Actually watering may make the pile hotter. It takes quite a bit of moisture to get the pile going so NOT watering will make the pile cool. Since too much water makes it smell, just keep it turned and cut back on the moisture. But really I don't foresee a fire in your future but you could put the potatoes in there to bake for Memorial Day picnic.

See that's why a compost fire at the compost facilities is a pain.....the fire departmemt has to get the piles spread out before they can expect water to help the problem.

Aw, you're bragging...

A friend of mine recently offered to bring me several truckloads of mostly very old cow & horse manure that had been compacted on the floor of an old barn about 1 1/2 deep. This stuff was years old and with the exception of just a few fresh cowpies from one old cow that wandered in there occassionally it basically just looked like good dirt and we thought it was mostly composted. He hopped on the tractor and dragged all the stuff into a pile so we could load the truck. About a week later we came back to get another load and that stuff was literally smokin' when we dug into it (not steam, smoke) and it burned to touch it. I wish I had a thermometer with me. We were really surprised since it was so old and it was under roof so it's not like it was getting much moisture, if any. Granted it hadn't actually caught fire but I had always read it would need quite a bit of moisture to get to that point so I don't know if I trust doing that again in the future and leaving it unattended. We have since loaded the entire pile so it's no longer a potential fire risk but it was a little alarming.

Danielle

If it gets above 160 turn it. If you have any carbons you can add them. All in all good stuff. I doubt it will light a fire, but getting over 160 is not productive for the microbes, 120-160 is ideal.

Spontaneous combustion happens when an organic material has the right combination of Carbon, Nitrogen, moisture, and air and the digestion process reaches the ignition temperature of that material. 170 degrees is a ways away from that ignition temperature but is an indication that things are reaching toward that and you need to turn you pile and mix things up more. I don't think I would add any more Carbon which would just feed that heating up with more fuel, unless you added so much that the bacteria working did not have enough N to do that work.
That some people are very skeptible that a compost pile will spontaneously combust simply because they have not seen it when there are reports from all over the world of this happening indicates something, but I know woodworkers that do not believe rags and paper soaked with oils will spontaneously combust either.

I have had a pile catch fire, one time. I have kept hundreds of piles over the years and that is the only time I've had it happen. It was a large pile, yes. It was tree chipper material and I let it get to dry in parts while other parts were still moist enough to be "cooking".
Lots of people wish they could get their pile to 170. It will not catch fire unless it gets to dry. A turn would be good or just monitor the moisture.
Just a note that most of my material I mulch rather than compost. It's hugely more time and labor efficient. I still compost fresh manure with other materials, usually materials that are large, hard to break down, or potential weed problems. ex. palm fronds, date pits, bermuda grass, weeds with seeds, thorny things like bougainvillea.
Death to bermuda grass! ::smiles his jolly smile::

kimmsr, I am guilty as charged. I tend to be skeptical about many things until I can understand the principles behind it.
3rd hand information, "I had a friend who knew a guy who claimed he saw it happen" just doesn't cut it for me.

Now softmentor had it happen 1st hand, the elements for combustion in this case were small pieces of chipped wood, in a large pile that was thoroughly dry in some parts, while still composting in others. That kind of info I can use.
It tends to support my assertion that a small pile that is evenly wet is not going to be a problem. Note that softmentor experienced 1 fire in 200 piles and only because it was poorly tended.

Nevertheless, I am eager to read about other first hand experiences of compost fires and the conditions that led up to the fire.

If you're curious about details/conditions of compost fires, you can do a search (in the box in top right hand corner) for compost pile fires, kimmsr posted on a recent thread (april/may 08) that he was a (volunteer?) fireman that put out a few of these - and relayed the details of some of the conditions - interesting reading.

All the Best, Tree

I heard one believable compost fire story. A plastic bag of fresh cut grass clippings against a tree caught the tree on fire.

For my own composting, I try to run as hot (quick) as possible. My three compost thermometers read 10F apart, and I never got over 165F, so yours might be reading a bit high.

