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30/08/2012 at 19:59

I had a compost bin which exploded, it was the  green drum type that you roll over and over to mix the grass, cuttings etc,  we heard a huge bang  and when we went outside it was blazing away and had completely exploded, the only thing I had done differently that in previous years was to put some charcoal on it after burning some wood and leaving it for a few days to go cold I added it to the compost.

30/08/2012 at 23:34

Sizeyuk1, you had by the sound of it a bomb. As a lad before elf and safety we did chemistry and were taught among other things to make gunpowder and our own fire works, Charcoal is Carbon, Nitrate in some fertiliser is Saltpetre, and Sulphur also present in some fertiliser and you have a crude gunpowder. Put that lot into a sealed container  with heat inside and out and a build up of Methane gas pressure given off by rotting compost I would stand well clear.
None of us really know what we tip into our compost although I never did trust any of those seal and turn containers, I have wooden open lattice types that let air in and pressure out.
Having been on an army explosives course you realise just how easy it is to make things go bang with normal everyday ingredients.
frank.

31/08/2012 at 09:23

As an retired fire underwriter for one of the large Insurance companies, I am fascinated by incidents like this. I also use peat compost and have a plastic pollytunnel. To have a fire you basically need 3 things – fuel, oxygen and either a heat source at or above the fuels flash point or in respect of spontaneous combustion - a temperature at or above it's auto ignition point. The flash point of peat is 225 degrees C or 437 F and the auto ignition point is 260 degrees C or 500 F. The hottest temperature I have recorded in my pollytunnel this year is 45 degrees C or 113 F. Unfortunately, like UFO mysteries, you will probably never know what really happened.

31/08/2012 at 10:09

Martin, it does interest me, I like to know what happened.
As an engineer at ICI we had chemicals, pressure, and highly inflammable compounds, every man and woman on the site had to attend the on site Fire Station for an up date each year which included fighting some sort of fire. The lads knew me so I usually got the bad one, often as I worked forward knowing the fire behind me was out it would self ignite from the heat of the surface it was on. Most of the explosions we had were pressure causing the initial blast then some outside element firing it up.
Rotting vegetation gives off methane which is why an open compost bin is better than a closed one it also depends on where it is full sun or shade.
Having lived in a house that used peat for fires you find it takes a while to fire up which was why we damped them down at night rather than let them go out.
The posters on here had a problem without cause, one a peat fire one an explosion, it would shake them and be a mystery but as you will know there is always an explanation, and as soon as Ash or carbon was added the light started to come on for me, we had to be very careful about the storage of Nitrates, which end up in most fertilizers.

Frank.

31/08/2012 at 10:20
Blimey. I use those plastic dalek bins and sometimes put in the ash from my wood burning stove. Should I start wearing a hard hat?
31/08/2012 at 13:44

Palaisglide - Frank, good post. Every fire has a cause, the loss adjusters had much more interesting jobs than us underwriters. There was an assumption that the fire started inside the greenhouse. Logic would suggest it didn't.

Martin

31/08/2012 at 14:15
figrat wrote (see)
Blimey. I use those plastic dalek bins and sometimes put in the ash from my wood burning stove. Should I start wearing a hard hat?

I would sugest the whole outfit as in The film the Hurt Locker.
As long as it is ventilated and has an opening for gas to escape they will work quite well. If it has a lid make sure it is loose fitting and any vents clear of debris.
Let me loose in your kitchen and from the cupboards I can make Phosgene gas explosive and poisons, dangerous places kitchens.

Frank.

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