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Composting Huge Amounts of Manure and Composting With Worms


September 13, 2013

We are starting a project in a Mexican border village where we work. Local stockyards generate 400 to 500 cubic yards of manure per year. We want to compost the manure for use on gardens and orchards. We want to feed some of the manure to red worms to produce castings to further improve the soil. The local soil is an ancient sea bed and is a salty mix of clay and sand. My questions: (1) What is the best way to compost large amounts of cow manure? (2) How do I know when it is safe to put on gardens? (3) Worm castings, I want to produce about 50 to 75 cubic yards per year. How do I do that? A final note on biochar made from pecan shells. We add it to our gardens at a rate of about 1 pound per square foot. It seems to have good results with the 50 or so gardens we have put it on.


Answer by JZ: It’s good to learn of your excellent project!
1. CAFO manure and mixed-in urine would be a high nitrogen material, you could add an equal volume / weight of a carbon eg. wood chips, straw, shredded cardboard / paper, saw dust, dried leaves. There might be a local municipality which has wood chips easily available(?). If this is a big operation you may need a front-end loader. You could set up wind rows and do a “hot” composting process.
2. You need to find out what (all) medications are being given to the animals. Metabolites may end up in the urine and manure. Once determined, you would need to research how these particular meds are biodegraded. There are a few broad leaf herbicides eg. Picrolam and Aminopyralid that may get into the food stream of the animals, if the hay / alfalfa have been sprayed by the farmers that grow them. All that you can do is inquire if the farmer used them. They persist thru the animals gut and the composting process, then may contaminate the compost. This is a long shot, but you should be aware of the possibility.
3. CAFO animals may be fed salt, which may end up in the manure and in the compost end product. Our desert soil is already “salty”, so you would have to test the end product for percentage salt before adding to garden soil.
4. Organic material that has gone thru a hot composting process should be screened and set aside to cure for at least one month. This is the cold phase of the process which finalizes the production of humus. Then you could take samples of the finished product for lab testing for salt, residual meds, etc. There are labs that do this type of testing.
5. I do not have expertise in large scale worm composting, but I think that in your area a requirement will be be a set up that protects the worm bedding from temperatures that exceed 80F. Your set up would need to designed for easy harvesting of the castings. There is expertise out there on large red worm harvesting. You will eventually find it.
6. Some local worms farmers are listed under Worm Sources in our website menu under Resources. You might contact them and then do a site visit.
7. The magazine “BioCycle” ( is a publication which has articles that would be of help to you.
8. Yes, biochar is an excellent bacterial growth stimulator.
9. You could take the compost facility operators course coming up in Oct.:
This course is repeated a few times per year. You would meet a many people who are involved in large scale composting in NM. Good place to network.

Please let me know if this has been of help to you. You are welcome to phone me after 7PM. This is a long discussion. There are many variables that could be discussed. You have an excellent idea. Keep up.

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