Environmental Benefits of Composting (continued)

Heavy Metals/Human Pathogens
The presence of heavy metals and human pathogens in compost and vermicompost is an important issue for discussion. It seems widely accepted that pathogens are destroyed by the hot composting process, although materials such as cat, dog, and human feces are not recommended as ingredients in residential composting systems in the United States, as some of the pathogens present in these materials are still viable even at extremely high temperatures. Biosolids composting is a field in and of itself which has many regulatory controls. It is noteworthy that a key to pathogen control in compost is compost maturity, as some pathogens naturally live longer then others. Vermicomposting never involves temperatures as those achieved with hot composting. For this reason, one should never add cat and dog feces to residential vermicomposting systems, with one exceptions: if the system is designated for dog and cat waste only, is not handled by pregnant or immunosuppressed persons, and if the digested contents of the bin are to be applied to nonedible crops only. It is crucial that anyone in contact with a worm bin used to handle pet wastes that carry human pathogens be informed of the risks involved. With vermicomposting the high temperatures necessary to kill human pathogens cannot be tolerated by earthworms. For this reason, one should not add cat and dog feces to most residential vermicomposting systems. They may be added to specially dedicated worm bin systems like the Tumbleweed Pet Poo Converter, but the resulting castings are recommended for use around non-food plants only. Otherwise, worm castings are even safer than compost for food plants. This has to do with the fact that, again, the enzymes in earthworms’ bodies break down organics such an extent that toxins are actually fixed in the soil and are not readily metabolized by plants.

The above is also true with regard to heavy metals. Earthworms are quite sensitive to toxins in their environment and their appearance and behavior are indicators of their health. If your worms seem healthy, continue what you are doing, but to be absolutely sure of the safety of worm castings have them tested at a soil lab.

Related Articles
Scott Greytak, Clive Edwards and Norman Arancon. Effects Of Vermicompost Teas On Plant Growth And Disease, BioCycle Magazine,Saturday, 19 August 2006. View at: http://www.wormdigest.org/content/view/311/2/

Bruce R. Eastman. Spiking the Biosolids. Achieving Pathogen Stabilization Using Vermicomposting. BioCycle Magazine (November 1999, Page 62). View at: http://www.p2pays.org/compost/Vermicomposting/Achieving%20Pathogen%20Stabilization%20Using%20Vermicomposting.htm

Velugubantla Adinarayana and Sukruth T. Kumar. Acharya N.G. Ranga Agricultural Univ, Rajendranagar, Hyderabad, India. Effect of Applied Phosphorus and Vermicompost on Removal of Heavy Metals by Leafy Vegetables in Polluted Soil. Presented on Monday, 07/10/06 at the 18th World Congress of Soil Science - Philadelphia, Pennsylvania. View at: http://www.ldd.go.th/18wcss/techprogram/P15743.htm

Compost Organisms

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