Rethinking the US-China Farm Trade: Food Exports Could Slash Nitrogen and Climate Pollution

America’s agricultural relationship with China is built on a vast, largely invisible pipeline of animal feed. Every year, enormous quantities of soybeans, maize and other feed crops cross the Pacific, where they are consumed by livestock raised on Chinese farms. A new modeling study published in the journal Nitrogen Cycling on 27 July 2026 suggests that this long-standing arrangement, while beneficial in some respects, leaves a substantial amount of environmental damage on the table. According to the research team led by Xin Zhang of the University of Maryland Center for Environmental Science, replacing feed crop exports with exports of animal-derived food could reduce global nitrogen loss by 38 percent and greenhouse gas emissions by 17 percent compared with the current feed-dominated trade pattern. The finding reframes a debate that has traditionally been argued in terms of commodity volumes and trade balances, adding nutrient pollution, climate impacts and economic returns to the ledger.

The logic behind the result begins with nitrogen, an element that sits at the heart of both agricultural productivity and agricultural pollution. Synthetic fertilizers and manure sustain the world’s crops, but nitrogen that is not taken up by plants leaks into rivers, coastal waters and the atmosphere, contributing to water-quality degradation and greenhouse gas emissions. The study traced nitrogen through the full chain of feed crops, livestock products and manure, estimating emissions from farming, fertilizer use, livestock and international shipping. By following the element across borders, the researchers could compare not just how much is produced, but where it is produced and what happens to the waste streams that production generates. That geographic dimension, the authors argue, is what most previous trade studies, which focused mainly on crops, have missed.

The United States currently enjoys a genuine environmental advantage in growing feed. According to the study, producing feed crops in the United States causes less global nitrogen loss than producing the same feed entirely within China, which is one reason the existing trade pattern is not the worst-case scenario. Under the current arrangement, 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 a hypothetical world in which China produced both the feed and the animal products domestically, the existing trade already reduced global nitrogen loss by 32 percent and emissions by 7 percent. In other words, the trans-Pacific feed trade is already doing some environmental work relative to full domestic production in China.

Yet the current system carries a structural flaw: the feed and the animals that eat it are separated across two countries. That separation limits opportunities to return livestock manure to the fields where the feed is grown, breaking one of agriculture’s oldest nutrient loops. The consequences are quantified in the study, which found that more than 40 percent of the nitrogen in imported feed is lost as manure in China. Manure that cannot be recycled onto cropland becomes a pollutant rather than a resource, driving nitrogen losses that the model captures in its global totals. The researchers suggest that closing this loop, either by moving livestock closer to feed production or by improving manure management, is central to reducing the environmental footprint of the two countries’ intertwined food systems.

To test alternatives, the team constructed three scenarios using 2022 trade data: a baseline with 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 that those feed exports currently support and ships the food itself to China. The modeled switch to food exports produced striking results. Estimated emissions fell to 48 million metric tons of carbon dioxide equivalent, while environmental damage costs dropped by 32 percent relative to current trade. The economic picture improved as well: the shift increased estimated U.S. agricultural trade revenue by 10.5 billion dollars, with a reported uncertainty of 2.4 billion dollars. Exporting finished animal products, in this model, captures more value per unit of environmental impact than exporting the raw feed.

The efficiency story behind these numbers is geographic. The study estimated that feed is converted into animal products more efficiently in the United States than in China, which means that producing a given quantity of pork, poultry or other animal-derived food requires less feed, and therefore less fertilizer and fewer associated nitrogen losses, when the livestock are raised in America. Moving livestock production to the United States would also place animals near the feed fields, making more manure available for use on U.S. cropland and partially restoring the nutrient recycling that the current trade pattern severs. The researchers’ model placed projected production changes across U.S. counties, allowing them to see not only national totals but where the new burdens would actually land.

Those local impacts are the study’s most important caveat. The global gains come with a geographic trade-off: shifting livestock production to the United States increases its estimated emissions and nitrogen pollution, particularly in major livestock-producing areas, even as the corresponding impacts decline in China. Pollution, in other words, does not simply disappear when trade patterns change; it moves. The authors are explicit that their figures are outcomes of modeled scenarios, not predictions that trade will change, and they emphasize that the shift would require additional environmental safeguards in the regions that absorb new production. Their additional scenarios found that combining food waste recovery with improved manure recycling could cut nitrogen loss further and reduce the added U.S. environmental burden, suggesting that policy and technology choices within the importing country shape how large the local cost of the transition would be.

The analytical framework the study offers may prove as consequential as any single number. By accounting for nutrient pollution, climate impacts, environmental damage costs and trade revenue within a single model, the researchers provide a way to assess trade choices that goes beyond commodity flows. The central finding is that the products traded, and where crops and livestock are produced, shape both global environmental totals and local pollution. That insight applies well beyond the U.S.-China corridor, since feed-and-livestock separation is a feature of many international agricultural supply chains. Policymakers weighing trade agreements, tariff structures or sustainability standards could, in principle, use this kind of coupled nitrogen-and-emissions accounting to compare options that look equivalent in purely economic terms but diverge sharply in environmental ones.

The research was supported by the project INFEWS: U.S.-China: Managing agricultural nitrogen to achieve sustainable Food-Energy-Water Nexus in China and the U.S., jointly funded by the U.S. National Science Foundation and the National Natural Science Foundation of China, with additional support to Zhang from the U.S. National Science Foundation. The authors declare no competing interests. As global demand for animal protein continues to rise, the study suggests that the question of what crosses the border, feed or food, is not a trivial detail of logistics but a decision with measurable consequences for nitrogen pollution, greenhouse gas emissions and the communities that bear them. Whether real-world trade evolves toward the modeled scenario remains uncertain, but the analysis makes clear that the environmental stakes of that choice are far larger than the feed trade’s familiar commodity statistics have suggested.

Subject of Research: Environmental impacts of shifting U.S.-China agricultural trade from feed crops to animal-derived food products

Article Title: Trading food instead of feed could cut agricultural pollution

Article References: Trading food instead of feed could cut agricultural pollution. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: agricultural trade, nitrogen pollution, greenhouse gas emissions, U.S.-China trade, livestock production, feed crops, manure recycling, food systems, nitrogen cycling, environmental modeling, sustainable agriculture, trade policy