International shipping movements 80% of global trade and accounts for about 3% of the world’s carbon emissions, but right now, it is not on the course to meet its climate goals.
A year ago, the International Maritime Organization — the UN agency that regulates shipping — has tightened emissions targets for the shipping industry, bringing it in line with other industries that aim to achieve net-zero emissions by 2050. But low-emissions fuels like methanol, hydrogen and ammonia are not become available fast enough.
Now, Jess Adkins, a chemical oceanographer at the California Institute of Technology (Caltech), thinks he can help by equipping cargo ships with reactors capable of transforming the carbon dioxide (CO2) emitted by burning fuel into ocean salts, which he says him, keep him locked away for 100,000 years.
The process is similar to what already happens naturally in the oceans. “This is a reaction that the planet has been going through for billions of years,” said Adkins, who founded Calcarea, a startup that is designing and testing the reactors.
“If we can accelerate, we have the opportunity to find a safe and permanent way to store CO2.”
Natural, but faster
Sea water naturally absorbs about a third of CO2 emitted into the atmosphere, making the water more acidic and causing it to dissolve calcium carbonate, which is abundant in the ocean. “Calcium carbonate is the raw material for coral skeletons and shells and all the things that make up most of the sediments on the ocean floor,” Adkins said.
The dissolved calcium carbonate then reacts with the CO2 in the water to form bicarbonate salts, locking in the CO2. “There are already 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 gases into a reactor in the ship’s hull, where the vapors are vigorously mixed with seawater and limestone — a type of rock made primarily of calcium carbonate and a common ingredient in concrete. . The CO2 in the exhaust reacts with the mixture, creating salt water that traps the CO2 in the form of bicarbonate salts. Adkins says that with a large-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 the Calcarea reactors it takes about a minute, he said. This is achieved by placing the CO2 and limestone in intimate contact with each other.
The saltwater created is simply released into the ocean, where it poses no threat to marine life or the chemical balance of seawater, according to Adkins. He added that the company is also considering adding a pre-filter to the system to eliminate other exhaust pollutants that could mix with water, such as particulates and unburned fuel, as well as other contaminants.
After two years of work on the project, in January 2023 he separated the company from Caltech, where he is still a professor, although away. He was joined by three co-founders: Caltech student 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,” said Adkins, remembering that the system requires the water to be in constant movement for the reaction between the various elements to occur, something that is provided naturally by the movement of the ship. ship.
To date, Calcarea has built two prototype reactors, one in the USC parking lot and the other in the Port of Los Angeles. At the end of May, the company announced a partnership with the research and development arm of international shipping company Lomar. Adkins is confident this will lead to the first full-scale prototype of his reactor to be installed on a ship.
The reactors will be adapted to different sizes of ships, including “the largest there are”, the “Newcastlemax” class, capable of carrying 180 thousand metric tons of cargo. “In one of them, we would take about 4 to 5% of the deadweight tonnage and load about 4,000 metric tons of limestone. But we’re not actually going to use all of it,” Adkins said.
Carbon capture at sea
Before Calcarea is ready to install its first reactor, there are still some engineering challenges to be resolved. For example, how exactly to fit the reactor onto the ship and the logistics of loading the limestone and setting up the supply chain to deliver it. These may be slow steps, warns Adkins.
The cost of the system, according to current estimates, amounts to around 100 dollars per ton of CO2 captured in the exhaust, which includes the revenue that the ship loses when creating space for the reactor at the expense of the commercial payload.
Some cargo ships already have similar devices on board, called purifiers. They are designed to capture and discharge sulfur emissions — harmful to human health and the environment — but not CO2. In June 2023, they were installed in around 5% of the global merchant fleet, according to the British Port Association, although studies have found that wastewater from purifiers can be “acutely toxic to aquatic organisms”. The Calcarea reactors also capture sulfur as part of the CO2 removal process.
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There is also carbon capture technology more directly similar to Calcarea’s. A British company called Towards the sea, for example, manufactures 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 involved with Calcarea, the company’s approach has a number of advantages over similar strategies being pursued. First, it is the acceleration of a natural process that would occur anyway. Secondly, as the reaction takes place in a reactor designed on the ship and does not completely consume the CO2 supply, it will not increase ocean acidity levels and will not contribute to the problem of ocean acidification, which is harmful to marine life.
Because Calcarea’s founders are experts in the ocean carbon cycle, he added, this makes them well-positioned to avoid potential pitfalls of CO2 removal: “Many other companies looking to improve ocean alkalinity don’t understand the carbon cycle at all.” the relevant scales and are therefore prone to adopting approaches that are ineffective – or even counterproductive.”
Adkins believes that Calcarea could help industry decarbonize during the transition to greener fuels and that, in the more distant future, reactors could even take up all the space on special ships designed to lock CO2 that has been captured on land from the atmosphere. , as an alternative to underground storage.
“We believe ships will actually be able to compete with underground CO2 storage,” he said. “Purpose-built ships that collect CO2 and limestone in a port, go out to sea and just control our reaction – they will just be machines to efficiently and safely store carbon in the ocean as bicarbonate.”
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