What is CCS?

Carbon Capture and Storage (CCS) involves capturing the CO₂ emitted by large plants and storing it permanently underground.

We turn carbon dioxide into an opportunity

Carbon dioxide can be captured directly from industrial chimneys and either reused in subsequent production processes or permanently stored deep underground to prevent its release into the atmosphere. This suite of techniques is known as Carbon Capture Utilization and Storage (CCUS), an acronym which includes both Carbon Capture and Utilization (CCU) and Carbon Capture and Storage (CCS). In addition to supporting decarbonization, both these strategies offer the advantage of turning the climate change challenge into an economic asset, potentially opening up new avenues for growth and job creation. They are particularly useful for the “hard-to-abate” sectors, i.e. energy-intensive industries where, due to their high energy demand and specific operating characteristics, there are currently no viable technological alternatives that can reduce emissions in an efficient and cost-effective way.
Examples of hard-to-abate sectors include steel, cement, paper and chemicals.


CCU and CCS: differences and similarities

Both carbon capture and utilization (CCU) and carbon capture and storage (CCS) start with a capture stage where carbon dioxide is extracted directly from the chimneys of large industrial plants and isolated from other gases it is mixed with. Once captured, the CO₂ is compressed to facilitate transport, typically by pipeline, or alternatively by sea or road. At this point we have purified, concentrated carbon dioxide, which can be reused other industrial processes as “raw material” or permanently stored deep underground. The former process is known as CCU and the latter as CCS. One application of CCU is the mineralisation of CO2 with natural mineral phases, with the resulting compounds used in cement production. CCS, on the other hand, involves injecting CO₂ into deep geological formations, such as depleted hydrocarbon fields or saline aquifers, selected after detailed geological and technical assessments. Using these depleted fields offers significant advantages, as it allows us to use well-known geological structures, allowing accurate predictions to be made about the distribution of CO₂ within them. In addition, reusing existing infrastructure makes it possible to create fast-track, low-cost projects, applying circular economy principles to decarbonization. The methodologies underpinning CCS are reliable and mature, based on lessons learned from underground natural gas storage - a technique Italy has been using for its strategic reserves since 1964, in compliance with the highest safety standards.

Underground storage: ensuring process integrity and safety

CCS projects are based on proven, reliable technologies, drawing on Italy's extensive experience in underground natural gas storage - a field in which Italy has been a pioneer since the 1960s. Every operation in the Ravenna CCS project will benefit from a comprehensive monitoring framework already in place in Ravenna, which has previously been used for extraction operations.

Advantages of re-using depleted natural gas fields

In CCS plants, carbon dioxide extracted from industrial chimneys is compressed and injected into deep geological formations suitable for its storage, where it is trapped underground indefinitely.


Depleted hydrocarbon fields, such as those that have been chosen for the Ravenna CCS project, are much less pressurised because they have been previously exploited for energy-related purposes. As the carbon dioxide is gradually injected into these fields, the pressure approaches the original state and the processes are completed before this level is reached.  This type of storage is safe and permanent because these fields are totally impermeable, and proof of this is the fact that they were able to hold large quantities of natural gas for millions of years without escape routes. From a scientific perspective, CO₂ is essentially the carbon content of the natural gas that was extracted and then burned. CCS therefore essentially “puts the carbon back in its place”, returning it to its original reservoir in the geosphere.


There are four mechanisms that ensure that carbon dioxide remains in the reservoir:

  • physical trapping: since it is less dense than water, CO₂ tends to rise within the reservoir, only to be trapped under an impermeable overlay.
  • capillary trapping: as carbon dioxide penetrates through the interstices of the rock, it is trapped by capillary forces that prevent it from continuing its movement.
  • solubilisation: a fraction of the CO₂ mixes with the geological water in the field and dissolves in it.
  • mineralisation: by reacting slowly with some minerals in the rocks, CO₂ precipitates in the form of carbonates and is permanently transformed into minerals.

The first capture mechanism takes place immediately after injection, while the other three work at different times and over the years the CO₂ remains trapped underground, resulting in a state of permanent storage. A study titled "Zero Carbon Technology Roadmap", carried out by the European House Ambrosetti in 2023, showed that for well-managed CCS sites, over 99% of the CO2 will remain safely stored for at least 500 years.


CCS builds on more than a century of expertise in natural gas storage

The process of capturing and storing carbon dioxide is safe and technically mature. It uses proven, commercially available capture technologies and draws on the expertise gained from over a century of natural gas storage.  Since the 1960s, Italy has been using depleted gas fields to store strategic gas reserves. It has 14 active sites with a working capacity of over 14 billion m3 and there haven't been any major incidents (source: Italian Ministry of Economic Development).  Globally, CCS initiatives have been in operation for years, for instance Snohvit (since 2008) and Sleipner (since 1996) in Norway, and no CO₂ leakage has been reported.