Everything that has ever lived will rot down eventually but by changing the conditions we can alter the time taken and the quality of the material produced. Probably most of us make our compost by the simple accumulation in a bin of the various wastes and materials as they become available. The greater the variety of ingredients the better the results and soil is usually added as an inoculant and sanitising layer. Commonly there is not a re-mixing of the ingredients once gathered, thus they rot down relatively slowly and coldly, and so the compost produced often contains weed seeds.
If we make a bigger pile the increased bulk of materials tends to heat up more than a small one so killing more seeds and breaking down more quickly. This is because the volume goes up as the cube but the surface area goes up as the square. Adding insulation can increase the heating effect by reducing losses but if it excludes air can then end up being less effective -making a wetter smellier heap. Activators can help the heating effect but need to be mixed in, any manures or highly nitrogenous wastes mixed in will cause more heat. Indeed the mixing itself is one of the best ways of making better compost more quickly especially if combined with chopping up the materials into smaller bits but it is hard work. (Rotary composters have been made to help with the mixing but I've found them difficult to manage. Likewise shredders make the materials more suited for composting but are dangerous, noisy and irksome to use.)
However almost all variations of the usual composting method are operating at the small end of the heating efficiency scale. It is relatively difficult to produce a good quality compost if you make smaller heaps. The bigger the heap the better the result and I now consider anything less than a cubic metre sized bin to be inadequate. Of course it takes a lot of material to fill large bins and a lot of work to turn them but the quality of the compost made is then superb. I improve it even more by drying the heap and then sieving it. This removes the spoil and makes a uniform friable brown compost suitable for sowing or potting.
Unfortunately few gardeners have large enough plots to create sufficient wastes to fill such efficient large bins rapidly. Many get it right and produce excellent compost from smaller bins, especially those who mix it several times. But it is very difficult for those who have even smaller gardens with fewer wastes. For these there are alternative methods, some of which can also be useful to the larger gardener to run in parallel to the standard compost bin.
A better way of composting small amounts is to use an insulated box. A dead refrigerator on it's back or a small dead deep freezer unit. In either case strip out the bits and bobs and seal the holes with mastic. Give the inside and out a couple of coats of black bitumastic paint to stop corrosion. Make sure the lid cannot be accidentally locked down and remove a small strip of seal in case some foolish kid with a death wish chances by. Then use this box to make your compost. If even small amounts of material are mixed up and put in an insulated box like this where the heat produced is well retained then they cook. Be careful not to add too much wet material without dry as well as this composter runs hot and damp. If too much liquid builds up then make a drainage hole and put a catch tray underneath for the liquid feed. Even with all this insulation sometimes the material is accumulated too slowly to compost well. Don't worry, empty it out, mix it up and put it back; it will cook then! Worm bin- Probably the most well known alternative composting method! It's amazing how many people know of these. A worm composter is effectively a dustbin with a perforated false floor, tap and drip tray. It contains red brandling worms which are the sort commonly found if you turn over an object that has been left lying on the grass for a week or two. These small worms are well adapted to chewing up soft decaying wastes and in a well constructed composter produce both a liquid feed and a very rich compost. The liquid is diluted to feed plants and the compost is mixed into potting composts rather than used on it's own. Although excellent when dealing with very small amounts of wastes you really need a bank of worm composters to cope with any quantity. However one can be run in adjunct to a conventional bin to convert selected wastes as the quality of the feed and compost produced are both high. Worms cope best with finely divided fresh materials, but cannot manage vast amounts of grass clippings, though they will deal with these in moderation if mixed with other ingredients. They eat most kitchen and garden wastes but cannot manage much meat, oils, fats or bones. They love well wetted corrugated cardboard but are not good at breaking down much dry or woody waste. Every so often you have to unpack and repack a wormery in order to get at the well worked material near the bottom above the liquid reservoir.
Snails can be used to make a rich compost for enriching potting composts or a liquid feed. As they rasp with minute teeth they can even cope with quite tough materials. I confine any snails found in my garden to a plastic laundry basket which stands in a moat to prevent any babies escaping. Inside this prison drainage pipes and flower pots create cool places to spend the day and at night my snails emerge to eat the wastes which I put in a tray in the top. They also get a saucer of water and a tray of calcified seaweed. Their droppings fall to the bottom where they could be collected but I prefer to allow these to rot in water and then drain this for use as a liquid feed. And do not think the snails won't cope with kitchen wastes as well as garden ones; they eat a surprising range of things. However they do not eat everything so ideally a snail composter is run in parallel with another sort to deal with their rejects.
Wood lice eat many plant parts generally shunned by snails -potato leaves for example. They are especially partial to chewing up woody wastes and although most of us would hardly want to encourage these little critters I do. I have a slater farm in my hen run where any escapees are soon eliminated! On a small scale you can use a moated plastic laundry basket. They need some bits of old wood etc. to live under and they happily convert the tough bits snails and worms reject into a friable powder that accumulates in the bottom. On a large scale a slater farm is superb for breaking down brassica stems and woody materials which are simply piled into a spare compost bin and converted slowly. When this bin is emptied every few years a good rich compost is found at the bottom closely resembling leaf mould.
Pit & trench
One old method of getting rid of wastes was to bury them in a pit, likewise the practice of emptying the chamber pots into trenches later to be covered by rows of vegetables. This is simple and efficient and can be used in the smallest of gardens. A hole is excavated and as the wastes are emptied in each layer is given a coating of soil. Eventually the pit or trench is filled proud and becomes a mound upon which hungry crops are grown. Runner beans, squashes and pumpkins do well the first year, brassicas the second and potatoes the third. When these last are harvested the hole is ready for re-use as by then the materials have incorporated into the soil.
Wastes are sealed in dustbin bags to ferment rather than rot. Because of the danger of attracting vermin food wastes etc. should not be 'bagged'. However this method is good for grass or green hedge clippings producing a flat slab of gloop that can later be applied as a thick mulch near the base of trees. This method produces a vile smell and the composted material can be somewhat unpleasant to handle but is useful for mixing into the bottom of trenches and large planters.
I used to recommend that weeds with pernicious roots such as bindweed or stinging nettles were wilted and desiccated in the sun for a week or two before composting them. Then I discovered the Roman method of killing weed seeds and roots by immersing them for a month or two under water in a barrel. This kills them! As I have long used Comfrey tea and nettle tea I also tried using the weed tea produced as a liquid feed diluted for my plants in pots. (It's nice to get some use out of bindweed!) It seems to work just as well as any other feed. Later the rotted remains and fibrous bits of now dead root and seed are composted in a bin or wormery. