Abstract
Current U.S.-China agricultural trade primarily consists of crops used for animal feed, which are pivotal in China's livestock production. Trade policies between these nations have been predominantly driven by economic interests and political relations, but here we show that they also have large consequences for nitrogen pollution, which also merits consideration. More than 40% of nitrogen in feed is lost into the environment as manure, exacerbating nitrogen pollution in China while increasing energy and water consumption for producing synthetic fertilizer in the U.S. Instead of trading feed, trading animal-derived food would lower overall nitrogen pollution and alter its distribution. Transitioning from trading feed to food could reduce total nitrogen loss and greenhouse gas emissions by over 30%, significantly cutting manure pollution in China and reducing synthetic fertilizer use through substitution by manure in the U.S. Transitioning to greater food trade would increase nitrogen losses and associated environmental damage costs in the U.S. However, increased losses could be mitigated by over 40%, resulting in comparable environmental impacts to the current feed trade situation, by recovering and diverting plant-based human food waste for animal feed and increasing manure recycling. The U.S. agricultural trade revenue would increase by US$11 ± 3 billion. Optimizing agricultural trade portfolio between China and the U.S. considering the impacts on both the environment and the economy could benefit both countries.