rot
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Finding Ash in the Compost

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I've seen a couple of posts now of people finding ash in the compost like the pile is getting too hot or something.

I've seen leaf mold in my hot bins before that looked an awful lot like ash but I've thought it a good thing.

Is anyone really getting ash in their hot compost bins or could it be more of an ashy like mold?
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Charlie MV
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I ran an entire chestnut tree and a hundred corn stalks through my chipper this summer. It made a pile a yard and a half in all directions. I hosed the layers 6 inches at a time. It burned my hand the next day and when I tossed it there was ash in the middle. Air temps were over a hundred but I think it would have done the same thing in the dead of winter. You need to consider spontaneous combustion in large well balanced piles.I think chipping it makes a difference too.

rot
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It was so hot ...

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I wonder what temperature combustion occurs?

I rarely accumulate that much material at once and my hot bins only amount to 17 cu ft. They sit out on a concrete deck away from most things so if I ever get combustion, I'll consider it an accomplishment.

Since ash is high pH (or is it low pH) and will smother things, I can see it as a problem. I've just never seen it except when mixing in stuff from the fireplace.
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rot,
I've seen leaf mold in my hot bins before that looked an awful lot like ash but I've thought it a good thing.

Is anyone really getting ash in their hot compost bins or could it be more of an ashy like mold?
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I'm with you on this. I too find a sooty, grey mold-like material in rotting plant material.
I wonder what temperature combustion occurs?
Did you ever read Ray Bradbury?
https://en.wikipedia.org/wiki/Fahrenheit_451
I wonder if it is possible the generate these temperatures in the relatively small piles we are dealing with.

Norm

Charlie MV
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Great point Norm. I read a couple of really crappy books lately. I'll toss a couple in my next hot pile to cool it down.

rot
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Too hot for me

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I was thinking of Fahrenheit 451 but that's for books. What about at a narrow point of surface with optimal oxygen levels? And do you need that much heat to produce ash?

I'm just thinking that 451 F represents a lot of heat for even a large compost pile under optimal conditions.

I suppose I better go research it. I'll have to convince my wife that we need a really big bin and I have to go out and get as much material as I can to fill it. Late spring ought to be a good time for that.
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wingdesigner
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Different materials have different flash points. (temps). I wouldn't locate a hot compost pile next to any structure or woodpile, just in case. (+25 years in insurance claims--It's not a matter of "if" but "when)

Hi Charlie MV!
Happy Gardening,
Wing

rot
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Seems a bit much for me

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I did a little lurking on the net.

Ignition temperatures:
wood 350 C 660 F (MSN Encarta)
wood 190-260 C 374-500 F (www.tcforensic.com.au)
hay 172 C 341 F
paper 218-246 C 424-474 F
leather 212C 413 F

The tcforensics site did also have one other interesting temperature range.

wood chars (30-50mm/hr) at 120-150 C or 248-302 F

Interesting but all those temperatures seem a bit extreme even in a large compost pile. In order to char wood, you're boiling water and then some. Might be a neat way to make charcoal though.

two cents
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cynthia_h
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A first-person article on fire prevention and safety at commercial compost operations:

https://www.jgpress.com/archives/_free/000326.html

A technical article about fires in large compost piles (Province of Alberta, Agriculture and Rural Development):

https://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex10721

A less technical but still informative article re. C:N ratios in common compost ingredients and the likelihood of spontaneous combustion (from the Univ. of Minnesota Extension):

https://www.extension.umn.edu/distribution/horticulture/components/3296-03.html

The consensus seems to be that piles over 165 deg. F need to be carefully broken down and cooled off to prevent the buildup of sufficient heat for spontaneous combustion.

My Internet search criteria were: "spontaneous combustion" + compost + temperature.

These were big piles; however, one of the articles recommends piles no higher than 7 feet. Another recommends piles no higher than 12 feet (using commercial equipment).

Cynthia H.
Sunset Zone 17, USDA Zone 9

cynthia_h
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Located a news source for last summer's fire at the City of Palo Alto (California) compost operation:

https://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/07/23/BA1311UPN6.DTL&tsp=1

The fire erupted approx. 5:15 p.m. (full daylight) on July 23, 2008.

Cynthia

wingdesigner
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Seven feet and 12 feet??!! Yikes! I should have that kind of space...besides, the not-so-friendly-but-ever-so-zealous city inspector would have us for lunch.
Happy Gardening,
Wing

cynthia_h
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Yeah, I can only dream, too. My Biostack bin (capacity not quite 1 cubic yard) is all I've got for compost, but it does its very best!

Cynthia

wingdesigner
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I have something called the "Earth Machine", purchased from a local garden club. Was so impressed I went back the next year and bought another. Pawned my old square one off on a friend up north. These are round, about 2.5' at the base and slightly tapering to the top at about 2', so nice and big to throw stuff in. Door at base to dig out finished compost. I did a no-no and located it under the eave of the garage to catch runoff so I don't have to use tap water. But it goes from raw to finished in less than a year. It rests during the winter, but starts right back up again in spring. One time I had hornets in it and had to nuke it, but no problems otherwise. I think there was another thread about someone who discovered fire ants in his. I hope someone came up with a solution, but he may have to do what I did and sacrifice a year to ornamentals only, and cycle through again before using it on edibles.

About those stacks, I can't imagine trying to manage something that big! No thanks!
Happy Gardening,
Wing

rot
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I walk the pile

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Thanks for the links. I'll be sure to walk on my piles everyday and monitor my huge 17 cu ft bins.

