Over 80% of global trade goods are transported by sea, and maritime transport ships account for approximately 3% of the world’s carbon emissions. A startup in the United States has discovered a method to convert CO2 emitted by ships into salt.
One year ago, the International Maritime Organization (IMO) tightened emission targets for maritime transport to align with other industries, aiming for net-zero emissions by 2050. However, low-emission fuel alternatives such as methanol, hydrogen, and ammonia are not readily available.
A cargo ship passing through the Suez Canal in Ismailia, Egypt on January 13. (Photo: THX/TTXVN)
In light of this reality, chemical oceanographer Jess Adkins from the California Institute of Technology (Caltech) believes he can help the shipping industry reduce emissions by equipping cargo ships with reactors capable of converting carbon dioxide (CO2) emitted from fuel combustion into seawater salt.
This process mimics what occurs naturally in the oceans. Seawater absorbs about one-third of the CO2 released into the atmosphere, increasing its acidity and dissolving calcium carbonate, a substance abundant in the oceans. Adkins stated, “Calcium carbonate is a key component of coral skeletons, shells, and all the materials that constitute a large part of ocean floor sediments.” Afterward, the dissolved calcium carbonate reacts with CO2 in the water to form bicarbonate salt, effectively locking in CO2. Currently, there are 38 trillion tons of bicarbonate in the oceans.
Adkins has founded a startup called Calcarea, which is designing and testing reactors that convert CO2 into bicarbonate salt. According to him, this reaction has been occurring for billions of years on the planet: “If we can accelerate this process, we have a chance to find a safe and long-term way to store CO2.”
Calcarea simulates this natural process by channeling ship emissions into a reactor installed within the vessel. There, the emissions are combined with seawater and limestone – a rock primarily composed of calcium carbonate. The CO2 in the emissions reacts with this mixture, generating brine that securely traps CO2 in the form of bicarbonate salt.
Adkins noted that the goal is to create a large-scale reactor capable of capturing and storing approximately half of a ship’s CO2 emissions.
In nature, the reaction takes over 10,000 years, but with Calcarea’s reactors, the time is reduced to around one minute. This reduction is achieved by ensuring close contact between CO2 and limestone. According to Adkins, the brine produced by Calcarea’s reactor is discharged into the ocean without threatening marine life or the chemical balance of seawater.
He explained, “The great thing is that the ship itself acts as a natural water pump.” He also emphasized that this system requires water to continuously flow to facilitate reactions between different elements, and the ship’s movement will aid this process.
He revealed that the company is also considering adding a preliminary filter to the system to remove other pollutants from the emissions that may mix with the water, such as particulates and unburned fuel.
After two years of investment in the project, in January 2023, he spun off Calcarea from Caltech. Along with three co-founders, Melissa Gutierrez, a Caltech student, engineer Pierre Forin, and Professor Will Berelson from the University of Southern California (USC), they raised $3.5 million in funding and focused on the maritime industry.
To date, Calcarea has developed two prototype reactors, one located in the USC parking lot and another in the Port of Los Angeles. By the end of May, Calcarea announced a partnership with international shipping company Lomar. Adkins is confident that this will help install the first reactor prototypes on ships. The reactors will be custom-designed for various ship sizes.
A cargo ship passing through the Suez Canal on January 13. (Photo: THX/TTXVN).
Before Calcarea is ready to install its first reactor, there are still several technical challenges to address, such as ensuring the reactor fits snugly within the ship and transporting limestone.
The estimated cost of the system is around $100 per ton of CO2 captured from emissions, including the revenue lost by the ship due to space taken up by the reactor.
Some cargo ships have already been equipped with similar onboard systems to capture and discharge sulfur gases that are harmful to human health and the environment. According to the UK Port Authority, as of June 2023, these systems have been installed on about 5% of global commercial shipping vessels. However, studies have found that wastewater from these filtration devices can be “toxic to marine organisms.” Meanwhile, Calcarea’s reactors also capture sulfur in their CO2 removal process.
According to Professor Daniel Sigman at Princeton University, who is not affiliated with Calcarea, the company’s approach has several advantages. First, it accelerates a natural process.
Second, because the reaction occurs onboard and does not completely consume the CO2 source, it will not increase ocean acidity and will not contribute to ocean acidification, which is harmful to marine life. The oceans produce 50% of the oxygen we need. They also absorb 25% of carbon dioxide emissions and capture 90% of the excess heat generated by these emissions. The oceans are often referred to as the “largest carbon reservoir” on the planet – a crucial buffer against the impacts of climate change.
Sigman noted that because the founders of Calcarea are experts in the ocean’s carbon cycle, they can avoid potential pitfalls associated with CO2 removal.
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