CO2 leaks: engineers join forces to understand the threat posed by greater use of CCS

ENGINEERING consultancy Ricardo has joined a partnership investigating what would happen if a large pipeline carrying captured CO2 were to fail. Known as Project Skylark, the research will help emergency responders prepare for leaks, and improve models used by industry.

Skylark is a three-year project led by DNV and involving the UK government’s Health and Safety Executive Science Division, the UK National Centre for Atmospheric Science, the US University of Arkansas, and now Ricardo. It has been launched in response to the increase in carbon capture and storage (CCS) projects that are being backed to decarbonise heavy industry.

What could happen when concentrated CO2 escapes?

The Skylark partners note that while CO2 is already transported by pipeline at scale today, the use of CCS will lead to significant increases in the volumes carried through networks of onshore and offshore pipelines.

An article published in IChemE’s Loss Prevention Bulletin has outlined numerous hazards posed by CO2 during CCS operations. CO2 can cause pipeline corrosion, while a sudden depressurisation caused by a leak could result in a boiling liquid expanding vapour explosion (BLEVE). A leak of CO2 into the environment poses a significant threat to those who inhale it.

An assessment by the UK’s Health & Safety Executive (HSE) notes that a person will be killed if they inhale CO2 at a concentration above 50%. The concentration of CO2 being transported through CCS pipeline networks would be much higher than this, likely in excess of 95%.

Because CO2 is heavier than air, a leak could see it collect in valleys and low-lying ground and asphyxiate those caught up in its cloud.

Notable CO2 leaks

The HSE notes it is important to bear in mind the risk posed by any CO2 release is very dependent on the source of the release, the amount released, the topography of the surroundings and the weather conditions.

One of the largest and most notable leaks of CO2 occurred in 1986 in Cameroon – not from a pipeline or industrial operation but from a lake. A magma chamber underneath Lake Nyos released 1.6m t of CO2 which killed more than 1,700 people, thousands of livestock, and destroyed trees and vegetation around the lake.

In 2008, 15 t of CO2 released from a fire-extinguishing installation in Mönchengladbach in Germany spread outside into the still air intoxicating 107 people, 19 of whom were hospitalised.

In 2020, a leak of CO2 from a pipeline operated by Denbury in the US hospitalised 45 people and led to the evacuation of residents from the nearby town of Satartia. An investigation by authorities found that the pipeline has been ruptured by a landslide following heavy rains and the cloud of CO2 dissipated slowly because of local weather conditions and the contours of the surrounding land. It ordered new measures to protect the public, calling on pipeline operators to better understand how their infrastructure might be under threat from climate change.

Craig Thomson, chemical lead for Ricardo, said: “Although failure in these networks is extremely rare, by building a greater understanding of the implications of a release incident we will be helping the sector to refine and improve its emergency response plans.”

What is Project Skylark looking to do?

Skylark is focused on four challenges. The first is understanding the interaction between pipeline failure, crater formation and atmospheric conditions to predict how CO2 disperses. The second is how terrain including slopes and valleys influences the behaviour of a dense vapour cloud produced by a CO2 pipeline leak.

The third is focused on emergency response and will test the equipment, techniques, and procedures used by emergency responders in large CO2 releases, including search and rescue operations and the impact on internal combustion engines. The final challenge will investigate how to vent CO2 from pipelines. This will involve studying the outflow rates, vent heights, and hazard distances associated with necessary venting events, ensuring safe dispersion of gas without compromising the integrity of a pipeline.