eli5 How do waste(compost pile) ignite up without real fire touching them ?

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I have noticed smoke coming out of pile of waste without igniting them with fire, and it got me thinking, what is the science behind the phenomenon?

In: Mathematics

Compost is actively decomposing thanks to the bacteria and fungi inside it, which generate a lot of heat. That heat can build up, pushing water out and eventually get something within the pile to smolder and eventually burn.

Composting results in a lot of chemical reactions going on. These reactions result in a lot of heat being generated.

That said, that’s usually not smoke. It’s steam. While compost piles do get hot they are (supposed to be) really moist. It’s certainly possible for that to be smoke, and a compost pile can ignite, but that’s rare and means something has gone wrong.

Decomposing plant matter, metals rusting, candles burning are all forms of oxidation. Oxidation=fire

This also happens to hay barns if the hay isn’t dried out properly before being stored and once that goes it’s gone in a flash

I think there is a lot of speculation here. Compost does not spontaneously combust.

Microbes can not operate without moisture, and can not survive temps higher than 100 Celsius. Moisture does not exist past 100 Celsius either. Fire starts around 300 degrees. You still need a spark, and dry material, regardless of the act of composting.

I have composted at projects in the sub arctic, desert, and tropics, and have worked with hundreds more, none has ever experienced spontaneous combustion.

so do you think farmers near me may have damaged hay vales i could pick up and use for erosion control?