Animal feed and greenhouse gas emissions in the United States and China

By Karen Mancl

“Save your kitchen scraps to feed the hens,” urged a poster for the victory gardens created on the home front in the Second World War. Feeding food scraps to backyard chickens and pigs turned this waste into a delicious source of human food. Pigs were especially prized in this effort as they would eat what most other animals considered inedible.

Times have changed in both the United States and China. Chinese farms are the world’s number one chicken producers and raise half the world’s pigs. Today, most U.S. farms feed grain to pigs and chickens. China recently halted its widespread use of food waste to supply chicken and pigs after an outbreak of disease in 2019. 

Perhaps going back to past methods might create a greener future. Today, a third of food grown globally is wasted, and as it decomposes it emits methane that is 80 times more potent than carbon dioxide.

The United States and China are the biggest contributors of these methane emissions. Moving animal feed onto the climate agenda is one way both countries could work together. The U.S. and China might find better ways to reuse food waste as animal feed creating a win-win climate solution.

Disease changed food waste as animal feed

Until 2019, the collection and transport of food waste from restaurants, hotels, and cafeterias in China was a booming industry to supply China’s chicken and pig farms. However, food waste practices changed in China, after an outbreak of African Swine Fever that in one year killed more than 120 million pigs—a quarter of China’s total population. In response, China banned feeding food waste to pigs, because the virus was found in food waste coming from the meat of infected pigs.

Public health also resulted in change in the U.S. a decade earlier. In 2009, the U.S.  Congress passed the Swine Health Protection Act. While the U.S. government does still permit food waste as feed, farmers must be licensed to collect it from restaurants, school cafeterias and food processing plants. They also must cook any pathogens from food waste after its collection. Even with these protections in place, 23 states still prohibit the practice entirely.

Grain also contributes to greenhouse gas emissions

Instead of using food waste, Chinese farmers have switched to buying corn and soybean meal to feed pigs and chickens. Of all the energy it takes to produce corn grain, 33% is used to dry it for storage. In an interview, Dirk Maier, Agricultural Engineering Professor at Iowa State University, observed that for every metric ton of corn handled, dried, and stored, 58.3 kg of carbon dioxide equivalent (CO2e) is released into the atmosphere. The fact that the United States alone stores about 6 billion tons of grain makes the CO2 emitted from grain drying a significant and unaddressed agricultural source of greenhouse gas emission.

The situation in China is similar. Liu Xiangdong, a Professor in the College of Engineering at the China Agricultural University, found that 83% of grain is dried using coal, so this practice is a large emitter of greenhouse gas as well. Grain drying in China emits just under 6 million tons of carbon dioxide annually, making it the most energy intensive and polluting process in the grain industry.

Animal feed and climate policy

In 2011, the U.S. Environmental Protection Agency launched its Food Recovery Challenge to capture food scraps. In the first year, 77 grocery stores, universities, and sports and entertainment venues took up the challenge. One of the biggest success stories was the MGM resorts in Las Vegas, which started collecting food waste from its restaurants and dining rooms in 2012. In 2017, 1,904 tons of food waste from the Bellagio Hotel were fed to 3,000 pigs on a farm north of the city.

Claudia Fabiano, an Environmental Protection Specialist in the EPA’s Office of Resource Conservation and Recovery, described how feeding food waste to animals is considered highly circular usage — since it maintains the original intent for food, which is to nourish people.

Canada is taking on leadership in reducing the climate footprint of grain drying. Its government is offering sticks — a new carbon tax on fuel for grain drying increases grain production costs $20 USD per hectare — as well as carrots. These incentives have taken the form of a $50 million Agricultural Clean Technology Program that Canada launched in 2021 as a part of its 2030 Emissions Reduction Plan. This program supports farmers as they upgrade old propane dryers to a new carbon-neutral system.

In the United States, farmers are encouraged to replace old, polluting grain dryers with new, efficient equipment through the Farm Bill Environmental Quality Incentive Program (EQIP). Financial assistance is made available after farmers conduct an energy audit and develop an Agricultural Energy Management Plan. Additional cost-share funds also are now available through the Inflation Reduction Act Rural Energy Assistance Program. Farms and rural businesses can use the funds to shift grain drying to renewable energy systems.

China’s animal feed sector is still reacting to world trade policies and disease outbreaks, and food waste is not yet being considered as a way to reduce greenhouse gas emissions. Following the devastating impact of African Swine Fever, livestock operations are being modernized and intensified to increase efficiency and biosecurity. Chinese researchers are just starting to explore the impact of these shifts and government policies on food waste from rural households where scraps that once fed animals are now going to landfills and increasing reliance on imported grain and synthetic feed additives.

Greenhouse gas emissions from the animal feed sector are unexpectedly impacted by a wide range of international policies. Collaboration on finding safe ways to feed livestock food waste and developing alternative energy grain drying systems would help both China and the United States find win-win solutions to produce greener eggs and ham.

Karen Mancl is a Professor in the Ohio State University Department of Food, Agricultural & Biological Engineering. This column is provided by the OSU Department of Food, Agricultural & Biological Engineering, OSU Extension, Ohio Agricultural Research and Development Center, and the College of Food, Agricultural and Environmental Sciences. For more information, Mancl can be reached at 614-292-4505 or You can also check her website at

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