| Since the 1980s, China's aquaculture industry has experienced rapid development and sustained growth in aquaculture production, which has not only provided large quantities of high-quality protein for humans, but has also become an important supplement to ensure world food security. The salinity adaptation range of Litopenaeus vannamei is extensive, so it can be cultured in both saline water and freshwater. China has 690 million acres of saline water resources, offering significant potential for the aquaculture of L. vannamei. While providing protein for a fast-growing human population, the ongoing boom in aquaculture incurs environmental costs. Carbon emissions are generated during the aquaculture process, and assessing the carbon footprint of seafood aquaculture is essential for establishing targeted emissions reduction and carbon sink enhancement strategies, which are vital for achieving the "Carbon Peak and Carbon Neutrality" goals. Carbon footprint is defined as the total amount of greenhouse gases emitted, either directly or indirectly, by an individual, organization, event, or product throughout its life cycle, typically expressed in terms of CO2 equivalent (CO2e). This metric provides a comprehensive and intuitive understanding of the environmental impacts of human activities and facilitates the development of targeted emission reduction and carbon sink enhancement strategies. The most commonly employed method for carbon footprint accounting is Life Cycle Assessment (LCA), which consists of four key parts: (1) target and scope definition, (2) inventory analysis, (3) impact assessment, and (4) interpretation of results. In this study, the carbon footprint of L. vannamei pond culture was assessed using "gate-to-gate" LCA methodology, based on primary data from on-site monitoring of culture ponds and aquaculture enterprises in Shandong Province. It was found that the carbon footprint for producing 1 kg of L. vannamei was 5.60 kgCO2e, with total carbon emissions amounting to 7.69 kgCO2e. These emissions during aquaculture primarily stem from the use of chicken manure, lime, and feed, while the net carbon uptake by the pond ecosystem, attributed to the abundance of various algal species, is 2.09 kgCO2e. Notably, carbon emissions from the aquaculture process alone reached 7.42 kgCO2e, constituting 96.5% of total emissions, while emissions from pond construction and decommissioning was only 0.27 kgCO2e, accounting for 3.5% of the total emissions. Among the sources of carbon emissions, chicken manure used for fertilization represented the largest share, contributing 5.62 kgCO2e and accounting for 73% of total emissions during the shrimp culture phase. This was followed by compounded feeds, which contributed 0.87 CO2e/kg, representing 11.3% of total emissions, while quicklime accounted for 10.7% of the total emissions at 0.82 kgCO2e. Additionally, diesel fuel and materials such as electricity and polyethylene contributed approximately 5% of the total carbon emissions. The predominant farming methods of L. vannamei in China include factory farming, semi-intensive ponds, small shed culture and pond aquaculture. Analysis of existing research indicates that the carbon footprints of 1 kg of L. vannamei farmed year-on-year of different farming methods are in the following order from smallest to largest: large surface culture (5.60 kgCO2e) < small shed culture (18.25 kgCO2e) < semi-intensive ponds (52.3 kgCO2e) < factory farming (198 kgCO2e). It is necessary to explore a win-win aquaculture model for economic and ecological benefits from the multidimensional perspective of green, sustainable, and efficient aquaculture. By comparison of the other referred carbon footprint results of farmed seafood based on the LCA method, including Megalobrama amblycephala (29 kgCO2e/kg), Scophthalmus maximus (19.4 kgCO2e/kg), Stichopus japonicus (0.27~38.89 kgCO2e/kg), Lamellibranchia (1.41 kgCO2e/kg), Larimichthys crocea (10.55~75.5 kgCO2e/kg) and Laminaria japonica (-0.10 kgCO2e/kg). The carbon footprint of aquaculture of L. vannamei in large surface ponds in Binzhou is 5.60 kgCO2e/kg, which is much lower than that of M. amblycephala, S. japonicus, L. crocea and other aquatic products. Under equivalent intake conditions, substituting high carbon emissions seafood products with L. vannamei of low carbon emissions can effectively reduce overall carbon emissions. To mitigate emissions from L. vannamei aquaculture in large water surface ponds, several recommendations are proposed. Firstly, the excessive use of chicken manure as fertilizer, as indicated by pond monitoring results, should be moderated to optimize application rates. Currently, farming enterprises often apply chicken manure without adequate scientific guidance, necessitating further research to refine fertilization practices. Secondly, problems such as less refined culture techniques and lower bait utilization exist during large water surface culture. Therefore, it is necessary to improve shrimp survival and reduce carbon emissions by refined pond culture management as well as optimizing feeding strategies and bait structure. Moreover, the recapture rate of shrimp in large surface culture is currently less than 30%, which could be improved by adding filter-feeding shellfish into shrimp pond. This approach would not only reduce carbon emissions associated with organic pollutants but also enhance the efficiency of material cycling in the aquatic ecosystem and improve water quality, ultimately benefiting shrimp survival rates. Last but not least, establishing and refining the L. vannamei carbon footprint labeling can guide the market of green consumption and promote the sustainable development of green industry. Consequently, scientific fertilization, precision feeding, and algae-shellfish integrated aquaculture are critical to achieving emissions reductions and enhancing carbon sinks in large surface culture systems of L. vannamei. This study can provide support for carbon accounting of L. vannamei pond aquaculture. |
