Cold heaps and Hot heaps :Types and volume

Cold heaps are built or established over a lonnngggg period and classically contain mainly food scraps and a few grass clippings. They mostly just sit about slowly decaying until you go bandicooting round at the base to see how its all going. Cold heaps can be any size and vary from a pile of scraps growing in the corner of your garden to those contained in structures called compost bins.

Bins can be made from wood (preferably not tanalised) or you can buy plastic fabricated ones in a variety of shapes, sizes and colours from most garden centres.

The idea behind the black plastic bins is that the black will absorb the sun's heat and heat up the composting mixture and therefore speed up the process. They are also handy because you can put them right next to where you want to use them. (Some people also like them because they are tidy.) Some people also use black plastic bags for leaf mulch or as a portable composting system as well. Mostly not the people who like to have a tidy compost bin.

Wooden compost bins. Some people will have one. Many will have more. The three bin system enables one compost to be almost ready/mature, one maturing, and one that is being added to.

Hot heaps are heaps that are built in one go and they do the composting job a whole lot faster. The ideal minimum size in a colder climate is 1.5m3 . You may get away with 1.2m3 in a warmer climate. In a smaller heap you will also need extra insulation such as carpet, sacks or hay to cover and/or wrap your compost heap.

A hot heap requires a little more attention than a cold heap. Unlike the cold heap, for the first week to ten days your hot heap likes you to remember that it is there. It needs turning. The magic formula is heat + mixing. The temperatures we are aiming for in a hot heap are 65-68 °C. If it gets too hot your compost will turn to ash. You may have seen this inside a pile-up of grass clippings that has been sitting around for a week or so.

Turning – After 3-4 days the heap may spike at 68°C (especially at its center). We turn and leave for another 6-7 days. It may reach 65 °C. Then we turn again. The temperature may reach 58°C. Then we leave it to mature til full term which may take 3-5 months depending on ambient outdoor temperature.

When you are turning you can adjust things like dryness by adding more water or nitrogen if need be.