New research from Ireland adds to the mounting evidence that bivalve aquaculture can provide benefits for climate and nutrition. The recent study finds that Irish oyster farms remove 228% more nutrients than they produce, provide coastal cleanup to the value of $2 million, and lock away tons of carbon in their shells.
While research on bivalves is increasing, this study is one of the few that look at the ecosystem services that bivalve farming provides, and then contextualizes this within the industry’s environmental impacts, to provide more accurate estimates. It also provides rare insights from the industry in Europe: most bivalve studies are based in the United States, where conditions and therefore outcomes may be different.
Writing in npg Sustainable Agriculture, the team of scientists explain that they collected samples of Pacific oysters from two farms in the northwest of Ireland, which were then dried and ground up finely so that the team could analyze the carbon and nitrogen captured in their tissues and shells. The researchers also gathered operational data from three farms in the region that helped them carry out a lifecycle analysis on oysters, from production to farmgate, which included everything from the the fuels used in oyster-harvesting equipment, to the polyethene material used to bag them up.
They then extrapolated these results to the nationwide scale, to assess the industry’s impact and potential benefit in Ireland overall.
In terms of impact, the lifecycle analysis found that a tonne of oysters produces about 370 kilograms of CO2 equivalent, and 0.39 kilos of phosphorus equivalent (which represents nutrient pollution). The main contributors to the CO2 emissions were the use of electricity to drive the on-site oyster-grading equipment, and the production and combustion of diesel fuels for harvesting machinery.
On the other hand, the ecosystem services provided by oyster farms either completely or significantly offset these effects. Carbon-wise, the oyster farms in the experiment bound the equivalent of almost 275 kilos of CO2 in their shells, which offset the carbon impacts of their lifecycle by 73%.
Furthermore, the dried oyster analysis found that the bivalves soaked up the equivalent of 2.36 kilograms of phosphorus per tonne (which included nitrogen and phosphorus in one figure). That is roughly six-fold—or 228% more—than the nutrient pollution they generate, the researchers say.
When they expanded these results to the national context, the study found that oyster farms could collectively remove 40 tonnes of nitrogen, and 4 tonnes of phosphorus, per year. That would clear coastal nutrient pollution equivalent to €1.9 million ($2.13 million) annually. This would be the nitrogen content equivalent of the wastewater generated by over 10,000 people each year.
Meanwhile, in carbon terms oysters farms are capable of removing almost 835 tonnes of carbon per year at the national scale, which could be temporarily or permanently sequestered depending on how oyster shells are handled after harvesting.
Per kilogram of protein generated, Irish oysters would produce 5.71 kilos of CO2 equivalent (this number incorporates their carbon-sequestering benefits), which is roughly a tenth of what beef generates per kilo of protein. The study notes that the carbon sequestering potential of oysters is also higher when compared to other bivalves like mussels and clams.
All this adds to mounting evidence on the dual nutritional and climate benefits of oyster farming worldwide. Meanwhile, the study shows the advantages of investing in oyster farming specifically in the European context, where it’s currently experiencing a decline, but could help the region meet its climate goals, the researchers say.
Costa Domech et. al. “Oysters, a sustainable bluefood?” npg Sustainable Agriculture. 2025.
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