Just the facts. From the experts.


We talked to Dr. Hongwei Xin regarding the environmental impacts of different types and sizes of farms. He said that it's all about managing the manure - no matter the system.

 At Best Food Facts, we're not just here to talk about food in it's final form... you know, how it comes to you in the grocery store.



We're also here to explore how food is grown/raised, processed, packaged, researched, regulated, etc. That's why we dig into issues like how animals are raised, what animals eat, why hormones and antibiotics are used, what technologies are emerging and whether GMOs should be labeled.



Recently, we received an inquiry about the environmental impacts of manure from free-range chickens versus manure from chickens raised in barns. To answer the question, we enlisted the help of Dr. Hongwei Xin from Iowa State University, who was a featured expert on the Discovery Channel's Modern Marvels episode about eggs.



Dr. Hongwei Xin

    • Director, Egg Industry Center – http://www.ans.iastate.edu/EIC/
    • Professor, Agricultural & Biosystems Engineering (ABE) and Animal Science
    • ABE Associate Chair for Research


Best Food Facts: Thinking about the amount of manure that animals produce, it seems that farms that have a free-range system (where the birds can distribute their manure directly to the land), instead of large barns with thousands of birds (concentrated animal feeding operations - or CAFOs), are better for the environment. Is this true? 

Dr. Xin: "The answer to the question is 'not necessarily.' Here are the reasons:

1) "Free-range hens have a tendency to stay/forage in the vicinity of the barns/sheds that they return to at night. As a result, the distribution of manure and its nutrients in the soil can be rather skewed, i.e., more concentrated near the barns/sheds and much less in other parts of the pasture or open space.

2) "Manure application from CAFOs follows a comprehensive nutrient management plan or similar manure management plan. This means that the manure is tested for nutrient contents (N-Nitrogen, P-Phosphorous, K-Potassium) and the application rate is based on the manure nutrient contents, soil nutrient contents, and nutrient update needs of the crop to be grown. The application rate will be controlled so that the soil N or P threshold is not exceeded."


Best Food Facts: You mentioned comprehensive nutrient management plans, which are designed to make sure that the right amount of nutrients (in the form of nitrogen, phosphorous and potassium) from manure is applied – but doesn’t exceed the limits that the land can handle. What happens if a farmer has too much manure? What is done with it?

Dr. Xin: "Typically, farmers will sell their manure to certified manure applicators who have sufficient land to apply the manure on. Before a CAFO facility can be built, the farmer has to prove to the Department of Natural Resources (or equivalent state agency) that there is sufficient land to receive the manure generated from the CAFO facility."


Best Food Facts: What happens if the CNMP isn’t followed and too much manure is applied?

Dr. Xin: "If over-application is found, corrective actions will be taken, including fines for the farmer or the manure applicator, to ensure it doesn't happen again."


Editorial Note: The Center for Food Integrity, the sponsor of Best Food Facts, facilitates The Coalition for Sustainable Egg Supply (CSES). CSES is working to better understand the impact of various laying hen housing systems on a sustainable supply of eggs, including impacts on the environment. To do this, researchers at Michigan State University and the University of California-Davis are currently conducting a commercial-scale study of housing alternatives for egg-laying hens in the U.S. The first research flock was placed in April 2011. The study will be replicated over two flocks with conclusion in 2014 and results reporting to follow.


Have more questions about how manure is managed? Submit a question and let us know!


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