Carbon capture is the process of trapping carbon dioxide (CO2) before it enters the atmosphere or removing it after it is already there. The captured CO2 is then either stored permanently underground (carbon capture and storage, or CCS) or used in industrial processes (carbon capture and utilisation, or CCU). The combined term CCUS covers all three approaches.
Think of it like fitting a filter to an exhaust pipe. Instead of letting CO2 pour out of a power station chimney or cement factory and into the atmosphere, capture technology intercepts it and diverts it somewhere it cannot contribute to warming. The idea is not to replace emissions reduction but to deal with emissions that are extremely difficult or impossible to eliminate any other way.
🔬 How Does Carbon Capture Work?
There are three main approaches to capturing CO2, depending on where and when it is intercepted.
🏭 Post-Combustion Capture
This is the most common method. CO2 is separated from the exhaust gases (flue gas) after fossil fuels or biomass have been burned. The most commercially proven technology uses chemical solvents – typically amines – to absorb CO2 from the flue gas. The solvent is then heated to release the concentrated CO2 for transport and storage. This approach can be retrofitted to existing industrial facilities like power stations and cement plants.
⚙️ Pre-Combustion Capture
Here, the fuel is converted into a mixture of hydrogen and CO2 before combustion. The CO2 is separated and captured, and the hydrogen is burned as a clean fuel. This approach is used in some industrial hydrogen production processes and integrated gasification combined cycle (IGCC) power plants.
🌬️ Direct Air Capture (DAC)
Instead of capturing CO2 at the source, DAC pulls it directly out of the ambient air using chemical processes. Because CO2 is far more diluted in open air (about 420 parts per million) than in industrial exhaust (where it can be 10-30%), DAC requires significantly more energy and is currently much more expensive. However, it has the advantage of being able to operate anywhere and can address emissions that have already been released – making it a potential tool for achieving negative emissions.
📦 What Happens to the Captured CO2?
🪨 Geological Storage (CCS)
The captured CO2 is compressed into a liquid-like state and injected deep underground into geological formations – typically depleted oil or gas fields, deep saline aquifers (porous rock formations filled with salt water) or unmineable coal seams. The CO2 is trapped by impermeable cap rock above the storage formation, preventing it from escaping back to the surface. In some cases, injected CO2 can react with minerals in the rock and solidify permanently over time.
♻️ Utilisation (CCU)
Alternatively, captured CO2 can be used as a raw material in industrial processes – for example in producing synthetic fuels, building materials, chemicals or carbonated drinks. However, most utilisation pathways eventually release the CO2 back into the atmosphere (when the fuel is burned, for example), so the climate benefit is limited unless the CO2 is permanently locked into a product like concrete.
🌱 BECCS (Bioenergy with CCS)
BECCS combines biomass energy with carbon capture. Plants absorb CO2 as they grow. When that biomass is burned for energy and the resulting CO2 is captured and stored underground, the net effect is removal of CO2 from the atmosphere – achieving what are called “negative emissions.” BECCS is considered a key technology in many climate models for reaching net zero.
🇮🇪 Carbon Capture in Ireland
Ireland’s position on carbon capture is complicated. The technology is referenced in the Climate Action Plan as a potential tool for decarbonising hard-to-abate sectors, but practical deployment faces significant legal and infrastructure barriers.
🚫 Legal Restrictions
At present, storing CO2 in geological formations is not permitted under Irish law. Ireland has not yet transposed the EU CCS Directive (2009/31/EC) to allow geological storage, and has not ratified the amendment to the London Protocol that would allow international transport of CO2 for offshore storage. These restrictions effectively block both domestic CCS projects and the export of captured CO2 to storage sites in other countries like Norway or the Netherlands, where commercial operations are already underway.
A CCUS Task Force has been developing a workplan to progress a regulatory framework for industrial carbon management in Ireland, and recommendations on addressing the 26 MtCO2eq gap in the second carbon budget period (2026-2030) were expected in 2025. But until the legal framework changes, no commercial CCS project can operate in Ireland.
