Compost heap safety

[grenfell]

I've a number of customers that I visit once a fortnight and went to see one this week. The job she wanted me to do was to take down the compost heap , it was one of those pallets nailed together type of things. She'd read or heard that during the recent hot spell some of the fires had originated in compost heaps. Now I know heaps get warm and have put milk bottles of water in them to heat up and the water has been hot enough to do the washing up for instance but hadn't heard the reports regarding the fires. I suppose there must be an element of truth in it , I've seen large heaps smouldering on farms but began thinking that there must be some sort of relationship to size. The heap I dismantled was less than a cubic metre and wasn't particularly warm. The other factor must be what goes onto the heap. The one I dismantled seemed to have a lot of wood in it , some of it looked to be chippings from a chainsaw and there were quite a few bits of wood such as tongue and groove boarding that hadn't really decomposed. There was also bits of fence panel and even some treated decking board I doubt most small heaps get hot enough to start a fire but just something to log in the back of my mind.

[Le Mouse]

I did see photos on Twitter from someone whose green bin (garden waste) had gone up on the Tuesday and taken out the fence next to it. I suppose being constrained by a plastic bin, it would have got hotter. Quite scary!

[jansman]

Not something I have come across either, and I have a good number of heaps - and for many years. Still, it’s a heads - up, and not to be dismissed, for sure. The biggest hazard I have experienced with a heap is rats. But that’s another issue…

[jennyjj01]

I doubt most small heaps get hot enough to start a fire but just something to log in the back of my mind.

I keep a soil thermometer in one of mine. Highest recorded temperature was 65C which was pretty hot, but I couldn't imagine it catching light. Maybe a bottle left lying around could do so, but it's quite a stretch.

[grenfell]

It would be interest to know what the temperature was when we hit the high 30's and into the 40's and compare that with times of more normal temperatures. I would expect the internal temperature to be slightly higher in hot weather as heat is slower to wick away but I can't imagine it getting hot enough to combust. A google says something like 300°C for dry grass and 233 for paper and 227 for peat
http://www.tayloredge.com/reference/Sci ... ition.html

[Frnc]

Give it a turn and a bit of water, should be ok. I looked at the one I bought on Amazon. 4000 reviews, none mention fire.

[jansman]

I’ve never known a fire. However, even in the highest heat- weather - I was still digging worms for fishing. Worms won’t stand too high a heat. Just my take on the matter.

[jennyjj01]

I’ve never known a fire. However, even in the highest heat- weather - I was still digging worms for fishing. Worms won’t stand too high a heat. Just my take on the matter.

Worms and insects would surely cook at 100C and for the temp to get above 100, all moisture would need to have been driven off.
The 300C to get fire seems, surely, way beyond the heat generated by decomposition. So it must need sustained full sunlight.

But The man on the internet says it CAN happen.
https://backyardsidekick.com/can-compos ... ost-fires/
https://composthq.com/composting/can-co ... rt-a-fire/

[Frnc]

It's a mystery. Maybe these fires start with sunlight being focussed on a spot by something. I heared about railway sleepers catching fire the other day. Of course forests catch fire quite regularly. Obviously the temp these heaps get to is way below ignition temp of paper or methane.

[Ahastyatom]

I mention this to a colleague who said that theirs cought fire. It was also one of those plastic darlik things, I wonder if they are more at risk.

Found this from 2012

https://www.google.com/amp/s/www.dailym ... lames.html

So seams rare but possible.