by International shipping moves 80% of global trade and accounts for around 3% of the world’s carbon emissions, but is currently not on track to meet its climate targets.
A year ago, the International Maritime Organization — the UN agency that regulates shipping — tightened emissions targets for the shipping industry, aligning it with other industries that aim to achieve net zero emissions by 2050. But they are low emission fuels such as methanol, hydrogen and ammonia. not available fast enough.
Now, Jess Adkins, a chemical oceanographer from the California Institute of Technology (Caltech) thinks he can lend a hand by fitting cargo ships with reactors that can turn the carbon dioxide (CO2) emitted from burning fuel into ocean salt, he says. keep it locked up for 100,000 years.
The process is similar to what is already occurring naturally in the oceans. “This is a reaction the planet has been going on for billions of years,” said Adkins, who founded Calcarea, a startup designing and testing the reactors.
“If we can speed it up, we have a glimpse of a safe and permanent way to store CO2.”
Natural, but faster
Seawater naturally absorbs about a third of the CO2 emitted into the atmosphere, making the water more acidic and dissolving calcium carbonate, which is abundant in the ocean. “Calcium carbonate is the skeleton of corals, shells and all the things that make up most of the sediments at the bottom of the ocean,” Adkins said.
The dissolved calcium carbonate then reacts with the CO2 in the water to form bicarbonate salts, locking the CO2 away. “There are 38,000 gigatons (38 trillion tons) of bicarbonate in the ocean right now,” Adkins added.
Calcarea wants to mimic this natural process by channeling the ship’s exhaust fumes to a reactor in the ship’s hull, where the fumes are vigorously mixed with seawater and limestone – a type of rock made mainly of calcium carbonate, and a common ingredient in concrete. The CO2 in the exhaust fumes reacts with the mixture, creating salty water that locks the CO2 in the form of bicarbonate salts. Adkins says that with a full-scale reactor, he aims to capture and store about half of a ship’s CO2 emissions.
In the natural world, the reaction takes more than 10,000 years, according to Adkins, but in Calcarea’s reactors it takes about a minute, he said. This is achieved by bringing the CO2 and the limestone into close contact with each other.
According to Adkins, the salt water created is released into the ocean, where it poses no threat to marine life or the chemical balance of seawater. He added that the company is looking to add a pre-filter to the system to remove other pollutants from the exhaust that may have mixed into the water, such as particles and unburnt fuel, as well as other contaminants.
After two years of working on the project, in January 2023 he spun off the company from Caltech, where he is still a professor, although he was on leave. He was joined by three co-founders: Caltech undergraduate Melissa Gutierrez, engineer Pierre Forin, and University of Southern California (USC) professor and geochemist Will Berelson.
They raised $3.5 million in funding and focused on the shipping industry. “The beautiful part is that the ship is a natural water pump,” Adkins said, noting that the system requires water to be constantly moving around in order for a reaction to occur between the various elements, which provides movement. ship naturally.
To date, Calcarea has built two prototype reactors, one in the USC parking lot and one in the Port of Los Angeles. In late May, the company announced a partnership with the research and development arm of international shipping company Lomar. Adkins is confident that this will lead to the first full-scale prototype of his reactor to fit on a ship.
The reactors will be adapted to different sizes of ships, including “the largest there is,” the “Newcastlemax” class capable of carrying 180,000 metric tons of cargo. “On one of these we would take up about 4 to 5% of the deadweight tonnage and we would be carrying about 4,000 metric tons of limestone. But we won’t really use all of that,” Adkins said.
Carbon capture at sea
Before Calcarea is ready to install its first reactor, several engineering challenges remain to be resolved. For example, how exactly to fit the reactor on the ship and the logistics of loading the limestone and setting up the supply chain to deliver it. These could be slow steps, according to Adkins.
The cost of the system comes in, according to current estimates, at about $100 per ton of CO2 captured at the exhaust, including the revenue the ship loses by making room for the reactor at the cost of commercial payloads.
Some cargo ships already have similar devices on board, called scrubbers. They are designed to capture and release sulfur emissions — which are harmful to human health and the environment — but not CO2. As of June 2023, they were installed in about 5% of the global merchant fleet, according to the British Ports Association, although studies have found that the wastewater from scrubbers can be “acutely toxic to aquatic organisms.” Calcarea reactors also capture sulfur as part of their CO2 removal process.
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There is also carbon capture technology more similar to Calcarea technology. A British company called Seabound, for example, makes a device that captures between 25% and 95% of a ship’s CO2 emissions. However, it produces solid carbonate pebbles that must be unloaded at a port.
According to Daniel Sigman, a professor of Geological and Geophysical Sciences at Princeton University, who is not affiliated with Calcarea, the company’s approach has a range of advantages over similar strategies being pursued. First, it is the acceleration of a natural process that would happen anyway. Second, because the reaction takes place in an engineering reactor on the ship and does not completely deplete the CO2 supply, it will not increase the acidity levels of the ocean and contribute to the problem of ocean acidification, which is harmful to marine life.
The fact that Calcarea’s founders are experts in the ocean’s carbon cycle, he said, puts them in a good position to avoid the potential pitfalls of CO2 removal: “A lot of other companies looking to improve alkalinity don’t understand oceans the carbon cycle at all relevant scales, and so on. that they are prone to follow an approach that is ineffective – or even counter-productive.”
Adkins believes that Calcarea could help the decarbonisation industry during the transition to greener fuel, and that in the more distant future the reactors could even take the entire space on special vessels, designed to capture the CO2 on land from the atmosphere, as an alternative to storing it underground.
“We think ships will be able to compete with underground CO2 storage,” he said. “Purpose-built ships that collect CO2 and limestone at port, go out to sea and run our reaction – they’ll just be machines to efficiently and safely store carbon in the ocean as bicarbonate.”
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