Turning ocean CO₂ into biodegradable plastic

October 22, 2025

A groundbreaking innovation by researchers in China has unveiled a revolutionary method to capture carbon dioxide (CO₂) directly from ocean water and transform it into succinic acid — a vital ingredient in producing biodegradable plastics such as polybutylene succinate (PBS). The study, recently published in Nature Catalysis (Nat. Catal. 2025, DOI: 10.1038/s41929-025-01416-4), highlights a scalable pathway toward eco-friendly materials, sustainable fuels, and green chemical production.

Harnessing ocean carbon for clean manufacturing

The new system, developed by Chuan Xia and Xiang Gao from the University of Electronic Science and Technology of China and the Shenzhen Institute of Advanced Technology, offers a practical alternative to energy-intensive air capture technologies.

“This process leverages the ocean’s dissolved carbon to produce low-carbon chemicals,” explains Xia. “It eliminates the high energy costs of direct air capture while supporting coastal, renewable-powered manufacturing.”

While global efforts focus on large-scale carbon capture from the atmosphere, the ocean already absorbs about one-third of human-generated CO₂. Extracting carbon from seawater — known as Direct Ocean Capture (DOC) — is emerging as a more efficient, sustainable solution.

First to convert captured ocean CO₂ into bioplastics

Until now, no system had successfully integrated DOC with chemical conversion. “This is the first demonstration of transforming ocean-captured CO₂ directly into a bioplastic feedstock,” says CX Xiang, materials scientist at Caltech and CTO of DOC start-up Captura, who was not involved in the project.

The process uses electrochemistry and microbial fermentation in a five-chamber reactor. Each compartment is separated by specialized membranes to prevent scaling and fouling — common issues in seawater-based systems.

How the ocean carbon capture system works

1. Electrolysis and Ion Separation:
The reactor splits water into hydroxide and hydrogen ions using an electric field. Sodium and chloride ions are also separated, forming sodium hydroxide in the process.

2. CO₂ Extraction from Seawater:
Acidified seawater in one chamber converts dissolved carbonate ions into CO₂ gas.

3. Catalytic Conversion:
The CO₂ passes through a bismuth-based metal-organic framework catalyst, converting it into formic acid.

4. Microbial Fermentation:
Engineered Vibrio natriegens bacteria ferment the formic acid, producing succinic acid — a core monomer for biodegradable plastics.
Researchers note the system could be adapted to make other chemicals like lactic acid, alanine, or butanediol, supporting broader bio-manufacturing.

5. Ocean-Safe Discharge:
The remaining seawater is neutralized with the produced sodium hydroxide, ensuring safe return to the ocean ecosystem.

Efficiency, longevity, and cost competitiveness

Unlike previous DOC systems that degrade within hours, Xia’s design ran continuously for over 530 hours using real seawater from Shenzhen Bay. It extracted 6.54 liters of CO₂ from 177 liters of seawater, achieving a 70% carbon capture efficiency.

The reactor consumed only 3 kWh of energy per kilogram of CO₂, with a projected capture cost of $230 per metric ton — comparable to existing carbon capture technologies.

Although Captura’s approach boasts higher efficiency (around 90%) and lower energy use, Xiang acknowledges that this new system’s true innovation lies in CO₂ utilization. “The key breakthrough isn’t just capturing carbon,” he says, “but converting it directly into valuable bioplastics that could transform sustainable manufacturing.”