Six major CCS challenges - and ways of overcoming them
November 2025
Carbon capture and storage is a complex flow process with many challenges along the way.
Get an introduction to six major ones, and learn how to overcome them and design a plant that will keep running safely and efficiently. This article focuses on challenges seen from a pumping and fluid-handling perspective and is based on DESMI’s experience from CCS and CO₂ handling projects.
Carbon capture and storage (CCS) is an important technology for reducing CO2 emissions to the atmosphere and reducing the climate impact of greenhouse gases.
There are three main process steps involved in CCS:
| 1. | Capturing gaseous CO2 from flue gases, then compressing and, if required, liquefying it for transport or storage | 2. | Transporting the liquid CO2 | 3. | Injecting it into storage deep underground (or using it) |
Many CCS processes rely on fluids like amines or bicarbonates to extract CO2 by bonding with the CO2 molecules. However, handling amines, bicarbonates, and liquid CO2 involves challenges that can significantly reduce plant efficiency or lead to equipment malfunction if they are not addressed.
In the following, we look at some of these challenges and discuss ways of overcoming them through a combination of suitable equipment and careful plant design.
#1 - Corrosion
The solvents used in CCS, including MEA, MDEA, CDRMax, and hot potassium carbonate, and ammonia, are often toxic and aggressive. They corrode metals through chemical reactions, causing wear, premature breakdown, higher maintenance cost, and reduced system efficiency.
To safeguard your system, you need to use pump, pipe, and valve materials that can handle the specific sorbent you are planning to use. AISI 316 stainless steel can be suitable for moderate amine service, but more resistant alloys such as duplex or Alloy C-276 may be required at higher temperature or oxygen exposure.
Deciding on the right equipment, however, is about more than materials. Reliable sealing, too, is critical for the safe, efficient, and long-term operation of CCS systems as it contributes to leak-free performance, maximum durability, and operational efficiency. Depending on your requirements, you could opt go for a compact and cost-effective single seal, a robust and durable double seal, or a fully enclosed, seal-free less magnetic coupling that transfers torque using industrial magnets and provides completely leak-free performance.
Under certain conditions, liquid CO₂ can also cause erosion or cavitation damage: When pumps create suction in the liquid, it can revert to the gas phase. This leads to cavitation erosion that corrodes the material around the suction port of the pump. In addition to wearing out the pump, this creates unwanted flow fluctuations.
This phenomenon is primarily avoided through careful design: You must size your pumps to the available suction pressure (NPSHa), using pumps with NPSH values well below the NPSHa values of your system. We recommend involving the pump supplier early in the process to contribute to the design of pipes, tanks, valves, and pumps.
#2 - Foaming
When your solvent has absorbed CO₂ (and is therefore a rich solvent), it can release gas or form foam – mainly in absorber and stripper columns, but also in piping and pumps if the solvent is degraded. Two phenomena can occur:
Degassing: Dissolved CO2 comes out of the solvent if the pressure drops significantly (for example, just before a pump) or if the liquid is agitated. This can create gas pockets that interfere with the pump, reduce hydraulic efficiency, and increase the risk of corrosion.
Foaming: Stable foam can form if the solvent contains degradation products, particles, or contaminants, which act as surfactants. Foaming reduces the effective liquid volume and can further disrupt pumping and process control.
The solution is to design your pumping system to maintain stable flow and pressure so that the rich solvent is transported calmly, minimising pressure shocks and agitation. Variable speed drives can help match pump performance to actual demand, and control valves can stabilise flow.
It is also important to monitor solvent quality and replace it when necessary. All solvents degrade over time, especially amine-based ones like MEA when exposed to heat and oxygen, making them more prone to both degassing and foaming. Proper maintenance and solvent management are key to maximising system efficiency. Chemical antifoaming agents and regular solvent reclamation are also important to maintain stable operation.
#3 - Crystallization
Bicarbonate solutions are generally less aggressive than amines, but they can cause local crystallization, typically around mechanical seals or in areas where temperature fluctuations create cold spots.
