Occurence of Fecal Indicators and Pathogens in Composts

$0.00

An extensive study of quality of green-waste composts performed by Woods End and reported in the Journal of Food Protection, (Feb 2009), revealed surprising variation and levels of compost hygiene. Tested were market-ready composts from 94 facilities (CA, OR, WA) handling 4-million cubic yards annually. Detectable but highly variable levels were observed for E. coli, Listeria, Clostridium perfringens, fecal streptococci and only one case of Salmonella. Three samples were positive for E. coli-O157:H7, and in one case found to persist. High fecal bacteria persisted over time in 3 out of 5 retested facilities. Statistics revealed differences in relation to: annual volume, compost method, and compost maturity.

Applying hygiene thresholds (EU, ONORM and EPA503) indicated a similar number of composts would fail by any standard. The authors urge changes in the manner that composts are evaluated for quality: more research on how compost practices influence hygiene; re-evaluation of the relevancy of EPA’s Salmonella surrogate model; and enhanced safeguards for organic farming which relies mostly on composts. The authors suggest improved hygiene is achievable since “a large percentage of compost processors in this study were making product with a very low pathogen content”.