A new solution for CO2 emissions: Bury them at sea

Ship operators have a radical idea for industrial that are companies searching for ways to dispose of carbon emissions: Take the captured CO out to sea and bury it deep under the ocean floor. But first, supercool the carbon emissions to temperatures so low that they become a liquid.

- Costas Paris

HD Hyundai Heavy Industries, the world's largest shipyard, and Greece-based shipowner Capital Product Partners have designed a specialized vessel to carry liquefied CO. They envision such ships transporting their cargo to depleted offshore oil-and-gas wells, where it would be pumped in and entombed for permanent storage. Capital Product Partners signed a deal for four such ships, to be delivered in 2025 and 2026, that together cost more than $300 million.

"Ships move everything from oil to our furniture, clothes and toothpaste. Now they'll move our emissions, which is in effect waste management," said Jerry Kalogiratos, chief executive of U.S.-listed Capital Product Partners, which operates more than 100 cargo vessels.

The strategy still faces unknowns on its safety and environmental impact, as storing large volumes of CO under the seabed long-term hasn't been tested and research is inconclusive on the effects if it escapes.

In some countries, big corporate emitters must pay taxes for their CO discharges, which they try to minimize by trapping them before they hit the atmosphere. This leaves companies with millions of metric tons of CO that they need to store.

In some areas, inland facilities for storing captured CO, such as depleted oil wells, are gradually running out of room and becoming increasingly expensive, prompting emitters and cargo-ship owners to look for an offshore solution.

A typical voyage of the CO-carrying ship, which will have a reinforced hull and special tanks, would start at a terminal with gas-liquefaction facilities. Cooled to minus 50 degrees Celsius (minus 58 Fahrenheit), carbon dioxide becomes a liquid more than 600 times denser than gas, enabling the transportation of large volumes. The vessels are built to each move up to 25,400 metric tons of CO per trip, according to Capital Product Partners.