Compost fires are quite plausible. Around here, barn fires were common in the past if the hay was brought in (baled) before it had dried properly, as it would spontaneously combust. I've opened a few bales that were stinking hot, but that was before the age of the compost thermometer, so I don't know exactly how hot they were. When we were putting hay in the barn, we out-sorted the heaviest bales for immediate use, as they contained the most moisture.

Now, not too many compost piles reach the size of a full barn of hay, but if you insist on getting them as hot as possible, you might want to keep them away from combustable materials...

Cheers,

Tim

My .02:

Turn it, spread it out a bit, make sure it stays moist.

I had a pile 6 mos ago that was very hot-- 165* and one day I went to turn it and there was ash in the middle. It scared the crap out of me (it is against a wooden fence, 10 feet from my house). I now check the temp daily and when it hits 150*, I turn it. It cools it down a bit, as well as brings in the edges of the pile that can benefit from heating up. It then goes up again in a week or so, and I repeat when it gets to 150*.

Seriously, when you see *ash* and material you know is straw and garden waste that now looks like burned paper in the middle of your pile ---it is a bit frightening!!

arwmommy's experience is much more common than many here will admit to. I have seen some that write here attempt to explain the ash, known as "flash", in compost piles as being fungal activity. It is not and is the result of a rapid combustion that did not spread very far for some reason. It can happen if the moisture levels in the compost are not even.
There have been articles in the news for years about a compost pile spontaneously combusting but also I have been out to investigate a fire that started in a compost pile only to be told by a fellow investigator, who has no gardening experience, that there is no way the fire could be started by that source, that it must have been a child plating with matches. Only someone with very limited experience would discount spontaneous combustion in compost.

It would be almost impossible for a home compost pile to combust into flames. Temps under 300 degrees are not hot enough for a fire to start. Im almost 100% positive that no backyard composter has had their pile heat up that high.

As for the gray ashy stuff, karchita is correct. It is fungus hard at work decomposing.

Is this similar to what you've seen
{{gwi:285075}}

if so, its Fungus.

For the OP, your pile if functioning perfectly, I would suggest turning it once or twice a week for optimal results. Once the pile no long heats up you can back off on the turning frequency.

That is NOT what mine looked like. It looked like burned paper in the middle of the pile, with ash on the ends. (like burned paper looks like). I *rarely* agree with kimmsr, even if only for the usually snotty tone he/she writes with, (sorry kimmsr, it is true! And the same on organicgardening.com too) HOWEVER, since I have seen it with my own eyes, I will have to agree this time!

Believe in small compost fires or not, whatever, but if your pile is that hot (over 160*), the beneficial bacteria have died anyway, and it is to *your* advantage to turn it and cool it down and incorporate the edges of the pile into the middle. Get a full batch of compost faster-- who can argue with that? And the "are compost fires a reality?" won't nag in the back of your heat anyway!

JMHO.

From the University of Minnesota Extension:

"Questions sometimes arise about spontaneous combustion in compost piles. Spontaneous combustion is the occurrence of fire without the application of an external heat source and can be caused by chemical, biological, or physical processes. Organic material can ignite spontaneously due to biological activity at moisture contents between 26-46% moisture if the temperature exceeds 200 degrees F. These high temperatures only occur with restricted air flow and piles exceeding a height of seven feet. Spontaneous combustion happens to stored hay or silage and only in rare cases to compost. No documented cases of spontaneous combustion have been reported for compost piles smaller than seven feet. Most reported fires occurring in compost piles are the result of external sources such as matches or the addition of hot ashes. In short, a well maintained compost pile with temperatures less than 150 degrees F will not spontaneously combust. If a compost pile gets too hot--more than 160 degrees F--you can cool it down by 1) reducing the size of the pile; 2) adding water to 55% moisture; or 3) mixing in coarse, bulky material such as wood chips. Compost piles work best at temperatures between 130-150 degrees F."

Sue

Here is a link that might be useful: University of Minnesota Extension, compost combustion

belgianpup, you wrote "No documented cases of spontaneous combustion have been reported for compost piles smaller than seven feet."

