Consider the idea of sustainable cuisine. While humble lentils may come to mind, is it feasible to indulge in luxurious options while remaining eco-conscious? Bivalves like oysters, mussels, scallops, and clams possess inherent green credentials thanks to their ability to purify polluted waters. Recent research indicates they might also help sequester carbon. Could agricultural bivalves emerge as the pinnacle of sustainable food?

Food production contributes to around a third of global greenhouse gas emissions, making it crucial to identify options that mitigate this damage. In seafood, aquaculture is generally more sustainable than wild fishing; however, farmed fish rely on wild fish for part of their diet. Recent studies reveal that the reliance on wild fish for aquaculture feed is often underestimated. Additionally, fish farms can create significant waste issues from fish excrement and uneaten feed.

A notable advantage of bivalves is their minimal need for supplemental feed. As filter feeders, they consume tiny nutrient particles suspended in seawater and plankton. With most coastal waters currently suffering from nutrient overload due to nitrogen and phosphorus runoff, harvesting cultivated bivalves can help alleviate this excess and purify the waters as a byproduct of their production.

Conversely, harvesting wild bivalves poses ecological threats. For instance, overfishing of wild scallops can damage delicate marine ecosystems like seafans, corals, and sponges. However, comparison shows that farmed bivalves come with significantly fewer drawbacks, especially when compared to rainforest destruction for beef production.

But there’s more to explore. In recent years, various studies have suggested that agricultural bivalves can sequester carbon, potentially allowing farms to earn carbon credits as an additional revenue stream.

Yet, Fabrice Pernett from Brest University in France remains skeptical. A review of over 50 studies has left him unconvinced. Many of these studies are based on theoretical models that assume the formation of calcium carbonate shells absorbs CO.₂ from the sea.

However, this phenomenon holds true only over geological timescales. Over shorter periods—critical when addressing climate change—the carbon cycle shows carbonate formation often releases CO.₂.

Moreover, the common practice of incinerating waste shells frequently leads to even more CO.₂ being released into the atmosphere instead of returning carbon to the ocean to mitigate CO.₂ emissions. Similarly, carbon from the flesh of seafood also gets released as CO.₂ following consumption.

Some researchers are now claiming that organic matter deposited under bivalves represents a significant carbon sink.

This latest assertion builds upon oyster research conducted within five large enclosures. However, Pernett cautions that similar studies feature shortcomings, such as CO.₂ measurements being conducted only during the day and summer months when photosynthesis peaks.

The research team argues this limitation does not influence the findings. “The budget suggests that carbon accumulation and sequestration exceed carbon extracted in shells,” asserts Shuang-lin Dong from China Maritime University. Nevertheless, Pernett is still unconvinced. “Current evidence indicates that bivalve farming releases CO.₂ overall,” he remarks.

However, don’t cancel your reservation at your favorite oyster bar just yet. Although bivalve farming may be a carbon emitter, the emissions are relatively low—around 1.4 kilograms of CO.₂ per kilogram of edible weight based on 2021 research. This figures significantly lower than that of wheat or corn, all while requiring less land and freshwater.

“Indeed, agricultural bivalves rank among the greenest food sources,” states Pernett. A culinary delight.

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