Researchers have successfully demonstrated a novel method for removing dissolved carbon dioxide from the ocean and converting it into a precursor for biodegradable plastics. The innovative system integrates an electrochemical process with engineered marine microbes, offering a potential pathway to mitigate ocean acidification while simultaneously creating a sustainable alternative to petroleum-based polymers.
This new technology addresses two significant environmental challenges by treating oceanic carbon not as a waste product to be sequestered, but as a valuable resource for a circular economy. By pulling CO2 directly from seawater and using it as a feedstock, the process creates the chemical building blocks for eco-friendly materials that can decompose naturally, unlike conventional plastics. The entire system is designed for high efficiency and durability, representing a key step toward scalable and economically viable ocean carbon capture.
A Durable Seawater Capture System
The world’s oceans are the planet’s largest carbon sink, storing significantly more carbon than the atmosphere. Tapping into this vast reservoir is a promising strategy, but previous attempts at direct ocean capture have been hampered by technical challenges. Electrochemical systems often failed quickly, sometimes within hours, because minerals like magnesium and calcium in seawater would precipitate onto core components, causing scaling and clogging.
To overcome this, scientists from the Chinese Academy of Sciences and the University of Electronic Science and Technology of China developed a redesigned electrolysis system. This new device uses a solid-state electrolyte and membranes to isolate sensitive components from direct contact with seawater. The system first acidifies the seawater, which forces the dissolved bicarbonate and carbonate ions to revert into pure carbon dioxide gas that can be reliably collected. The process proved remarkably stable, operating continuously for 536 hours—more than 22 days—in a test using water from Shenzhen Bay. Afterward, the system restores the water’s original chemistry before returning it to the ocean.
From Captured Gas to Microbial Feedstock
Capturing CO2 gas is only the first part of the integrated process. The ultimate goal was to convert the captured carbon into a high-value, useful chemical. To achieve this, the team designed a second stage to transform the collected CO2 into a molecule that microorganisms could readily consume.
In this second reactor, the gas is converted into formic acid using a specialized bismuth-based catalyst. Formic acid, a simple one-carbon molecule also found in nature as an insect defense mechanism, is an energy-rich and biologically friendly compound. This pure, concentrated liquid serves as the perfect intermediate, acting as an exclusive food source for the engineered microbes in the next and final stage of the production chain.
The Biological Conversion Engine
Engineered Marine Microbes
The final and most innovative step involves harnessing the power of biology. The researchers turned to a fast-growing marine bacterium called Vibrio natriegens, which they genetically engineered for the specific task. These microbes were cultured and fed the formic acid produced in the preceding step as their sole source of carbon. The use of a native marine bacterium is a notable element of the design, ensuring the biological component is well-suited to a saline environment and can thrive on the provided feedstock.
Producing the Plastic Precursor
As the engineered bacteria metabolize the formic acid, their biological processes efficiently convert it into succinic acid. Succinic acid is a widely used and valuable platform chemical that serves as a key precursor for manufacturing biodegradable plastics, specifically polybutylene succinate (PBS). This bio-based succinic acid can then be used directly as a building block for creating polymers that are both sustainable and capable of decomposing, unlike traditional plastics that persist for centuries in the environment. The process effectively turns carbon from the ocean into the foundation of an eco-friendly material.
Evaluating Efficiency and Scalability
The new integrated system demonstrates significant gains in performance over previous carbon capture technologies. The entire process operates at an impressive overall efficiency of approximately 70%. Furthermore, it is relatively energy-thrifty, consuming just 3 kilowatt-hours of electricity per kilogram of CO2 extracted. This efficiency leads to a projected cost of around $230 per ton of CO2 captured and converted, a figure that compares favorably to many existing methods.
While these initial results are highly promising, the research has been demonstrated at a laboratory scale. Successfully applying the technology at an industrial scale to make a meaningful impact on ocean CO2 levels remains a significant future challenge. However, the published work, appearing in Nature Catalysis, provides a strong proof-of-concept for a complete system that is more durable and cost-effective than its predecessors.
Implications for a Circular Economy
The research represents a critical advancement in how we approach climate technology. Instead of simply capturing and storing carbon, this method repurposes it into something useful and economically valuable. This model helps create a circular carbon economy where greenhouse gases are treated as a raw material for greener manufacturing rather than just a pollutant to be buried.
By simultaneously reducing CO2 levels in the ocean—which helps to combat ocean acidification—and producing a sustainable material, this technology offers a multi-faceted solution. It shows a promising path forward for developing systems that can help restore environmental balance while also contributing to a more sustainable industrial future. This linkage of carbon capture with green chemistry could pave the way for a new generation of climate solutions.