Usually fixable

Why is my compost not heating up?

Usually because the pile is too small, too dry, or short of nitrogen, in that order of likelihood. Also worth saying plainly: a cold pile is not a broken pile. It composts anyway, just slower. Below: what causes compost not heating up, how to fix it today, and how to stop it happening again.

A compost thermometer reading low in a cold pale compost pile, compost not heating up — Compost not heating up.

Check size first

Below roughly a cubic metre, a pile physically cannot retain the heat it generates. This is the single most common reason and no amount of turning or additives will fix it. Build bigger, or accept cold composting.

Then moisture

Squeeze a handful from the middle. Dry and crumbly means the microbes are dormant. Water as you turn, layer by layer. Water poured on top of a dry pile runs off and down the sides.

Then nitrogen

A pile of leaves and cardboard alone has almost nothing for microbes to build with. Add greens: grass clippings, food scraps, coffee grounds, manure.

Then air

A compacted pile has no oxygen in the middle. Turn it and it will often heat within a day.

When cold is simply correct: in winter, or in a finished pile that has already been hot and used up its easy food. A pile that heated and then cooled has not failed. It has moved on to the slow stage.

The underlying biology: how composting works. Symptom index: compost problems.

Why is my compost not heating up?

Check size first

Then moisture

Then nitrogen

Then air

Related

Further reading on compost not heating up