Of heat, pile reduction and microbs

subk3April 20, 2012

My motivation for composting is likely different than most of you here. Having a farm with horses one of the biggest stable management issues is how am I are going to deal with the stall waste. My biggest motivation for composting is reducing the size of the manure pile, that I get great compost for my gardens is an added bonus. (One I am very happy about, but really wasn't expecting to appreciate as much as I do!)

I use a a pelleted 100% pine bedding. It comes as an extruded pellet that fluffs up with the addition of water/urine. It's a little more expensive but it's nature being smaller than shavings but bigger than dust not only makes it easier to clean stalls but makes it amazingly fast to break down. My pile is a pretty consistent mix of manure, maybe a touch more pine bedding than manure, urine, (rubber mats and the absorption qualities of the bedding influences this) and a small amount of uneaten hay. The stuff practically evaporates. Again unlike most of you my problem isn't getting a hot pile, I'm wondering if my pile gets too hot!

I was talking to a commercial organic composter last week at a local garden show and he seemed to indicate that you might manage a pile differently if your goal is reduction as oppose to getting a quality finished compost product. I'm not sure, but I think he was suggesting that by not turning my piles often enough I'm killing the microbes. I thought you turned piles to introduce oxygen to heat the pile up!

Keeping in mind that my primary goals are a bit different, my compost mix is probably more consistent, and my quantities of compost material are significantly higher than most, could someone give me a little more insight on heat as it relates to microbes, pile reduction rate and management for outcome?

I'm not sure if I have an issue I should consider or if some sales guy was trying to infer my own results are inferior so I should buy some of his! (Which is so not happening!) I did drop some samples of my compost off today at the ag extension office for testing, so in a couple weeks I should know more about what it is I'm making, but I don't think they consider the microbes question.

Thoughts anyone?

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gardenfanatic(MO zone5b)

Sounds like you're making some good stuff!

I don't know the answer to your question, but my thought is that microbes probably need oxygen, particularly if they're aerobic. I'd probably want to turn the piles if it's not too much trouble just to make sure the stuff on the outside of the piles gets turned into the center so the weed seeds in the manure are ko'd.

But if you're pleased with your results, why change? If it ain't broke, don't fix it!


    Bookmark   April 20, 2012 at 7:17PM
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If the volume is decreasing and it's not reeking of anaerobic rotting I wouldn't worry about it.

With the pellets and the hay and the horse poo/pee - that stuff is coarse and full of fiber.

Hard to go truly anaerobic with it.

    Bookmark   April 20, 2012 at 8:29PM
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blazeaglory(10 SZ22/24 OC Ca)

Horse poopee

    Bookmark   April 20, 2012 at 10:12PM
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tropical_thought(San Francisco)

Actually turning the pile results in a heat lose. If you want to get a pile to heat up again after turning, you need more fresh greens and browns. I add more coffee grounds and more kellogs amend. So, I think turning more often would give you a cooler pile and maybe a faster pile reduction. On the other hand maybe a hotter piles makes reduction faster? What you want is to move the outer edges into the center, because they won't get enough heat. Only the middle will get very hot. But, if it just seems like too much work to turn it more. I agree with everyone else? Why bother to turn it? It will go away on it's own without much turning.

I think if it gets really hot the microbes would die, but they will come back when it cools down. The heat itself tends to create a fast reduction. It is as if the pile is melting away due to the heat. I don't know maybe some microbes can live in high heat. I guess this means this is something to research.

Maybe turning lowers the heat and therefore is good for microbes. Oxygen is good for microbes. Turning creates more oxygen for microbes.

