Life cycle assessment of diploid and triploid oyster farming: A case study in Zhanjiang, China.

Growing pressure to mitigate the environmental impacts of food production systems has made the development of sustainable protein sources a priority at the global level. Oyster farming constitutes a pivotal component of the blue food system, yet, in China, the environmental impacts of this sector remain poorly characterized, primarily because of highly diversified farming practices and pronounced regional heterogeneity across the tropical coastal waters of the south. To fill the information gap, this study performed a "cradle to gate" life cycle assessment for two commercially dominant taxa farmed in the Zhanjiang region: the native Crassostrea hongkongensis and the introduced triploid Crassostrea angulata. Through field research on seven farming models, the study found that the carbon footprint of triploid C. angulata (89.04∼105.18 kg CO2-eq t-1) was lower than that of C. hongkongensis (133.85∼178.85 kg CO2-eq t-1). In terms of environmental impacts, polyurethane foam floats in C. hongkongensis farming were the primary source of greenhouse gas (GHG) emissions (contributing 51.61%), freshwater eutrophication, marine eutrophication and water consumption, whereas the environmental impacts of triploid C. angulata were mainly driven by the seedling stage, diesel consumption, and float ball. Furthermore, on 1 kg protein basis, the GHG emissions of both oyster types (2.67∼9.00 kg CO2-eq kg-1) were significantly lower than those of traditional animal products such as beef and pork. Scenario analysis demonstrates that through the adoption of recycled plastic float barrels, extension of facility service life, and optimization of attachment substrates, the following maximum reduction potentials can be achieved across different environmental impact categories: 31.57% for global warming, 26.27% for terrestrial acidification, 58.72% for freshwater eutrophication, 95.05% for marine eutrophication, 6.07% for land use, and 65.99% for water consumption. These findings corroborate that C. hongkongensis and triploid C. angulata farming in the Zhanjiang coastal system constitutes a premium low environmental impacts protein source and can make a material contribution to low-carbon blue food production.