Compost

Composting may be used to dispose of some DIY wastes as well as general garden material. Its also used to turn barren subsoil into fertile topsoil, useful after building projects.

A lot has been written about making compost, and quite a bit of it can be safely ignored. The aim for most of us is not to design the ultimate industrial sized compost pile, but rather to compost whatever domestic waste we have. Composting is one of those subjects where the issues that matter on an industrial scale are barely relevant to small heaps.

Composting is simply the decay of a range of materials to form humus.

Purpose

Composting gets rid of waste by reducing it to a fraction of its size, and converting it to humus, the plant feeding element of topsoil.

Composting can be used to bring low fertility ground back to health. For this purpose, it works better if material is composted in situ rather than elsewhere. This is an excellant way to turn infertile subsoil into topsoil, a frequent problem with new builds, and less often garden remodelling. Artifical fertiliser does not fully replace the humus element in topsoil, and plant growth is likely to fail until humus is introduced.

Composting also gets rid of a couple of types of DIY waste.

Contents

Any of the following are fine:

• Non-woody plant material
• Uncooked plant based foods
• plain paper, card, cardboard
• paper, card & cardboard with black print
• egg shells
• Soiled animal bedding
• animal dung & urine
• cat litter, used
• plasterboard, broken up
• sawdust in moderate amounts
• Cooked foods can be used where smell is acceptable
• Wood ash (not coal ash)
• cigarette ash
• fruit juice
• the soil/compost content of plant pots can also be included

Nitrogen

Compost making is much quicker if the pile contains both high and low nitrogen components. Heaps made of only low nitrogen material will be very slow to decay. Heaps of only high nitrogen will smell bad during decay, and often go slimey.

High nitrogen

• Non-woody plant material
• Uncooked vegetable foods
• Soiled animal bedding
• animal dung & urine
• Cooked foods
• fruit juice

Low nitrogen

• plain paper, card, cardboard
• egg shells
• plasterboard, broken up
• sawdust in moderate amounts
• the soil/compost content of plant pots
• Wood ash

Methods

Generally, the hotter the pile, the quicker it processes. Big industrial sized piles are designed to heat themselves, but 99% of us don't have large enough piles for that to happen, so other warming methods are sometimes used.

Open pile

Domestic sized piles decay slowly. Contact with the ground enables worm access, which improves speed some.

Bin

A black bin will compost a bit quicker, since it warms in the sun and provides just a little insulation from cold air. A bin with a big hole in the bottom to let worms in is best.

Bag

Black bin bags heat up in the sun, speeding things up a bit. But you don't get much in one bag.

Bag in bag

Compost in a black bag, which is then put inside a clear bag and left in the sun will get very hot. The bacteria and fungi that survive this can then work very rapidly to produce quick compost. Again only for small amounts.

Spread on ground

A fair amount of compostable material doesn't need to be composted at all. Plant matter can simply be spread on the soil surface, and will decay into the ground in its own time.

In principle other materials can also be used this way, but appearance usually prevents that. Including weeds is not recommended though, and raw dung on the garden is rarely appreciated by plant or human.

Surface spreading is only a good idea when the compost contains only known plants that won't take root and spread, and doesn't contain weeds. And its not suited to kitchen scraps etc.

If animals eat the compost material, they will also deposit manure.

Trench

Burial in trenches is sometimes used. It gets rid of largish amounts immediately, but is only practical when a digging machine is on site or ground is being filled. A covered trench can accept a wider range of material, as smell is eliminated.

Tumblers

The composting of large amounts is sometimes sped up by repeatedly moving the cold outer material to the hot middle. However domestic sized piles don't usually generate a hot centre, making tumbling not so worthwhile.

Cold frame

A compost mix rich in manure is sometimes put in a cold frame, with a layer of peat or similar on top. Composting generates heat as well as plant food, and plants such as squashes may be sown a month earlier in the frame. Squashes love heat and lots of rotted turd.

Turning

Turning the pile part way through speeds up the processing of large open piles, where there is a significant temperature difference between interior and exterior.

Activators

Activators are useful to dispose of piles that are low in nitrogen, and would otherwise take a long time to rot.

Compost activators are normally sources of nitrogen. Animal dung & urine are full of nitrogen, and are the classic DIY activators.

Heat is very effective, more so on domestic piles than nitrogen activators.

Wood piles

Wood can't be put into compost heaps. Wood piles decay over years to produce compost eventually, and during their existence they provide good homes for pest eating insects. Hence some organic gardeners pile twigs and small branches rather than shredding them. Climbing and trailing plants can grow over the pile. Ideally wood from DIY that's been preservative treated is not included, but many insects will still live in it.

See Also

• Wiki Contents
• Wiki Subject Categories