it inspires in the management of risks linked to the subsoil, but also for the concern that it will not be ready in time to meet the targets for reducing CO₂ emissions.
Nevertheless, many scientists are working on the subject. Indeed, since 1996, the Norwegian oil operator Statoil has been storing quantities of CO₂ in the Sleipner field, offering almost 30 years of monitoring and control of the fluid’s behaviour.
In the absence of geological storage, it is also possible to think about uses for CO₂ molecules. For example, the synthesis of urea requires a molecule of CO₂ and ammonia (NH₃).
Validation criteria for voluntary carbon offsetting
To implement a CO₂ capture project, Orygeen will :
Assessing the industry’s sensitivity to the carbon constraint
Define the appropriate strategy, including the role that the CCUS could play
Investigate technical options
Consult with capture technology providers
Organise the R&D project where appropriate
Suggest uses for CO₂ and propose operators for storage