County Antrim’s ancient basalt could store more CO₂ than anywhere else in the UK, study finds

Giants Causeway, part of the Antrim Lava Group. (Image: Professor Stuart Gilfillan from our School of GeoSciences at the University of Edinburgh)

Ancient volcanic rocks beneath County Antrim – the same basalt that forms the iconic columns of the Giant’s Causeway – could become a cornerstone of future climate action, with scientists revealing they could permanently store more carbon dioxide than any other site in the UK.

A new study led by the University of Edinburgh has identified eight major underground volcanic formations across the UK capable of storing more than 3,000 million tonnes of CO₂.

According to researchers, this is roughly equivalent to around 45 years of the UK’s industrial emissions.

The research examined the chemistry, thickness and volume of reactive volcanic rocks in County Antrim, the Isle of Skye, and the Lake District, revealing that these ancient formations contain high levels of magnesium and calcium – minerals that naturally bind with carbon dioxide and turn it into solid stone.

Antrim offers the UK’s largest storage potential

Map showing all of the basalt rock areas across UK

Among all the rock groups analysed, the Antrim Lava Group – famous above ground for shaping the Giant’s Causeway’s 60-million-year-old hexagonal pillars – was found to have the greatest capacity, with a mid-range estimate of 1,400 million tonnes of CO₂.

By comparison, the Borrowdale Volcanic Group in northern England could store 700 million tonnes, while the Skye Lava Group in Scotland was estimated at around 600 million tonnes.

If even a portion of this storage potential is proven viable, it could play a major role in helping the UK meet its legally binding climate targets.

How turning CO₂ into stone works

The process, known as carbon mineralisation, involves dissolving captured CO₂ in water before injecting it into porous volcanic rocks deep underground. There, the mineral-rich basalt triggers a natural chemical reaction, binding the CO₂ into a stable carbonate mineral – effectively turning it to stone.

The method has already been demonstrated to work rapidly and safely in pilot projects in Iceland and the United States, offering what scientists call a secure, permanent storage solution for otherwise unavoidable industrial emissions.

Researchers highlight “practical and permanent” climate tool

Angus Montgomery, who began the study while completing his BSc in Geology and Physical Geography at the University of Edinburgh, said:

“By showing where the UK’s most reactive volcanic rocks are and how much CO₂ they could lock away, we highlight a practical and permanent way to mitigate unavoidable industrial emissions, adding to the UK’s arsenal of decarbonisation options”.

Professor Stuart Gilfillan, Personal Chair of Geochemistry at the University of Edinburgh and the study lead, added:

“To cut CO2 emissions at scale, we urgently need carbon storage. CO2 mineralisation offers the UK more room to store CO2, adding to the huge resource offered by the rocks beneath the North Sea.

“Our next steps are to assess effective porosity and rock reactivity in detail. This will tell us how efficiently each formation can mineralise CO2 in practice.”

A volcanic past shaping a low-carbon future?

The findings, published in Earth Science, Systems and Society, issued by the Geological Society of London and funded by the National Environment Research Council (NERC), provide the clearest picture yet of how Britain’s volcanic history could support future climate solutions.

In County Antrim, where flows of ancient lava once shaped the coastline’s distinctive black basalt cliffs, researchers say geology could once again play a defining role – this time in helping limit global temperature rise to between 1.5°C and 2°C, in line with international climate goals.