Oceans absorb roughly one-third of global CO2 emissions, but extracting and reusing that dissolved carbon efficiently has remained an unresolved challenge. Until now, no system has successfully combined direct ocean capture (DOC) with immediate CO2-to-chemical conversion.
The new system integrates electrochemistry and microbial fermentation in a sequential process. Seawater is pumped into a five-chamber electrochemical reactor, where an applied electric field drives water splitting and generates protons. These protons acidify one of the chambers, shifting pH to transform dissolved carbonates into gaseous CO2.
The released CO2 passes through a hollow-fiber membrane to a second reactor, where a bismuth-based catalyst converts it selectively into formic acid. This formic acid then serves as feedstock for an engineered strain of Vibrio natriegens, which ferments it into succinic acid - a vital precursor for the biodegradable polymer polybutylene succinate.
In extended trials using seawater drawn from Shenzhen Bay, the reactor continuously extracted CO2 for over 530 hours, maintaining a 70 percent carbon capture efficiency. The estimated cost of capture was around $230 per metric ton of CO2 - comparable with leading carbon capture systems.
By substituting different engineered microbes, the platform could also yield other industrially valuable chemicals, including lactic acid, alanine, and 1,4-butanediol.
"This is the first demonstration that's going from ocean CO2 all the way to a usable feedstock for bioplastic. The true focal point is taking that CO2 and turning it into a bioplastic monomer with promising stability and economics," said XIANG Chengxiang, a chemical physics and materials science expert at the California Institute of Technology, who was not involved in the study.
The researchers highlight that this artificial ocean carbon recycling system presents a scalable route for transforming oceanic carbon into sustainable materials, paving the way for new electrochemical-biological manufacturing processes.
Research Report:Efficient and scalable upcycling of oceanic carbon sources into bioplastic monomers
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