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Fire safety management of compost piles

Why do fires occur in compost piles?

Compost piles generate heat, and if this is prevented from escaping it can build up and the pile ignite. With the large amount of combustible material in a pile, there is high potential for a fire to develop unseen and to spread.

Fires in compost piles are most commonly caused when the pile:

  • Is too big
  • Is too dry
  • Has limited absorbency (does not allow moisture into the pile, so there is no cooling effect)

How to prevent fires in compost piles

Control the pile size

This allows more of the generated heat to escape and prevent it becoming trapped and building up excessively. Aim to:

  • maximise the surface area of the pile by arranging the compost in narrower piles
  • keep the pile depth to six feet or less
  • ensure access for plant machinery into the pile is possible should it be required.

For longer term management, determine how frequently compost needs to be removed to allow the piles to be managed and kept to a suitable size.

Monitor the pile weekly

Check the pile each week with a temperature probe to identify potential hot spots early.

If necessary, take remedial action to prevent the temperature reaching the 70-80ºC range where suitable conditions for self-ignition may occur.

Where temperatures are found to be getting too high, determine the size of the area affected and turn the compost over to allow the heat to escape. Use a hose to spray water directly onto the heated compost as it is exposed to cool it down and prevent ignition or further spread.

If temperatures are in excess of 80ºC and the overheated area is too large for you to deal with, the pile may ignite. If you cannot deal with it in a safe way and without putting yourself at risk, contact the fire service on 999 for advice and possible attendance before opening the pile.