Here, small leaks or local cooling can cause the bicarbonate to come out of solution and form crystals, which over time may increase pump wear or even lead to partial blockages. Maintaining a stable temperature profile and avoiding cold surfaces are key design considerations for pumps and seal-flushing systems in carbonate-based CCS processes.
System efficiency can be impacted, but the issue is usually preventable through careful system design. Maintaining a stable temperature profile and avoiding excessive heating is important, as high temperatures can break down bicarbonates into gaseous CO2 and carbonates, both of which reduce efficiency and can contribute to crystal formation. Keeping the correct bicarbonate concentration in the solvent also helps to minimise crystallization risk.
#4 - Variable fluid viscosity
Viscosity is a liquid’s resistance to flow – and to being pumped. All flow systems are designed to handle liquids of a certain viscosity. In CCS systems, the viscosity of the solvent changes depending on where it is in the process: When it has absorbed CO2 from the flue gas, it is more viscous than in its lean state.
High-viscosity liquids are not in themselves hard to handle; many pump manufacturers offer pumps that are well suited for highly viscous liquids. The challenge is to be aware that the properties of the solvent change, and to design a system that can handle varying liquid viscosities.
Pumps generally need more power to handle highly viscous liquids, and not all pump types are equally well suited.
Centrifugal pumps lose efficiency at higher viscosity because of increased internal friction and flow resistance, while positive displacement pumps handle high-viscosity fluids better since they move a fixed volume per cycle regardless of viscosity.
However, most CCS systems operate within the workable range for centrifugal pumps when designed correctly, taking viscosity-related power demand and reduced efficiency into account.
You should also note that high-viscosity fluids can cause excessive wear on pump components such as seals and bearings; that they can increase the risk of cavitation; and that they tend to generate more heat in the system. Your pump maintenance schedules should reflect this, and since CCS is a temperature-sensitive process (because solvents and CO2 need to attain specific temperatures for the process to work), your overall system design should take heat generation into account.
The higher viscosity of CO₂-rich solvents reduces pump efficiency and increases power demand; this should be considered when sizing motors and assessing energy balance.
#5 - Dry ice formation
When captured CO2 has been compressed and cooled to its liquid state, it needs to stay liquid for transportation and storage. If it goes back to its gas phase, it can cause cavitation as described above; conversely, it can also solidify as dry ice, forming crystals that can block pumps and valves and reduce system efficiency.
Dry ice formation mainly occurs in cryogenic or liquefaction steps rather than in amine-based capture systems, where temperature and pressure are carefully controlled. You can prevent this from happening by sizing the pump correctly and designing the system in such a way that the correct pressure and temperature to keep CO2 in its liquid state are always present.
If dry ice does form in the system and blocks pumps, DESMI NDW deepwell pumps feature a reversible operation mode that allows the pump to run backwards and clear ice from internal components. This proprietary design provides a practical way to restore flow in cryogenic CO₂ applications where pressure and temperature fluctuations can lead to dry-ice formation.
In cryogenic carbon capture, dry ice formation is part of the capture process. In this particular step, dry ice is actually desirable, but as soon as the captured CO2 has been converted to liquid, it needs to stay liquid as described above.
#6 - Nitrous and sulphur oxides
Depending on the fuel used at the facility (biofuels, coal, or waste, for example), the amount of liquid in the flue gas can vary – and so can the nitrous and sulphur oxide (NOx and SOx) content. Not only do these oxides cause pollution and health issues if emitted to the atmosphere; they can also degrade the quality of solvents used in the CCS process, particularly amines.
For these reasons, you should take steps to remove them from the flue gas using a scrubber system or similar. Once again, the general design of the CCS plant needs to take this into account.
Note that many countries have regulations in place regarding acceptable NOx and SOx levels for waste incineration plants, power plants, and so on. If you are retrofitting a CCS solution on an existing power plant, the plant will often already have gas cleaning systems in place. However, further NOₓ and SOₓ removal may still be required depending on the flue-gas composition and the solvent’s tolerance to acidic compounds.
We hope this brief overview has added to your understanding of the challenges involved in ensuring safe and efficient CCS processes, and of the methods available for overcoming those challenges.
