The term aquaculture describes the breeding, raising and harvesting of organisms such as fish, crustaceans and algae in all types of water. It is becoming an increasingly important source of protein for people in many countries and regions.
However, with this expansion of aquaculture comes a corresponding increase in greenhouse gas (GHG) emissions, which are major contributors to global warming and climate change.
As China is a world leader in aquaculture culture, a research group led by the Institute of Hydrobiology of the Chinese Academy of Sciences conducted a study to find out the levels of GHG emissions produced by the country’s aquaculture. . Their results, published in the journal KeAi Water biology and safetyshow that the production of food used to feed fish is one of the largest contributors to industry GHG emissions.
According to Professor Jun Xu, group leader of the study, the team started by measuring GHG emissions from four key aquaculture processes. They took into account energy consumption, for example the energy used to pump water, provide lighting and power vehicles on fish farms. They also looked at nitrous oxide generated by animal feces and excess food in the water, and they investigated the production of synthetic fertilizers applied to increase productivity. The fourth element they considered was the manufacture of animal feed, raw materials such as soybean meal, wheat and fishmeal, and the emissions resulting from their production, processing and their transportation. They then measured the carbon footprint of each of these processes over the past 10 years, dividing the results by region and by nine major groups of fish species.
Professor Xu notes: “The results show that the production of raw materials contributed the most to GHG emissions. Spatial analysis showed that Guangdong, Hubei, Jiangsu and Shandong had the highest GHG emissions of all 31 provinces surveyed, accounting for around 46% of all emissions.
The team also found a significant positive correlation between regional gross domestic product (GDP) and GHG emissions in each province (>0.6). Professor Xu explains: “The aquaculture and mariculture industries have developed rapidly in China, and increased production is often accompanied by higher regional GDP. Rapid economic and social development is leading to higher levels of consumer demand for aquaculture and mariculture products. This in turn leads to the expansion of these industries in provinces with higher regional GDP.
The team’s results also show that Chinese aquaculture had a lower emission intensity (2.7) than the global value (3.3) published by the Food and Agriculture Organization of the United Nations. . They believe this is due to the higher percentage of bivalve production in China. The bivalve – an aquatic mollusk – generally gets its nutrients directly from water, eliminating the need for manufactured foods.
Professor Xu says, “Studies on the quantification of GHG emissions from aquaculture are rare in China. Our study reveals, for the first time, the relationship between relative yield per species composition and spatial distribution. Importantly, it provides the scientific basis for reducing GHG emissions in the broader context of expanding aquaculture in the future. But it is clear that more work is needed to better understand the mechanism of the process.
He adds: “We suggest that managers and local governments adjust the relative proportion of production of species groups and change the source of energy use to reduce the carbon footprint of the industry. We believe this work has implications for the future of the Chinese aquaculture industry and aquaculture in countries facing similar issues, such as Indonesia and Bangladesh.