In a groundbreaking development that could revolutionize efforts to decarbonize one of the world’s most challenging industries, researchers from the University of Southern California (USC) and the California Institute of Technology (Caltech) have engineered a pioneering shipboard system designed to capture and convert carbon dioxide emissions from maritime vessels into a harmless oceanic compound. This advancement offers the potential to cut up to 50% of CO2 emissions generated by global shipping—an industry responsible for nearly three percent of total greenhouse gas emissions—without the need for expensive retrofits or radical changes to vessel design.
The innovative system, borne from years of collaborative scientific research and now being commercialized through the startup Calcarea, ingeniously accelerates a natural oceanic chemical process already responsible for buffering carbon dioxide in marine environments. The process draws from a well-understood geochemical phenomenon: as carbon dioxide dissolves in seawater, it reacts with minerals like limestone, neutralizing acidity and converting CO2 into stable bicarbonate ions. By replicating and amplifying this reaction onboard ships, the new technology promises to transform problematic greenhouse gas emissions into a benign, ocean-safe solution.
Lead researcher William Berelson, a professor of Coastal and Marine Systems at USC, describes the system’s elegance: “We’re harnessing and speeding up the ocean’s own buffering mechanism but doing it at the scale and speed necessary to impact emissions from moving vessels.” The science is deceptively simple yet profoundly impactful. When ocean water is pumped aboard a ship, CO2 from exhaust gases dissolves into the seawater, slightly acidifying it. Passing this acidified water through a limestone bed triggers a chemical reaction that converts dissolved CO2 into bicarbonate ions. These ions, naturally abundant in seawater, pose no environmental risk. After treatment, the water is released back into the ocean, effectively sequestering carbon dioxide without harmful side effects.
The system’s foundation lies in fundamental chemistry, invoking the principles of acid-base reactions and carbonate equilibria. Carbon dioxide, when absorbed into water, forms carbonic acid, lowering the pH. In turn, this acid reacts with alkaline minerals, such as calcium carbonate in limestone, leading to the formation of bicarbonate ions and releasing calcium ions. This reaction not only neutralizes acidity but permanently traps carbon within a stable ionic form that prevents its immediate return to the atmosphere, thus serving as a carbon sink.
Testing in controlled laboratory conditions confirmed researchers’ theoretical models, showing that precise quantities of seawater, limestone, and CO2 could be managed to drive the reactions efficiently. These promising lab results provided the confidence to scale the technology conceptually, adapting it to the complexities of an operational vessel. Sophisticated computational modeling simulated the long-term impacts of repeated operation on ocean chemistry, particularly focusing on a hypothetical trans-Pacific route between China and Los Angeles sailed over a decade. These models indicated negligible downstream changes in seawater pH or composition, assuring the environmental safety and sustainability of the approach.
Despite the shipping industry’s persistent struggle with decarbonization due to logistical challenges and long-distance voyage requirements, this shipboard carbon capture technology offers an economically viable complement to existing methods such as low-carbon fuels and electrification. Jess Adkins, co-founder and CEO of Calcarea and professor at Caltech, emphasized the system’s compatibility with current shipping infrastructure: “Our design integrates seamlessly with existing vessels, requiring minimal modifications, enabling swift and wide adoption. It’s engineered for scalability, aligning with fleetwide implementation rather than isolated applications.”
From a technological perspective, the core components include seawater intake systems, limestone reaction chambers, and exhaust gas capture units. The system must balance seawater flow rates, CO2 absorption efficiency, and mineral reaction kinetics to maintain operational stability and maximize carbon capture performance. Researchers continue to refine reaction rate constants and mineral consumption parameters, seeking to optimize the durability and maintenance demands of the limestone media onboard.
The ongoing partnership between academic researchers and industrial innovators exemplifies a model for climate tech advancement. Calcarea’s early pilot programs and collaborations with shipping industry leaders, such as Lomar Labs—the corporate venture arm of Lomar Shipping—aim to deploy this technology on working ships in real-world conditions. These trials will elucidate operational controls, integration challenges, and real-time environmental effects, paving the way for regulatory approval and commercialization.
Berelson and Adkins both acknowledge that while the path to widespread adoption will take time, the scale of emissions reduction potential is profound. Capturing half of shipping industry carbon emissions could markedly bend the curve of global greenhouse gas accumulation. The system’s reliance on abundant natural materials, minimal new emissions during operation, and alignment with marine chemistry positions it as an attractive solution in the decarbonization toolkit.
Furthermore, this technology highlights the power of interdisciplinary research—combining marine geochemistry, computational modeling, and engineering—to tackle global sustainability challenges. It opens avenues for further investigation into ocean-based carbon management strategies, potentially expanding beyond shipping to include offshore platforms or coastal installations.
As the shipping industry seeks sustainable solutions that do not compromise operational efficiency or require prohibitively costly vessel redesigns, this accelerated weathering approach provides an innovative, pragmatic alternative. By embracing the ocean’s chemistry itself, humanity gains a powerful ally in the battle against climate change, delivering hope for a cleaner, more sustainable future on the high seas.
Subject of Research:
Article Title: Potential of CO2 sequestration through accelerated weathering of limestone on ships
News Publication Date: 18-Jun-2025
Web References: http://dx.doi.org/10.1126/sciadv.adr7250
References: Science Advances, DOI: 10.1126/sciadv.adr7250
Image Credits: USC