As my pile is 4 ft or less, I will not worry.
I doubt that I will have the first fire in history.

Now, about that ash stuff in the middle of the compost pile.
I have always understood that if the pile gets too dry, a while powdery fire fang fungus takes over.

From CABI Bioscience I read "Fire fang destroys the compost when the pile once the compost becomes dry." Alternately, people making mushroom compost look for the fire fang to completely cover the compost.

As I have had great results using spent mushroom compost in my vegetable garden, I cannot resolve these two points of view. One thing that I can say is that dried leaves covered with powdery fire fang looks a lot like ashes.

My son-in-law manages a landscaping company. The owner of the company had a large amount of wood chips hauled to her property, and it was dumped in one large pile (12-15 feet high). It started burning after sitting there several days. My son-in-law said he never would have believed it if he hadn't seen it himself.

Deanna

Sorry, Deanna, but I don't see any connection between that event and whether or not a properly managed home compost pile can self-ignite. That is a completely different situation.

"No documented cases of spontaneous combustion have been reported for compost piles smaller than seven feet."

Anybody know how big esobofh's compost bin is? He had a fire and his bins looked smaller than 7 feet to me.

Rarely, if ever, will a properly managed compost pile ignite spontaneously and that is not what is being discussd here. Compost piles, just as any pile of any organic material, can spontaneously combust given all the right conditions. Thousands of people store hay every year and most of the time it does not spontaneously combust, but it can and will. I have been to barn fires that were caused by the spontaneous combustion of the stored hay as well as fires caused by the spontaneous combustion of compost piles.
The University of Minnesota people that wrote that did not look very far for information, but then again there is no place on the fire report for size of compost pile so that information is not out there and therefore the writter can state that "no documented cases have been reported" because that information is not included.
arwmommy, I am sorry you read what I write as "snotty" because that is not the way I write it.

Kimmsr,

**highjack**

What do you do? It sounds like you have a job as in investigator to perform RCA?

coolbythecoast,

If may be hard to believe a pile of wet materials may ignite, but how long do you think organic material would have to stay at 150+ temperatures before it dried out considerably? I can imagine a wet pile drying in the center, and igniting there - provided the temperature got above the flash point of the materials.

That's where this at first seems like an urban myth to me - paper's accepted average flashpoint is 451F (as Ray Bradbury has made us all aware) and I assume leaves and dry grasses must be at least above 400. It seems unlikely that anyone's compost can achieve that without drying and halting activity without very special circumstances and some help.

But what I wonder is if the ignition is of some form of gasses formed by the breakdown of OM itself. That would allow for both a lower flashpoint, and the existence of combustion in a wet environment. I'm just noodling here, but it's the only way spontaneous combustion in a compost pile makes sense to me, given the information I have in my tiny cranium.

Here is some information from the Washington State university site. It shows that spontaneous combustion can happen at temperatures much less that the 450degrees stated above. It's talking about hay, but shows that it can happen between 180-212 degrees if conditions are right. Will a "properly managed" compost pile ignite? Probably not, but it is possible with the right conditions in a pile of decomposing material.

Clip...
Spontaneous Combustion: how it happens
The process of spontaneous combustion involves both microbial growth and chemical changes and may be slow to develop. The wet hay will first stimulate microbial growth and as these organisms grow they produce heat while drying out the surrounding surfaces of the hay for energy. More drying surfaces produces more microbial growth and different types of microbes live and die as the internal bale temperature climbs.

When the bale temperature reaches about 150 Fº the hay is on a one-way street and going the wrong direction! The larger the haystack and the more densely packed the hay is the longer it may take to show signs of internal bale burning. Internal bale temperature may take several weeks before reaching 150 Fº, but from this point on more heat resistant bacteria, called exothermic bacteria, start a process of chemical change that rapidly increases temperatures to the point of spontaneous combustion.

What You Can or Must Do
When bale temperature rises to 150  160 Fº, it is time to take action now. (Fire is likely from 180 to 212 Fº.)
Clip...

Here is a link that might be useful: http://ext.wsu.edu/hay-combustion.html