Oyster farming can sequester carbon dioxide at more than double the rate captured in shells, placing it among the most promising marine-based solutions to climate change, according to a new peer-reviewed study.

The research, published in “Proceedings of the National Academy of Sciences”, shows that oyster-driven carbon storage extends far beyond shell growth.

Organic carbon produced through filter-feeding and later locked in sediments removes 2.39 times more carbon than the calcification process that builds shells.

The study concludes that oyster aquaculture enhances ocean uptake of atmospheric carbon and alleviates acidification.

“Oyster farming provides a dual benefit—supporting global food supply while acting as a nature-based solution to climate change,” said lead author Xue-Wei-Jie Chen of Ocean University of China.

Challenging Old Assumptions

For years, the climate credentials of shellfish aquaculture have been disputed. Some scientists argued that the release of carbon dioxide during shell calcification could offset sequestration, turning farms into net emitters.

The new study challenges that view by presenting what the authors call the first holistic carbon budget for oyster ecosystems. Using 120-day field mesocosm experiments and satellite data from two of China’s largest oyster farms, the team found that carbon dynamics favor storage over release.

“Oyster farms accelerate the ocean’s biological pump, converting atmospheric carbon into organic matter that sinks into seabed sediments,” Chen said.

China’s Role as a Global Leader

China dominates global bivalve production, harvesting 15.1 million tons in 2022. That output, researchers estimate, sequestered about 4.09 million tons of carbon, more than half of which was stored in sediments rather than shells.

Worldwide, aquaculture produced 18.7 million tons of marine mollusks in 2022. With up to 1.5 million square kilometers of ocean suitable for expansion, production could rise to more than 80 million tons by 2050. If scaled responsibly, oyster farming could make a measurable contribution to international climate goals, the study suggests.

By comparison, many engineered carbon removal technologies remain costly or unproven at scale. Oyster farming, however, already supports coastal economies and food security, especially in Asia.

Stocking Density Matters

The study found that the benefits of oyster farming depend on stocking practices. Moderate densities encouraged phytoplankton growth, enhancing the biological pump and boosting sequestration efficiency.

High densities, by contrast, triggered a “clarity effect,” where excessive filter-feeding depleted phytoplankton biomass, reducing carbon capture efficiency.

In mesocosm trials, high-density systems yielded less dissolved and particulate organic carbon, even though shell growth continued.

“This shows there is an ecological balance point,” Chen said. “Too many oysters in one area can reduce the efficiency of carbon storage.”

The researchers argue that managing stocking densities could maximize carbon benefits while sustaining yields for food production.

Implications for Blue Carbon Markets

The findings could reshape how regulators and investors view shellfish farming. At present, bivalve aquaculture is excluded from most carbon trading schemes and blue carbon frameworks due to uncertainty over its net impact.

By quantifying both organic carbon sequestration and shell-based storage, the new research provides evidence for its inclusion in climate finance mechanisms.

The authors suggest using a broader carbon influx metric, one that incorporates sediment storage and organic matter deposition, rather than relying only on shell weight as a measure.

Globally, carbon trading markets are projected to exceed $100 billion by 2030. Recognizing oyster farming’s role could open new revenue streams for coastal farmers while incentivizing sustainable practices.

Balancing Food and Climate Priorities

The potential of oyster farming lies in its dual role. It provides protein with relatively low environmental impact compared to livestock and land-based aquaculture.

It also helps conserve arable land and freshwater resources, aligning with United Nations goals on food security.

By enhancing water pH and countering acidification, oyster farms may also create more stable environments for marine biodiversity. Still, researchers caution that the sequestration potential is subject to local ecological conditions, including water turbidity and nutrient flows.

“Not all farms will deliver the same carbon benefits,” Chen said. “But our results show oyster aquaculture, when managed wisely, can play a significant role in both climate mitigation and food production.”

Looking Ahead

The study adds momentum to calls for integrating nature-based solutions into climate strategies. Alongside seaweed farming and mangrove restoration, shellfish aquaculture is increasingly seen as part of the ocean-climate toolbox.

If scaled globally, oyster farming could rival some engineered carbon dioxide capture projects in impact, while offering added social and economic benefits. For policymakers and ESG investors, the message is clear: oyster farms are more than a seafood supply; they are living carbon pumps.

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