Carbon Capture and Storage 101

How CCS Works

At its core, CCS is a three-step process: capture, transport, and storage. The process begins at where CO2 concentrations are the highest coal or gas power plants, cement and steel factories. Beside capturing CO2 directly from industrial smokestacks, there is also a way to pull carbon straight out of the atmosphere. This approach is called. Direct Air Capture (DAC) and it targets the much lower concentrations of CO2 found in the atmosphere. Compared to CO2 capturing process taking place at plants etc., DAC requires more energy due to the dilute air and ends up being much more costly.Unlike conventional CCS, which focuses on preventing new emissions, DAC has a remarkable potential to remove the carbon we’ve already released over centuries. By this way we will not just slow down future emissions but also reverse the past damage.

Conventional approaches rely on the employment of liquid solvents such as amines to scrub flue gases; binding CO2 molecules before they escape through smokestacks. Although this approach works well, it requires a lot of energy input. To enhance efficiency, next-generation technologies such as solid sorbents, membranes and most importantly MOFs are being developed. MOFs are highly porous materials consist of metal ions connected by organic linkers forming sponge-like structures. They have an enormous surface area- sometimes reaching thousands of square meters per gram- with countless active sites where CO2 molecules can be adsorbed and held.What makes MOFs special is their tunable structure: by adjusting their chemical composition and pore size, they can be easily tailored to selectively capture CO2. By this way the overall cost and the amount of energy needed throughout the whole process is reduced.

Transport

After being captured, CO2 is compressed into a dense liquid-like form. This phase transformation makes it much easier to move CO2 in large volumes, typically using pipelines. The advantage of using pipelines is that this infrastructure is already extensively used by the oil and gas industry so it is well-established and requiring little new technology to adapt for CO2 transport.Also the risk associated with CO2 are lower than those of oil or natural gas pipelines: since CO2 is neither flammable nor explosive its transport via pipelines is much more safer and easier to manage.

Storage

The final step in the CCS chain is the long-term storage of captured CO2. Once compressed and transported, CO2 is injected deep underground. The depth is typically 800 meters below the surface where depleted oil and gas reservoirs are loccated. These geological formations act like natural containers: while their rocks layer have a porous strcuture which allos them to absorb CO2 the impermeable caprock layers above them lock CO2 securely in place not letting any of it to ooze back into the atmosphere. The Sleipner porject in Norway already proved that this can be done safely: since 1996, about one million tons of CO2 per year is being stored in a saline aquafier.Shell Canada’s Quest project has captured and stored over six million tons since 2015.Both sites are closely monitored using seismic surveys and pressure measurements to ensure no leakage.

State-of-art

CCS has come a long way from being a “future idea” to a real, working technology with hundreds of projects in motion. There are over 700 projects in development, capturing and storing more than 50 million tons of CO2 annually which equals roughly the emissions of a small country like Greece or Peru.The momentum is exciting, but we’re still only halfway to where we need to be for a net-zero future. The takeaway? CCS is here, it works, and it’s scalable. To truly close the gap however, we need faster investment, stronger policy support, and a push to move from announcements to action. Join us in our next blog where we dive deeper into the role of MOFs in CCS.