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PostPosted: Fri Jul 04, 2003 7:50 pm 
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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."

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Last edited by Enzyme11 on Sat Jul 05, 2003 7:35 am, edited 1 time in total.

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PostPosted: Sat Jul 05, 2003 1:47 am 
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I think Dr Ingham makes a few good points in her monthly newsletters.

1. Compost isn't compost unless it's finished cooking. When good compost is finished cooking according to the commonly accepted industrial and governmentally approved practices, the pathogen count is zero per ton (undetectable) as determined by required weekly testing. The way it gets there is it spends 15 days minimum cooking at temps above 130 degrees F minimum. If you're using good compost, the pathogen count is zero going into the tea and will be zero coming out of the tea unless it is introduced from other sources.

2. Molasses stimulates reproduction of microbes in tea. When tea temps are in the 60s, the microbes can use the boost from the molasses to reproduce faster. The oxygen content of 60 degree tea can absorb the increased microbial numbers. When the temps rise into the 70s, the microbes are stimulated enough without molasses so cut back on it. When the temps rise into the 80s, a molasses stimulation will create a microbial bloom that will exhaust all the available oxygen in the water no matter how many aerators you have in it. Water will hold only so much oxygen at certain temps no matter how much air is pumped into it. If the microbes number enough, they can absorb enough of the available oxygen to let the anerobic microbes start to take over the tea. But once again, if there was no E. coli in the original compost, it will not spontaneously appear just because the tea goes anerobic.

The issue arose when a researcher published a report concluding that compost tea could harbor and promote E. coli. The report was enough to basically put compost tea on probation until the issue was resolved. Dr Ingham has reviewed the research and concluded that the tea started out with unfinished compost and was brewed in anerobic conditions according to the methods and temperatures published in the report. The original researcher replied with something to the effect of, "oh yeah!? Sez who?" So that sparked the controversy and hence the commission to investigate.

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PostPosted: Sat Jul 05, 2003 7:31 am 
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Dchall_San_Antonio wrote:
Water will hold only so much oxygen at certain temps no matter how much air is pumped into it. If the microbes number enough, they can absorb enough of the available oxygen to let the anerobic microbes start to take over the tea. But once again, if there was no E. coli in the original compost, it will not spontaneously appear just because the tea goes anerobic.

The issue arose when a researcher published a report concluding that compost tea could harbor and promote E. coli. The report was enough to basically put compost tea on probation until the issue was resolved. Dr Ingham has reviewed the research and concluded that the tea started out with unfinished compost and was brewed in anerobic conditions according to the methods and temperatures published in the report.


Yes, of course that's right about the temperature sensitivity of water's O2 carrying capacity. In addition, the difference between 60 F and 80 F implies an approximate doubling of the enzyme activity, which contributes/drives the microbial bloom. I don't have much doubt that the test tea was from unfinished compost -- E. coli cannot survive 130 F temperatures for an extended period. Probably only thermophiles (of which there probably aren't any/many in the typical feedstock) and spores can survive at that temperature. Lest anyone reading this be confused, E. coli can live quite well in aerobic conditions, so the aerobic/anaerobic debate really comes down to the issue of population density.

We could eliminate the E. coli issue by switching to poultry manure, but then there would be squawking about salmonella and campylobacter. As David wrote, E. coli doesn't (usually) fall out of the sky, so if it isn't in the compost, it won't be in the tea unless a raw manure product is added at the end. Even if it was, I personally would be concerned only with O157:H7, and then only a little. Just use common sense, and don't mistake compost tea for soy sauce.

I'm confident that the review will exonerate compost tea, but I think the whole matter illustrates a bias. There doesn't seem to be much hand wringing when, or over the fact that, pesticides or toxics in general are used in manners inconsistent with directions or "guidelines." The USDA and company sure seem to treat similar indiscretions in the organic world harshly by comparison. If Monsanto produced/sold compost tea, I doubt we'd hear a peep about potential pathogens.

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PostPosted: Mon Jul 07, 2003 8:45 am 
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I am constantly learning better ways to make great aerobic teas. Making aerobic teas is definitely more of a challenge, skill, and an art, than just making tons of hot aerobic compost piles. My compost is about 75% horse manure/sawdust, and 25% leaves, grass clippings, and food scraps.


As Dave hall stated from Dr. Ingham's work, if you start with good mature aerobic compost, there is absolutely no chance of spreading any diseases or toxins into your aerated tea brew. I'm learning how to get my teas to have more of a thick foamy top layer and that pleasant smelling, yeasty, or wine smell. This is the classic measurement, without going through an elaborate expensive tea analysis test, to determine if you are making great high fungal teas.

The challange is to make a good fungal tea. Any ole bacterial tea is easy to make, because they naturally outnumber fungi populations anyway. I can make good aerobic bacterial teas using my horse manure compost, dry molasses and grain cattle feeds. To make better fungal teas I have to use more mature well aged compost, more leaf mold, forest dirt, corn meal, rotten fruit less citrus fruits of course, or seaweed.

Beneficial fungi can digest more complex diseases and toxins better and faster than aerobic bacteria in a tea liquid solution.

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