The United States currently exports large quantities of soybeans, maize and other feed crops to China, where they support livestock production. This arrangement has advantages: growing the feed in the United States causes less global nitrogen loss than producing the same feed entirely in China, according to the study. Yet the feed and the animals that consume it are largely separated across two countries.
That separation limits opportunities to return livestock manure to the fields where feed is grown, and more than 40% of the nitrogen in imported feed is lost as manure in China. Previous trade studies have focused mainly on crops, leaving the consequences of trading feed versus animal-derived food less clearly understood.
A study (DOI: 10.48130/nc-0026-0011) published in Nitrogen Cycling on 27 July 2026 by Xin Zhang's team, University of Maryland Center for Environmental Science, found that exporting animal-derived food instead of feed could lower global nitrogen loss, greenhouse gas emissions and estimated environmental damage costs.
Using 2022 trade data, the team compared three scenarios: no bilateral feed or food trade, the existing pattern of predominantly feed exports, and a hypothetical shift in which the United States produces the animal products supported by those feed exports and ships the food to China. The calculations traced nitrogen through feed crops, livestock products and manure, then estimated emissions from farming, fertilizer, livestock and international shipping. The researchers also assessed trade revenue, placed projected production changes across U.S. counties, and tested whether recycling plant-based food waste and manure could reduce impacts.
Under the existing trade pattern, production linked to the traded commodities generated an estimated 1.3 million metric tons of nitrogen loss and 57 million metric tons of carbon dioxide equivalent in greenhouse gas emissions. Compared with producing the feed and animal products entirely in China, current trade already reduced global nitrogen loss by 32% and emissions by 7%. The modeled switch to food exports reduced those impacts further: estimated emissions fell to 48 million metric tons of carbon dioxide equivalent, while environmental damage costs fell by 32% relative to current trade.
It also increased estimated U.S. agricultural trade revenue by $10.5 billion, with a reported uncertainty of $2.4 billion. Those global gains came with a geographic trade-off. Moving livestock production to the United States increased its estimated emissions and nitrogen pollution, particularly in major livestock-producing areas, even as impacts declined in China. Producing animals closer to U.S. feed fields would also make more manure available for use on cropland. In additional scenarios, the team found that combining food waste recovery with improved manure recycling could cut nitrogen loss further and reduce the added U.S. environmental burden.
The study presents these figures as outcomes of modeled scenarios, not predictions that trade will change. Its central finding is that the products traded - and where crops and livestock are produced - shape both global environmental totals and local pollution. Accounting for those effects, alongside practical improvements in nutrient recycling, could help policymakers evaluate agricultural trade options more fully.