Can a pile of fresh wood chips spontaneously combust?

[turnkey4099]

our fresh piles of wood chips, one large utility truck's worth (maybe 5'tall, 8'wide, 12' long) would smoke, and be uncomfortably hot inside. This in a mild climate, with plenty of water, and never covered.

I don't think you'd need too many variables 'worse' to get ignition: significantly hotter, drier days (it never got above 90, and had humidity), perhaps a perfect balance of material & moisture in the pile, etc. Or especially a pile twice the size.

For oddity. Highway department used ground up tires as fill over a culvert. About a year later it ignited. Washington state som 30 years ago but I don't recallthe location.

 

[mapper]

For oddity. Highway department used ground up tires as fill over a culvert. About a year later it ignited. Washington state som 30 years ago but I don't recallthe location.

Near Ilwaco, on the Columbia river. Deep mucky moist soil. It was determined that the steel wire in the rubber was the cause of the spontaneous ignition. Took a long time to put it out.
It was an experiment in use of tire chips as light weight fill in unstable soils, oops! That didn't work out so well.
A better result in light weight fill was in Seattle on the I90 and SR99 interchange near the stadiums, used giant ecoblocks made of styrofoam for all the ramp structures. Hasn't failed or caught fire yet.......

 

[oosik]

I really question if a pile of chips can retain sufficient internal heat to cause combustion. A pile of sawdust - completely different animal. A pile of sawdust is much more like baled hay in a stack.

 

[mikester]

I really question if a pile of chips can retain sufficient internal heat to cause combustion. A pile of sawdust - completely different animal. A pile of sawdust is much more like baled hay in a stack.

I just moved a large pile of forestry mulcher chips mixed with soil...steaming like crazy. Surprised me. Not small chips and no greens.

 

[rademamj1]

I will say this observation, as my chipper knives dull, the output bin gets finer and finer particles, more like a saw dust. I would not take a chance on large chipper piles, with a high content of small chip particles, doing a spontaneous combustion. Spread that pile to reduce risk.

 

[LouNY]

The process of composting is a heat generator. Most piles of composting materials will "steam" when dug open
as the warmed moisture is released to the atmosphere. Very few piles of composting materials will reach the temperature
required for combustion. They can be too hot to hold or shove your hand in but will be a few hundred degrees from combusting.
You will find it very difficult to hold your hand in a material that's over 110 degree F, but that is still a couple of hundred degrees from combusting.

 

[Bill Guenthner]

Can a pile of fresh wood chips spontaneously combust? Pile would be maybe 5 ft high by 10 ft diameter and be mostly all spruce branches with maybe 15% greenery. I can't imagine it happenning but I plan to leave the piles deep in a row of shelter trees and get them out in the spring and don't need any drama.

Seems like spontaneous combustion is an urban legend or is there a degree of truth in this?

This is a very simple equation. If having it catch on fire where it is would be a catastrophe then either move it to open ground or spread it out so it’s about a foot thick. There is a non-zero chance that it could catch on fire the way you have it now.

 

[BravoXray]

In the last few years we have had chip piles at three different mulch companies in the area catch fire. One on the south side of town had caught fire a couple of times, and they finally had to close up the business and get rid of the piles of mulch. Same thing happend to the one across from the NS Elkhart yard. One that was a few miles north of me burned for over a week before they got it put out.

 

[rademamj1]

From what I understand, initially the methane gas generated by decompose is what catches fire. More importantly, piles with large chip particles, usually allow the methane to ventilate to the atmosphere. Smaller particle sizes and poorly sorted wood piles can seal methane and incur higher risk for combustion.

Locally, I know of 3 fires related to large sawdust piles, associated with mobile home manufacturers.

 

[4570Man]

In theory it’s possible but it would take a massive pile for that to actually happen. I’ve had a tree guy dumping chips and I’ve never had a pile catch on fire or even smoke. They won’t burn very good when set on fire.