Why does garden waste steam?

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Offline rhade

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Why does garden waste steam?
« on: 11/12/2008 13:24:01 »
It has been very cold and frosty at nights lately, as many of you will have noticed. The other morning, I noticed my garden waste bin was steaming, but not my other two wheelie bins (the grey one for none-recyclable household waste and the blue one for recyclable household waste). Why was only the garden waste steaming?
As the great man said, "love your neighbour as you would love yourself- But first be able to love yourself."

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Offline dentstudent

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Why does garden waste steam?
« Reply #1 on: 11/12/2008 13:40:43 »
Short but sweet: Your garden waste is composting, decomposing the vegetable matter. This produces heat and what you see is actually steam.

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lyner

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Why does garden waste steam?
« Reply #2 on: 11/12/2008 17:56:18 »
And the warmer it gets, the faster the decomposition - so the warmer still it can get.
It used to be claimed that hayricks can set themselves on fire or this reason - but I don't believe it; the organisms couldn't survive above about 70 Celcius.

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Offline rhade

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Why does garden waste steam?
« Reply #3 on: 17/12/2008 13:31:06 »
Brilliant! I knew the answer would be something like that. I ought to know, really. It was bubbling under the surface of my consciousness and not quite getting there.
I think the hayricks one may be true. I'm pretty certain I've heard an explanation of why it does reach the required temperature. Unfortunately, once again, that one is failing to emerge from the Stygian depths of my memory.
As the great man said, "love your neighbour as you would love yourself- But first be able to love yourself."

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Offline Bored chemist

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Why does garden waste steam?
« Reply #4 on: 17/12/2008 18:35:09 »
And the warmer it gets, the faster the decomposition - so the warmer still it can get.
It used to be claimed that hayricks can set themselves on fire or this reason - but I don't believe it; the organisms couldn't survive above about 70 Celcius.
Once they are hot enough so called "auto-oxidation" takes over and continues the heating. Haystacks can catch fire from this. So can oily rags and such.
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lyner

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Why does garden waste steam?
« Reply #5 on: 17/12/2008 22:46:22 »
Quote
so called "auto-oxidation" takes over
I, of course, believe you but when does the concept of activation energy apply?
Or is that idea an over-simplification?