    Bookmark   April 20, 2012 at 11:21PM
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blazeaglory(10 SZ22/24 OC Ca)

I have read that on average, to break down compost, it takes 3 days at 130deg (I think). So I would think turn every 3-5 days or so just to get everything mixed in real nice and keep an eye on the total "condition" of the pile. I would only turn my pile if I know it has been HOT for at least 3 days. I know this by inserting my hand deep into the center of my pile...lol

Pull out what you want to use when you need it as you see it composting the way you want it or when it is broken down into "mulch" or "top soil". Then again Im only dealing with a half full 120 gallon compost bin:-)

    Bookmark   April 21, 2012 at 12:22AM
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There are a number of reasons to turn a compost pile, just one of which is to introduce air. You would turn the pile if the internal temperature rose above about 160 degrees F, only because your compost is nearing spontaneous combustion temperatures. There are thermophilic bacteria that will raise the temperatures to that and beyond, if allowed.
You would turn you compost pile to be sure the material on the outside gets into the middle, where most of the bacterial activity is taking place, so it gets digested as well as the material in the center of the pile.
You might turn your compost pile if the material was too wet for the bacteria to work. Material in the compost pile that is too wet excludes the air the bacteria need to work.
You might turn your compost pile to allow you to add some moisture if it was too dry and the bacteria could not work.
You might turn your compost pile to introduce more material if necessary to aid digestion, ie. some source of Nitrogen if the bacteria are working too slowly or maybe some more carbonaceous material if there was too much Nitrogen initially.
I doubt that I would listen to anymore from that "commercial composter" given the much too simplistic answer he gave. By the way all compost is organic.

    Bookmark   April 21, 2012 at 7:24AM
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So how does heat (high or low) effect the rate of pile reduction?

How does heat and/or turing effect the make up of the finished product? In terms of microbes? In other words if you have two aged (say 2 years old) compost piles with identical raw material and one is turned often and one is turned sporadically if both have composted to the point you can't recognize the original material how will they differ from each other?

I was talking with the commercial composter while the DH was waiting for me outside the venue, so his "simplistic" seeming answers may be more a reflection of my lack of time and lack of knowledge on the subject matter.

Also while I know all compost is organic I meant it in the same way one would refer to "organic vegetables," a reflection of the growing process not whether vegetables themselves are organic or not. I got the impression from this guy that his process met the NOP standards for the compost to be used as such in organic gardening. (The standards require a rather involved composting process!) If "organic compost" is not the correct term what is the best way to refer to compost that has been managed according to the standards?

For those interested he was selling his finished product for $14 a bag. (Maybe a 30 pound bag.) I also suspect he provided a stall waste removal service for local stables so was also paid to acquire the raw material. Interesting business plan...

    Bookmark   April 21, 2012 at 1:34PM
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High temperatures is indicative of high microbe activity and a decent insulating factor. Heat itself does nothing. It is the very active (meaning lots and lots) thermophilic microbes that generate heat, it is a waste product as is CO2 and water vapour. The more bacteria present, the more heat waste generated, the more the material is consumed, the faster the pile shrinks.

Turning often may lead to some N gassing off but this has more to do with the C:N ratio than the turning. At the end, the difference is likely to be negligible. Turning may cause a brief temporary drop in temperature but this is usually recovered very quickly if all the other parameters are still in tolerance.

People often get confused when the term "organic" is thrown around. Crude oil is organic and water is a chemical. Context is everything.

NOP, as well as several other organisations, have standards. Very few backyard composters meet these standards. Having said that, few backyard composters deal with the materials that commercial size composters deal with so these standards err on the side of safety.

I tend to "dumb it down" when discussing composting with people until they indicate they are conversant with the process so I wouldn't read anything into a casual conversation.


    Bookmark   April 21, 2012 at 2:27PM
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All compost will be organic whether it is NOP certified or not. Keep in mind that NOP certified compost cannot be sold as "organic compost" in Europe since the standards they have are much stricter than what we have. Ours have been "dumbed down" to allow our major synthetic fertilizer companies to make and sell "compost".

    Bookmark   April 22, 2012 at 6:58AM
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bluegoat_gw(Zone 3b)

Lloyd has described it correctly. He has been paying attention to other posts on this forum. As more nitrogen is available, the larger the microbial population and the more heat is produced.

The breakdown of carbohydrates/glucose is given by the formula

C6H12O6 + O2 ---> CO2 + H2O + energy (ATP = chemical energy and heat energy)

and is the reverse of photosynthesis.

ATP is adenosine triphosphate and certainly worth reading about.

