Carbon capture and storage, how does it work?


The development of renewable energies and energy efficiency are two essential pillars of efforts to mitigate climate change.

But, in view of the magnitude of the reduction in emissions to be achieved, the experts of the International Energy Agency(OUCH) and IPCC consider that the use of CO capture, storage and recovery technologies2 is essential to achieve the objective of carbon neutrality.

The DMX CO capture process2, the fruit of a decade of research in the laboratories of IFP Énergies nouvelles, is now being demonstrated on the site of Arcelor Mittal in Dunkirk, a steel giant that emits more than 11 million tonnes of CO2 every year.

CO2 captured could be transported and then stored in the North Sea, for example on the site of the Norwegian project Northern Lights, who also signed last August its first commercial agreement for the transport and storage of CO2, this time captured on an ammonia and fertilizer plant in the Netherlands.

The objective of capturing, storing or recovering carbon dioxide (better known by the acronyms CCS or CCU for carbon capture and storage ou carbon capture and use) is to help decarbonize industry: it is a set of technologies for capturing and storing and/or using CO2 rather than letting it escape into the atmosphere. In fact, heavy industry is the source of almost 20% of global COXNUMX emissions.2 today. In France, the National Low Carbon Strategy (SNBC) sets a reduction of industrial emissions by 80% by 2050 compared to 2015.

In the IEA's "sustainable development" scenario, these capture technologies would contribute 15% to the cumulative reduction of CO₂ emissions in 2070.

How ? By separating the CO2 industrial fumes, to store it in deep underground geological formations and thus isolate it from the atmosphere, or to use it as a resource in the production of biofuels or fertilizers, for example.

About thirty large-scale installations are currently in operation around the world to decarbonize electricity production (coal power plant, gas power plant) and industry (steel, cement, chemicals) and 35 to 40 million tonnes are captured and stored annually, compared to the 34 billion tonnes of CO2 that were issued in 2020. It is estimated that it would take capture and store 50, or even 100, times more by 2035 to meet carbon neutrality objectives – which calls for the deployment of CCUS on a large scale, in Europe and worldwide. Given the current maturity of technologies, this is possible by 2030.

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First step in the chain: capture

Capture technologies have been operational for decades, particularly for certain applications such as thermal power plants, but they are still expensive. Of new, less energy-consuming and more efficient processes are thus tested within the first demonstrators like that of Dunkirk. Today, it is also a question of integrating these processes into a dedicated sector.

There are three main families of processes. The first, “post-combustion” capture, consists of extracting the CO2 industrial fumes from the combustion of fossil resources (wood, natural gas, oil and coal) using a solvent which has a affinity for CO molecules2. Positioned downstream of industrial processes, this technology can be implemented on pre-existing installations and applied to the treatment of fumes from various industries. If the capture rate exceeds 90% of the CO₂ emitted, it is nevertheless accompanied by a high "energy penalty" required during the separation of CO2 solvent, which leads to a high implementation cost, i.e. between €10 and €100 per ton of CO2 avoided (and therefore not issued).

The second family, called “oxy-combustion” capture, consists of carrying out combustion in the presence of (almost) pure oxygen, rather than in air. The combustion gas thus produced consists almost exclusively of water vapor and CO2. It is then much simpler to extract the CO2 than when diluted in nitrogen from the air. This technology thus presents a lower energy penalty but requires a retrofit of the combustion chamber. It is therefore envisaged for certain applications, such as cement plants, and for new biomass and fossil fuel conversion units.

Finally, the third family, called “precombustion” capture, consists of extracting CO2 upstream of combustion by transforming the initial fuel into a “syngas”: this involves gasifying the fuel to obtain a mixture of CO + H20, then to carry out a chemical transformation to obtain a mixture CO2 + H2 and finally to extract CO2 by solvent. The implementation of this process needs to be integrated upstream, at the time of the construction of the industrial unit.

This process captures CO2 at the level of industrial installations, but also of remove CO₂ present in the atmosphere as at the Orca site in Iceland (which should capture about 4000 tonnes per year).

How to transport CO₂ and store it?

Further down the chain, CO2 is transported in the same way as natural gas, by gas pipeline, train or boat, depending on the quantity of CO2 to transport and distance. Transport and storage infrastructures therefore do not pose any particular technical problem, but they must be secure and ensure their maintenance, as required by any industrial equipment.

Then the CO2 captured is stored in old hydrocarbon deposits or porous rocks (deep saline aquifers). CO2 is injected in dense form at a depth of at least 800 meters. He is then trapped by chemical and geological mechanisms : dissolution in the brine (salt water) present in the rocks, immobilization in the pores of the rocks, then, eventually, mineralization.

Underground storage capacities in Europe are roughly estimated to 300 billion tonnes, the equivalent of 100 years of global emissions in 2019, but we still need confirm these capacities and the integrity of the sites so that operational CO storage projects2, like that of Northern Lights, may emerge.

The storage sites are subject to rigorous selection in order to guarantee the sustainability and security of storage over the long term (migration of CO2 outside the storage site). Storage operations are accompanied by a monitoring protocol which includes, among other things, geophysical monitoring of the behavior of CO2 in the subsoil, gas measurements and sampling at depth in the subsoil and on the surface, monitoring of microseismic events, etc.

What economic models for the deployment of these technologies?

The benefit of the deployment of these sectors is essentially linked to the reduction of CO emissions2, to which carbon markets for example (emission quota systems) give an economic value: capture, transport and storage or recovery are not technologies independent of each other, but links in a same value chain.

This is why the deployment of the sector must be coordinated over time and on a voluntary territory by means of investments in shared operational projects on the scale of France and Europe. The deployment of “CO hubs2 – networks collecting CO2 issued by different industries and pooling transport and storage infrastructures – must be anticipated. This is the case, for example, of Hauts-de-France and Normandy, which are working on the development of a hub for the capture and transport of CO2 and projet Northern Lights which is working on a commercial CO transport and storage project2.

Developed within the framework of European research projects such as Strategy CCUS based on technical factors (volumes of CO2 involved, geographical areas concerned, possible uses of CO2 near capture sites, possible storage sites) and environmental (via life cycle analysis methodologies), the scenarios also take into account economic and social factors, such as job creation and the concerns of local communities, which must be involved as soon as possible in the construction of a project.

The challenge today is to create the conditions to allow the deployment of the CCUS sector on a large scale from 2030. If the technologies are there, financial support mechanisms and a regulatory framework are necessary to accelerate the implementation of the sector. According to current estimates, the carbon quota price emitted is still lower than the expenses that manufacturers would have to incur to invest in these facilities, i.e. between €50 and €180 per ton of CO2 avoid.

Florence Delprat-Jannaud, CO2 Capture and Storage Program Manager, IFP New energies

This article is republished from The Conversation under Creative Commons license. Read theoriginal article.

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