About 3 percent of all carbon emissions are caused by the shipping industry.

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A 240 meter long container ship named Sonin businessman It recently completed testing a carbon capture system on a ship as it cruised around the Persian Gulf. It is one of a small but growing number of ships trying to reduce their climate footprint by capturing and storing their carbon dioxide emissions on board – but finding room for tonnes of CO2 It is a challenge to do.

“You’re miniaturizing a system that was designed for large power plants,” says. Rugia Wayne At Seabound, the UK-based startup behind the test run of the Swann Trader.

Shipping is responsible for about 3 percent of global CO2 emissions. To minimize this, shippers are using Clean fuelLubricate Hulls with bubbles To improve fuel efficiency and even Turning back to the ships. But to reach the near-term options industry covenant Net zero emissions Limited to 2050.

Another possibility is to capture the emissions of ships. Saving them on boardBut it faces major hurdles. One is supplying. Energy to recharge Chemical sorbents are used to absorb CO2. Tristan Smith Some current systems increase fuel consumption by a third to capture half of CO2 emissions, University College London says.

The systems, and the carbon they capture, also take up room on board that would normally be used for valuable cargo. “Space is a problem,” he says. Jasper Ross at TNO, a research organization in the Netherlands. “Especially when you’re talking about a long trip.” Each ton of fuel burned produces about 3 tons of CO2. George Malopas at the Cyprus Marine and Maritime Institute. When it is captured and stored, the extra mass can affect the ship’s stability and reduce its fuel efficiency.

Seabound’s small-scale tests capture about a ton of CO2 per day, Wayne says. That’s a small fraction of the ship’s overall emissions, but she says a full-scale system would capture up to 95 percent of a ship’s CO2.

To save energy, seabound transfers part of its processes to shore. On board, the effluent is looped through a calcium oxide sorbent, which reacts with CO2 to form solid calcium carbonate pebbles. The company then waits to recharge the sorbent until the gravel is unloaded at the port for permanent storage. There is a place for trade. The seabound approach means that a ship must carry sorbent tanks with every ton of CO2 captured. Still, Wynn says the company aims to retrofit 1,000 ships for carbon capture by 2030.

A Dutch company called Value Maritime is taking a similar approach, using a liquid amine sorbent to capture the CO2 and then charge it offshore. Yvette van der Sommen Value Maritime says 26 ships are now using its system as well. Existing Sulfur Pollution-Scrubbers to capture up to 40 percent of the CO2 in the exhaust, although the process has yet to be verified by a third party. She says the company has sold some of the captured CO2 to greenhouses to fertilize plants, but much of it is stored in tanks at ports.

Such systems may now appear attractive to reduce emissions, Smith says. But the rapid scale-up of cleaner shipping fuels could soon make them obsolete – unless they can achieve much higher capture rates at a significantly lower cost. “Shipping has a very short time to decarbonize, because it started so late,” he says.