The glucose breakdown yields about 38 ATP or 262 kcal (38 ATP x 7.3 kcal/mol ATP). Glucose has 686 kcal/mol. Thus, the efficiency of glucose metabolism is 262/686 x 100 = 38%. Or in other words, about 62% of the energy is lost as heat.

When all the carbohydrates/carbon has been consumed by this process, the composting is finished. Just as a fire consumes all the carbohydrates leaving only ash, composting consumes all the carbohydrates leaving behind humic and non-humic substances.

Of course most composting efforts leave behind some carbohydrates. But the continued decomposition that happens in the soil is so slow that it has no detrimental affects on growing plants.

A carbohydrate ratio of 30:1 has been determined to be the optimum ration. This ratio is calculated on a dry weight basis. If you want to capture as many nutrients as possible the keep to this ratio or slightly above. If you want to reduce the pile as quickly as possible, then decrease this ratio.

Here is a link that might be useful: Adenosine triphosphate

    Bookmark   April 22, 2012 at 1:06PM
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Compost consists of organic matter but if an "organic certified grower" uses compost not made to standards they could lose their organic certification. It can make a difference to some. Like I said before, crude oil is 'organic' so it is important to understand the context/definition of how the word is used.


    Bookmark   April 22, 2012 at 2:06PM
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blazeaglory(10 SZ22/24 OC Ca)

And when you say a carbohydrate ratio of 30:1... to dumb it down that means 30 browns to every 1 green (so to speak) calculated from dry weight? In LAME MANS terms...lol

    Bookmark   April 23, 2012 at 1:32AM
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Thanks so much for the info! Bluegoat your equations are bringing back faint memories of a college biology class. I've gotten much fodder for googling! Although it seems the answers to some questions just make me think of more questions. It sounds like "compost" is actually a continuum. Lots of activity early then a slow reduction of activity until eventually it becomes humus. What are the (technical) indicators that identify when compost is "ready" for the garden or "done" and has become humus?

If the microbial activity is responsible for the heat how hot can a pile get before the heat is detrimental to either the composting and/or the welfare of the microbes? Do you want those microbes in the compost when you add it to soil? (that's what I think the compost producer guy was saying.)

Bedding horses on pellets is a relatively new thing. One of the big advantages is that when removing the manure from the stalls you generally remove about half the amount of pelleted bedding as you would if you were using shavings or straw. Since straight horse manure is generally around 20:1 to 25:1 adding less bedding helps keep the C:N ration closer to 30:1--thus much faster composting than with shavings or straw which shoots that ratio up. It sounds like the finish product might be better too.

I should be getting testing back on both 6 month and 24 month old compost samples (garden soil samples too) in another week. I figure the raw material mix of the compost won't change much if at all over time, so if I know my compost and I know my soil I can do a much, much better job of only adding to my garden soil what it may need that isn't provided by the compost.

    Bookmark   April 23, 2012 at 2:28AM
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"What are the (technical) indicators that identify when compost is "ready" for the garden or "done" and has become humus?"

Temperature is one, respiration is another. Non-technical indicators I've also used are the bag test and germination test.

"how hot can a pile get before the heat is detrimental to either the composting and/or the welfare of the microbes?"

160F is what most use for the upper limit. Anything above that and it begins to become fatal for most of the thermophilic bacteria. Adding "hot" compost to the soil isn't normal but if the soil has time to work on the material before planting it isn't a deal breaker.


    Bookmark   April 23, 2012 at 2:43AM
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I do not know what he was selling but my compost pile is never really turned. I will dig out a part of the center and switch the outside to the middle and put the dug out part back in.

I add products to speed the "composting" process, plus coffee grounds and old milk.

My pile which is chest height, when full, I am six feet tall, will be down to hip height by the next spring.

If I do not use all the leaves from my roses, I will then dig out the center put it into the garden and refill the pile, including climbing on top and jumping up and down to compact it so I can get all or near all the leaves in.

I can get away with this for two years before I have to empty the bin which is, I never actually measured it, apprx. seven feet, long by arm-pit high.

So IF- reducing size- is your main aim, adding some thing that speeds decomposition will work.

I have used it on and off for over thirty years and the difference is large.

    Bookmark   April 23, 2012 at 3:21AM
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