Why Does Compost Get Hot?

Microbial Action Breaks Down Organic Material

Compost is created by the breakdown of a 50-50 mix of organic materials that are dry and brown and moist and green. The decaying organic materials are layered or stacked in large pens or containers that allow for some air circulation. Oxygen mixes with the organic materials and water to create ideal conditions for decay, inviting bacteria and other microorganisms to the compost pile.

Heat Byproduct of Bacteria at Work

Bacteria feast on the rotting organic materials; one byproduct of their consumption is heat. When larger compost piles are assembled, the interior heats up because the waste and heat byproduct is insulated by the surrounding material and cannot escape. When a compost pile cools, that means that the breakdown of materials is complete and bacterial activity has slowed considerably.

Increase the Heat & Speed the Process

The composting process can be sped up by introducing additional elements that boost bacterial breakdown and therefore increase the heat production. Turning and flipping the compost pile every few weeks feeds oxygen into the process. Worms and nitrogen-rich fertilizer can be added to support the breakdown process and increase the resulting richness of the compost.