Compost

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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.

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

A lot has been written about making compost, but the issues that matter on an industrial scale are barely relevant to little domestic heaps, so a lot of composting advice can be safely ignored. The aim for most of us is not to design the ultimate industrial sized compost pile, but just to compost the domestic waste we have.


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, due to worm action and liquid runoff. 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 are very slow to decay. Heaps of only high nitrogen 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

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

Leaves

Fallen tree leaves rot much slower than most other things. This its advantageous to process leaves separately. Expect them to take a year or 2.

Sometimes people chuck in the attached twiggy material too, and separate it out once the leaves are rotted. Its quicker.

Methods

Generally, the hotter the pile, the quicker it processes. Big industrial sized piles are designed to heat themselves, but most of us don't have large enough piles for that to happen.


Open pile

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

Turning it once helps the outer stuff that tends to dry out decompose, making it all go quicker.

Composter

These prevent rat access, improve temperature a bit, and the open base permits worm access.

Binbag

In a tiny garden or balcony, material can be bagged and the bags hidden in gaps behind planters etc. You don't get much in one bag, but its a useful amount for such tiny spaces.

Compost in a black bag inside a clear bag is marginally warmer than a binbag alone, and processes a little quicker. But not much.

Spread on ground

A fair amount of compostable material doesn't need to be composted at all. Much plant matter can simply be spread on the soil surface, and will decay into the ground in its own time. Invasive plants and seeding weeds should not be disposed of this way. Weeds are best left to dry out before putting them on soil.

Trench

Burial in trenches 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, such as fish, as burial eliminates smell.

Put the soil back over the buried material, as it rots down it sinks and leaves a hollow otherwise.

Tumblers

The composting of large amounts is often 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's 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.

Heat is also effective. A plastic cover keeps the pile warmer and damper.


Wood piles

Wood doesn't decay in 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. Preservative treated wood should not be included.

Composters

Plastic barrel

Most popular, but small capacity and high price. Ratproof.

Pallet frame

An open frame of 4 pallets. Much larger & cheaper. As its slatted you should not include foods edible to rats.

Compost fence

Mesh netting is cut & tied to make round tubes a foot or 2 in diameter. These are tied together to make a fence. Compostables fill the fence, feeding the garden as well as fencing it.

The author suspects it might be quicker to instead use 3 runs of fencing netting, the 2 outer ones straight and the inner corrugated, tying the outer runs of net into a rigid structure.

Insulated composter

High temps produce rapid compost. Discussion

See Also