[USCC] Vol 29, #9--Regulation by various agencies

[frank]

David
(snip)

>I must conclude that averaging multiple temperature readings at a single
>location would provide better results than a single reading. It may take
>more time to collect temperature data at multiple depths, but it would
>definitely improve upon the current situation.  
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I think all we need is one high temperature in the center of the profile 
to show its working. As I see it, we want a moist, warm temperature to 
get the vegetative forms to develop then turn them in to cook. And 
repeat several times. We do not want to add a lot more layers to 
regulation. Taking center readings (or where it is most hot) along down 
the windrow and average readings the day the pile is turned  (directly 
after turning)  should be enough .

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>Part of the science behind the problems associated with composting biosolids
>should be determining the fates of the more recalcitrant materials that may
>be found in treated biosolids.  Even though many of the contaminant levels
>will be extremely low after secondary treatments, it is in the best interest
>of the biosolids composting industry to know that the materials they sell
>will not pose a significant threat to the health of people who use or come
>in contact with the end product.  If human health issues were not important,
>there would be no need for regulatory framework for the use and disposal of
>biosolids.  That is why I keep bringing up the issue of potential
>contaminants, so we don't lose track of the reasons for the analyses we do
>perform on composts and especially on biosolids compost.  I urge more
>stringent analytical testing.
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I disagree. Testing for potential contamients is a lot endless testing - 
and impossible. We need to look at known toxins and be ready to act when 
a new, previous unknown toxin shows its face.  Unfortunately to be a 
toxin it needs to first make someone sick, kill someone or be toxic in 
some way before its gets the name of 'toxin'. Thats just the way it is. 
Many of the organic reactions people on this list are concerned with is 
just the normal  biological degradation process that we want to happen. 
It happens and happens until the available carbon is used up and we have 
a stable compost - our goal.


>Reading the following literature it became evident to me that most
>time/temperature data come from research that examined the destruction of
>pathogens in the minimal amount of time, rather than focusing on the minimal
>temperature relative to the time required for pathogen kill.  The research
>in this document examined the temperature necessary to reduce pathogens ten
>fold (logarithmic reduction). Some research expressed in this document was
>based on pathogen reduction during biosolids composting that shows some
>pathogens can be killed effectively in short periods of time at even 121
>degrees C.  Keep in mind that this literature does not provide data on all
>of the organisms at all temperature regimes, but appears to show a potential
>for pathogen reduction even at 10 degrees below PFRP temperatures.  Also
>stated in this literature, ammonia, competition for resources by other
>microorganisms and resource availability play a significant role in pathogen
>reduction.  With additional research as you suggest, there is not reason to
>believe at this time that composting biosolids at lower temperatures for
>longer periods may not provide a more reasonable way to reduce pathogens
>without major reconstruction of the regulatory framework or the composting
>processes.  This concept is definitely worth a study or two. 
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Interesting. And I think what you say shows that temperature 
measurements are a better way to measure reduction of pathogens than 
fecal coliform. And once temperature requirements are met (whatever is 
decided) the windrow can be considered pathogen free to below risk 
levels and no more testing required. For example, ammonia seems to kill 
the fecal coliform in raw manures but I would not be surprised if the  
more resistant spore etc. forms are still viable.

Frank

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-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com