SeaSequestor could cut costs of carbon capture and storage

An autonomous buoy system that injects liquid CO2 into the seabed could help cut the costs of carbon capture and storage.

Chepstow-based Ocean Resource is developing the SeaSequestor buoy and subsea storage tank as a cheaper alternative to floating manned facilities or installing or upgrading pipelines to transport CO2 captured from power stations.

The 65m-high buoy would allow tankers carrying around 45,000 tonnes of liquid CO2 stored at -55°C to easily transfer their cargo into a tank on the seabed, from where it would gradually be injected into existing oil reserves.

The lower costs of the buoys mean enhanced oil recovery (EOR) – increasing oil production by injecting CO2 into a depleted reserve – could be used in oil fields that would otherwise be considered too small for the process to be cost-effective.

David Bone, chief executive officer at Ocean Resource, told The Engineer he saw EOR as the kick-off market for the SeaSequestors because it created an incentive for investment.

He said: ‘While the technology is being developed, it’s a worthwhile economic benefit that would make people take the risk.’

Ocean Resource uses similar buoys in place of manned floating production units for the oil industry, and to support diesel power generators for remote subsea pumps.

Bone estimates that the buoys save between one-fifth and one-third of the cost of FPSOs (floating production, storage and offloading vessels) and could save a similar amount for CO2 transport, even with a price tag of £40m to £50m per SeaSequestor.

The cost per tonne of CO2 could even be one-tenth of that from building and running a pipe network, he said.

The Technology Strategy Board (TSB) provided around £110,000 to help fund the preliminary engineering work. Now the company is looking for industrial partners to help produce a demonstrator.

Holding the CO2 as a liquid or supercritical fluid will increase the amount that can be transported because it will have a higher density, and perfecting a way to do this is one of the company’s next challenges.

But storing it in tanks on the ocean floor will likely make it easier to maintain the necessary temperature and pressure to keep it in its liquid state.

‘I think it would not be unreasonable to look at a demonstrator within three years’ time,’ said Bone.