🗺️ Storage Potential
Despite the legal barriers, Ireland has significant geological storage potential. The two most promising sites are both offshore depleted gas fields. The Kinsale Head gas field off the coast of Cork has a provisional estimated storage capacity of 321 Mt of CO2 – enough to store roughly 40 years of emissions from Ireland’s ten largest point-source emitters. The Corrib gas field off the coast of Mayo has an estimated capacity of 44 Mt and existing pipeline infrastructure that could potentially be repurposed for CO2 transport when the field’s natural gas production ceases (expected around 2030-2035).
Beyond depleted gas fields, theoretical storage potential exists in saline aquifers in the Celtic Sea and other offshore basins, with some studies suggesting total capacity in the tens of gigatonnes – though these estimates need much more geological characterisation before they could be considered viable.
🏗️ Industrial Need
Ireland’s cement sector is the most obvious candidate for CCS. Cement production generates process emissions from the chemical reaction that converts limestone to clinite – emissions that cannot be eliminated simply by switching to renewable energy. SEAI research identifies cement sites and energy-from-waste facilities as the most suitable locations for CCS and BECCS in Ireland, with potential to achieve approximately 1 MtCO2 per year of negative emissions in high-deployment scenarios.
⚖️ The Debate Around Carbon Capture
Carbon capture is one of the most contested topics in climate policy. Supporters argue it is essential for reaching net zero because some industrial emissions (cement, steel, chemicals) cannot be eliminated by other means, and negative emission technologies like BECCS and DAC are needed to offset residual emissions. The IPCC includes CCS in the majority of its modelled pathways for limiting warming to 1.5°C.
Critics raise several concerns. CCS is expensive – current costs range from roughly €50-120 per tonne of CO2 for industrial point-source capture, and €200-600+ per tonne for direct air capture. There is a risk that promoting CCS gives fossil fuel industries a justification to continue operating rather than transitioning to clean alternatives. There are also questions about long-term storage security – whether stored CO2 could leak over centuries – though evidence from existing projects suggests well-chosen geological sites can store CO2 permanently.
In the Irish context, the practical argument is straightforward: Ireland is projected to exceed its carbon budgets by a significant margin, and the Climate Action Plan has identified a 26 MtCO2eq gap in the second budget period that needs to be closed. CCS and carbon removal technologies are being considered as part of the solution – but only if the legal and infrastructure barriers can be resolved in time.
🔗 How Carbon Capture Connects to Other Climate Terms
- 🌿 Net zero – CCS and negative emission technologies are considered essential for offsetting residual emissions that cannot be eliminated
- 🌿 Carbon budgets – CCS could help close the gap between Ireland’s projected emissions and its legally binding budget limits
- 🌿 Carbon footprint – CCS at industrial scale reduces the embedded carbon in products like cement and steel
- 🌿 Scope 1 emissions – CCS targets direct emissions from industrial processes that renewable energy alone cannot eliminate
- 🌿 Greenhouse gases – CCS specifically targets CO2, the most abundant and long-lived greenhouse gas
- 🌿 Renewable energy – CCS is not a replacement for renewables but a complement for sectors where electrification is not feasible
❓ Frequently Asked Questions
Is carbon capture the same as carbon offsetting?
No. Carbon capture physically removes CO2 from industrial exhaust or the atmosphere and stores it permanently underground. Carbon offsetting involves paying for emission reductions or removals elsewhere (such as tree planting or renewable energy projects) to compensate for your own emissions. CCS produces a direct, measurable, permanent removal. Offsetting quality varies enormously depending on the scheme.
Can Ireland store CO2 underground?
Not yet. Geological storage of CO2 is currently not permitted under Irish law. However, Ireland has significant potential storage capacity in depleted offshore gas fields – the Kinsale Head field alone could store an estimated 321 Mt. Legal and regulatory changes would be needed before any storage project could proceed.
Is carbon capture proven technology?
Yes, at an engineering level. Several commercial CCS projects operate globally, including the Northern Lights project in Norway which became Europe’s first fully operational CCS value chain in 2025. The challenge is scaling up deployment, reducing costs and building the necessary transport and storage infrastructure. In Ireland specifically, infrastructure is at an early stage of development.
Why not just plant more trees instead of using CCS?
Afforestation and reforestation are valuable, but they have limits. Trees take decades to reach full carbon absorption capacity, require large land areas, and can release stored carbon if they burn, die or are harvested. CCS can store millions of tonnes per year in a permanent geological formation. Most climate models suggest both approaches are needed – neither alone is sufficient to reach net zero.