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Testing Compost for Pathogens


November 6, 2012

I am searching for someone who can test my compost for E. Coli and Salmonella before it goes into my vegetable garden. Is this something you can help me with?


Answer by JE: I’ve been giving your email a lot of thought and I would refer you to environmental labs if your feel this is what you want to do compost testing. Just look under laboratories/environmental in the yellow pages or you can contact Universities that have an agricultural department such as NMSU. However, I feel an obligation to provide you with some further advice before you go through the expense of testing the soil. First you should ask yourself why you want to test for these organisms. Did you have some sort of contamination that you are worried about?

* Testing soil is very tricky and can be expensive. First you need to consider how are you going to sample it to make sure you get a true sample and not just a pocket. A good lab will provide you will detailed instructions. When I worked as a microbiologist, we would always say the test in only as good as the sample. If you don’t sample and transport it correctly the results are worthless.

* E. Coli is a huge family of bacteria and not all E. Coli is pathogenic (disease causing). All mammals have E. Coli in our GI system as they provide us vitamins and have other essential roles. They are a part of the “natural flora” of our GI system. Also E. Coli can be found in almost all dirt samples. If I tested a 100 shoes for E. Coli I bet everyone will be positive but very few will be shiga-toxin producing (this one cause the most trouble in GI problems) As an aside, E. Coli is the number one organism in urinary tract infections but are usually from the person’s own GI tract not from other sources.

* Salmonella is a water loving organism so you can save yourself a lot of money from testing by just letting your compost dry out completely for several months.

* Also if you are doing hot composting, any pathogens present will be destroyed by the heat. Pathogens do best at body temperature and will die above 120 degrees F. In addition, most pathogens can’t stand UV light so if you are in a place with lot of sun light it will also destroy pathogens.

Answer by JH: Here is a local lab that might perform the requested testing. If not they would know which local labs offer the service:

Geo Test Inc.
8528 Calle Alameda NE
Albuquerque, NM 87113

Their advertising indicates they perform soil and material testing & environmental services

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