New paper shows potential for safe storage of carbon dioxide offshore

A world-first study led by the National Oceanography Centre (NOC) following research off the coast of Scotland suggests that storing carbon dioxide (CO₂) under the sea in a process known as carbon capture and storage (CCS) is both viable and safe.

In the unlikely event of unintended CO₂ emissions from a storage reservoir, the work demonstrated that these are detectable and quantifiable through new technologies.

Scientists conducted an experiment in the North Sea 130km northeast of Aberdeen where they simulated a release of CO₂ over a period of 12 days at a depth of 120 metres and three metres below the seabed, to test whether new technologies were able to detect even small releases of CO₂. The new methodology also allowed the project scientists to measure how much was released and where it was being released from.

Carbon capture and storage is regarded as one of the more effective tools in the fight against climate change. The process involves separating the CO₂ generated during the industrial process such as power plants, hydrogen and ammonia production and steel plants, then transporting the gas through pipes, in tankers via roads or ships and finally injecting the CO2 directly into rock formations or depleted oil and gas reservoirs deep underground.

The ground-breaking pilot study will help inform the direction of technology development for the long-term monitoring of offshore CO2 storage reservoirs and is a huge step forward in assuring regulators that this process is safe by being able to monitor any potential leaks as well as assess any potential damage to marine life. The work is already being used to inform the operators of two proposed storage projects, one in Denmark and another in the UK.

Professor Douglas Connelly, Lead Author and Associate Director, Science and Technology at the National Oceanography Centre, said: “Carbon capture and storage is a key mitigation strategy for keeping the global temperature rise below 1.5°C and offshore storage can provide up to 13% of the global CO₂ reduction target. The artificial CO₂ release in our study enabled us to detect any emissions to the marine environment using acoustic, chemical and physical approaches as well as identifying the location of any leaks – something not previously achieved.

“Showing that carbon capture and storage is safe, as well as being able to monitor any unintended emissions of CO₂, is a crucial step towards much larger implementation of this technology. We have combined existing off-the-shelf technology with the NOC’s new sensors, methodological approaches and state-of-the-art modelling work, taking a major step forward in assuring that offshore CO2 storage is safe. This report will help inform both the public and the regulators that this is a safe process and in doing so, providing regulators and governments the tools they need to effectively regulate the conformity of future storage facilities.”

Professor Jonathan Bull at the University of Southampton, and acoustics lead in the project said “we have demonstrated that very small quantities of CO₂ can be detected and quantified using passive and active acoustic techniques, including systems mounted on autonomous underwater vehicles”.

Jerry Blackford, Head of Marine Systems Modelling at Plymouth Marine Laboratory and a work package leader in the project said: “The observations and sensor development, coupled with our state-of-the-art digital modelling capabilities now allow us to develop demonstrably effective and cost -efficient monitoring strategies for offshore CCS.”

The paper, Assuring the integrity of offshore carbon dioxide storage, has been published on ScienceDirect.

The project, Strategies for the Environmental Monitoring of Marine Carbon Capture and Storage – STEMM-CCS, was funded by the European Union’s Horizon 2020 research and innovation programme under the grant agreement number 654462. A special issue comprises detailed results of the project.