Cooking at 70 C (158 F) your hamburger is done and so is any gift from the dogs. Cooking at 75 C (167 F) and your chicken is done and so is any gift from the cats. There is a guy in our area that likes to demonstrate composting by cooking a chicken. If I could get those temperatures, I might get excited about hot composting again.

One of the comments on the SF Chronicle article said that what happens is that under the right conditions the pile goes anaerobic and starts generating methane and that's what starts the fire when enough heat is generated. That doesn't seem quite right to me but I don't know much about anaerobic bioreactors. I'd like to know more about that.

I noticed the UofW site referred to the Cornell site for ingredients which is the best list of ingredients I know at:
https://compost.css.cornell.edu/OnFarmHandbook/apa.taba1.html

The BioCycle article was good but they're talking huge facilities.

I never doubted that compost fires occur purely through the heat of the decomposition process. I've seen the occasional report in the paper and I can remember when the mushroom farm by the freeway smoldered for a couple of weeks along my commute. Decomposing hay in a barn loft is one of the competing theories for what started the great Chicago fire in the 19th century. I just don't see a backyard compost pile or bin getting too hot let alone that hot.

Water boils at 100 C (212 F) and if you're getting that then indeed the pile is sterile at least for a short time. With all the pathogen scares in nursery stock that might be a good thing. The fact of the matter is once the pile cools back down again you're going to get new microbial activity and decomposition is going to continue without doing anything. The way some people get weirded out by what they see as a health hazard in compost, it would be good to show them water boiling temperatures.

One of these days I'm going to have to build a 3 x 3 x 3 or better and build it up all at once and see if I can get 70 to 80 C. Just to see. Maybe I'll even turn it a couple of times.

Thank you for the new New Years Resolution: No 12 ft high compost piles.
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wingdesigner
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Just be careful, rot, or it'll start reeking, then you have a whole new set of troubles. Anaerobic compost piles are the cause of many a complaint to the local municipality and doesn't make for good neighbourliness (sp?).
Happy Gardening,
Wing

rot
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rotten messes

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Yeah wing, I've made some stinking rotten messes. There was the how many coffee grounds can I put in a bin experiment and there was the bins without covers in the rain incident.

I guess what I should have indicated was that I'd like to know about an enclosed anaerobic process in particular where the aim is to produce methane to burn like some pig farmers I heard about in China. That was largely a manure digestion process but I'm not entirely adverse to that. Mostly I'm curious. I don't have great sources of such ingredients so I'm really not in much of a position to pursue it unless I could use what the dogs give me. Do you just put manure in a trash barrel and bleed the methane out the tube on top or what? Does it need water? Do you ever change out the ingredients? Pathogens? I just don't know anything about the basic mechanics of such a process.

More of a passive interest than an active pursuit.
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2cents
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Re: Finding Ash in the Compost

[quote="rot"]..
I've seen a couple of posts now of people finding ash in the compost like the pile is getting too hot or something.

:arrow:

Some leaf piles of 2 plus yards have netted me large clumps of white/gray mold? I figure this is the real stuff/leaf mold?

More than a few years ago my dad got an idea to go to the local feed mill and compost corn cobs, lots of corn leaves and dry stalks in this.
We must have brought back more than 20 yards of this stuff(we were big gardeners)(he had 4 willing? strong helpers)(teen boys). It was a big pile.
This was placed on top of the old compost pile of 5 plus yards of stuff, well rotted.

That pile burned that year, we put it out several times.
It would smoke and smolder and yes it did catch fire.................. most of the time it was just hot, dad would have us put our hands in it and dig in it just to check out what was going on.
Dad figured out that we had to stop putting it out with water. So we would spead the smoking charred parts thin over that part of the lawn. It killed the grass.
We would keep the shovels right beside the pile.
But, we didn't turn our piles and dad told us not to, and not to play or dig in it. We had to stay away from it just so it could rest.
Of course the fire brigade, still had to be on the ready.
He started to use it in the garden, but it killed everything in that part of the garden that year.
The fire portion eventually stopped, but we watched it steam for a long time.
He didn't use it for 3-4 years after that.
YES compost can catch fire...mostly it steams...and it can smoke...and yes flames...believe me.
Do not compost just corn refuse in huge piles.
:shock:
IMHO

wingdesigner
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Pick your favourite search engine and type in "manure to methane conversion". You'll get tons of sites, but one of particular interest might be the one that uses aquatic plants.

I don't believe this can be done on a small scale. For a lighthearted look, there was a "Dirty Jobs" episode that showed a farm that made pots from manure, and recycled the rest of the poo into methane that powered the equipment. There was (either that episode or another) a segment on a retention pond for the urine that used some kind of algae to "process" it.
Happy Gardening,
Wing

rot
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thanks for the tip

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Wingdesigner,

Thanks for the search tip wingdesigner. Too many to digest right this moment.

Maybe I will add something like 'dog something or other' to the search to narrow it down a bit. We've got four dogs and that seems to amount to something.

If I remember the 'Dirty Jobs' episode, they were squeezing out the moisture content and then baking for the pots. I don't think I want to get that labor intensive with that kind of, well, ingredient.

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2cents,

I have seen ash like stuff with lots of leaves and presume it to be a leaf mold like some of the leaf piles I let lay. My temps rarely get over 150 f.

I also have a new New Year's Resolution: Do not compost just corn refuse in huge piles.
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