I gather there is a debate about the safety of compost teas, particularly with respect to E. coli content in teas that contain, or derive from, manure. Some writings I've seen to the effect that E. coli should not be a problem in aerobic teas confuse me at the moment. As a group, E. coli is facultative anaerobic, which means that it can grow with or without oxygen. I believe the go of the argument is that other organisms repress E. coli populations by out-competing it in well-conditioned aerobic teas. I'd like to see some data on that. I've seen the suggestion (below) that restricting the simple sugar content of compost/teas can or does limit/help limit E. coli propagation. I suspect that this is along the same line as the idea that feeding cattle less grain reduces the presence of E. coli O157:H7.
I know that there are temperature sensitive phenotypes in the E. coli genome, but the growth curve of "typical" E. coli apparently drops off rapidly from about 42 C. As such, is seems to me that high compost temperatures would eliminate E. coli populations in the feedstock. Given the interest in the subject, I imagine all of these questions are answered somewhere, so feel free to chime in. I can't say that I'm very worried about it, but there it is.
The topice doesn't seem likely to vanish immediately. Here's a recent piece about the E. coli issue from http://www.woodsend.org
"A Compost Tea Task Force has been formed under USDA's NOP to examine potential risks of pathogen content in prepared compost teas. The Task Force will consider if new specific rules and guidelines are required to assure public safety for organic farming. The Task Force will look at various compost tea technologies, comparing US and traditional European approaches. "Certainly one hope in this process is that it NOT result in excessive new regulations" said Brinton, of Woods End. One scenario the committees will examine is "use-control", analogous to set-back provisions of pesticide use- potentially necessary to make certain that teas are not applied to readily harvestable plant portions. Brinton and Ingham, both members of the Task Force, have shown that various tea methods properly managed do not result in E. coli present in the final extract, the primary concern of the committee. Enormous concerns centered on use of sugars in the fermentation process to grow bacteria rapidly. Compost Tea manufacturers in the US have recently removed molasses from some brews.
An environmental agency observer of the progress of the Task Force commented, "it is important to keep a perspective on this, since we don't want to result in compost teas being mandatorily sterilized whereby all disease suppressive qualities will be lost". The USDA NOP process will incorporate the recommendations of the Task Force, expected later in the year."