Low Greenhouse Gas Emissions from Oyster Aquaculture

Production of animal protein is associated with high greenhouse gas (GHG) emissions. Globally, oyster aquaculture is increasing as a way to meet growing demands for protein, yet its associated GHG-emissions are largely unknown. We quantified oyster aquaculture GHG-emissions from the three main constituents of GHG-release associated with terrestrial livestock production: fermentation in the animal gut, manure management, and fodder production. We found that oysters release no methane (CH₄) and only negligible amounts of nitrous oxide (0.00012 ± 0.00004 μmol N₂O gDW^-1 hr^-1) and carbon dioxide (3.556 ± 0.471 μmol CO₂ gDW^-1 hr^-1). Further, sediment fluxes of N₂O and CH₄ were unchanged in the presence of oyster aquaculture, regardless of the length of time it had been in place. Sediment CO₂ release was slightly stimulated between 4 and 6 years of aquaculture presence and then returned to baseline levels but was not significantly different between aquaculture and a control site when all ages of culture were pooled. There is no GHG-release from oyster fodder production. Considering the main drivers of GHG-release in terrestrial livestock systems, oyster aquaculture has less than 0.5% of the GHG-cost of beef, small ruminants, pork, and poultry in terms of CO₂-equivalents per kg protein, suggesting that shellfish aquaculture may provide a a low GHG alternative for future animal protein production compared to land based sources. We estimate that if 10% of the protein from beef consumption in the United States was replaced with protein from oysters, the GHG savings would be equivalent to 10.8 million fewer cars on the road.