When biological matter decomposes, it produces heat, and a great deal of it. When turning a compost heap in winter you will notice that the pile is steaming. This is proof of the high level of heat within the compost. Put this heat to good use by using it to heat a greenhouse. Not only is this natural and therefore beneficial for the environment, it also costs nothing, unlike electric heaters.
Measure your greenhouse to decide on the size of container you need. Very large greenhouses or growing spaces will need boxes or containers at least 1 m by 1 m (40 inches by 40 inches). Small spaces need containers that fit comfortably on the floor beneath the benches where the plants are growing. The ideal containers are wooden crates or boxes as they have wide openings that allow the heat to escape easily.
Fill the containers with organic matter. Vegetable peelings, newspaper, grass cuttings, tree branches and garden waste all make excellent compost. You also can fill the containers from an existing compost heap, which will liberate some additional garden space. Throw in a few handfuls of ready made compost into each container to help get the decomposition process started.
Stamp on the matter in the containers to flatten it. The more densely packed the matter is, the more heat it produces. The containers don't need covering with lids because this will prevent the heat from rising out of the container and heating the plants.
Place the containers in your greenhouse. Place them on the floor beneath the bench tops where the seedlings are growing.
Turn the organic matter over every month to help the decomposition process and ensure the level of heat within the compost remains high.
Locate your containers from salvage yards, car boot sales, friends or the attic. If you are unable to find any suitable containers you should buy wooden boxes from the hardware shop that are the correct size for your greenhouse. Keep adding to your composting bins by saving kitchen waste and garden matter. Ask your neighbours for their grass clippings and other garden waste if they don't want it.
There may well be an unpleasant odour in the greenhouse. This is just part of the process and nothing to worry about.