Given the number of questions about this, I am reposting my guide.
As Kipling didn't say, there are nine and sixty ways of making
compost, and every single one of them is best.
This is best suited to medium or large gardens (500 square yards and up), though it is feasible in smaller ones. You need 5-20 square yards, preferably out of sight and not right next to the house. There is very little smell, but there can be some. And the heaps are not pretty.
Build 2 or 3 square frames 3' high, either with 3' solid sides or 4' mesh ones. You need to be able to remove at least one side. I bought 10 metres of 3' plastic coated link fencing, and rewove it into two loops. I stretch them into a square by hammering 4 poles into the ground, and it is just possible to pull it off the finished heap. For limited space, solid frames with removable fronts are probably better.
It is useful if you can extend the frames to a second story (say 5' high) for very loose material. However, DON'T build them 5-6' high in the first place! In low-rainfall areas, it can be useful to line them with heavy polythene, but you need to leave some way for air to get in.
On poorly draining soil, make a free-draining base out of bricks or whatever. On sand or gravel, don't bother.
Chuck on all your kitchen and garden waste, including eggshells, bones etc., but try not to get solid masses of anything (especially lawn mowings). It is essential that there is some airspace, though the heap should not be loose. When adding loose material (e.g. honeysuckle prunings), it is worth treading it down, but don't do this for softer material or it will compact.
Keep it damp or wet, but not waterlogged, and water it well after adding dry material and if necessary in summer, but don't worry if the outside dries out. Add some nitrogen (e.g. general fertiliser or human urine!) if you have added a lot of pure vegetable matter.
Cabbage stalks, sapwood and soft prunings are fine (up to 1/2" diameter) if cut into short lengths, but avoid heartwood and prunings with very hard thorns (e.g. pyracanthus and most roses) unless shredded first. Resinous prunings (e.g. conifers) don't compost very well, but small quantities are all right.
You can add newspaper if you loosen it first, and even clothing made of natural fibre. Sawdust, hay and straw are fine. Semi-woody material is particularly useful for clay or sand, because in its half-rotted state it holds water and provides drainage. Spent peat/fibre compost from bought plants is fine, but break it up first; you can ignore the small balls that look like snail's eggs, as they are slow-release fertiliser.
Avoid cat and dog litter because of the chance of human disease, but herbivore litter is fine (whether hamster, horse or hippopotamus). Don't worry too much about diseased plant material, but take some care. The only diseases that matter are those with durable, soil borne spores; with most of those, if you have them, your soil is riddled with them anyway.
Don't worry too much about perennial weed roots or weed and plant seeds, but put them towards the centre, where they will start to grow and die. The one exception is ripe, tough seeds of pernicious weeds (e.g. nettle, goosefoot and some grasses) - do not put those on the heap or allow such weeds to seed onto it. There are very few weeds in this category, and their unripe seeds will not survive.
There is a potential problem with some bought manure (including anything where hay is used as a bedding material) and possibly mushroom compost, because it may contain persistent herbicides, such as aminopyralid and clopyralid, intended to kill all broad-leaf weeds on grassland. This also applies to grass-cuttings from lawns treated with lawn weedkillers. If in doubt, keep them separate and check them for this - see Dow's Web page on aminopyralid.
When you have filled up one heap, start another and let the first rot down. It will take from 9 months to 2 years, depending on how much woody material there is and whether you have let it get too dry. If the mixture and conditions were perfect, you would be able to use it without further action after that period, but this is rarely successful. You should plan on turning each heap over at least once a year, to mix it, check on its dampness and possibly aerate it.
When you come to use a heap, put the insufficiently composted material (e.g. heavy bones, particularly intractable prunings, the top and the outside, if using mesh) onto your current heap and use the finished compost. Greater bindweed will grow through the heap, but little else will. I don't have horsetail, which may also do so. Just chuck the soft shoots onto the next heap - they won't regrow.
Especially on sand and clay, do NOT reject compost just because it hasn't completely broken up - once prunings have weakened so that they break with a fork, you can use it.
And you can recover any kitchen utensils that have been thrown away by accident; silver, glass and some plastics will be intact, and stainless steel can USUALLY be rubbed down and reused. Other materials will normally have corroded beyond hope.
When you have the system going, there is no need to turn a heap over just for the exercise - it can be done as part of the process of using it. But getting into the rhythm of this takes some practice.
Woodlice and earwigs are normal inhabitants (and some layers may be grey with the former), but may indicate it is too dry. Worms of all species are a good sign, but attract birds and badgers. If you get rats, call pest controllers or turn the heap over - the disturbance usually sends them elsewhere.
The advantages of this method over the fancy composters are that you can chuck almost everything on, it needs very little attention, and is good at producing high-fibre compost for sand and clay. The disadvantages are that it takes more time and space, and that turning it is hard work (even if only once or twice a year).
A house and 1000 square yard garden will produce about a ton of compost a year by this method.
By Nick Maclaren revised October 2009
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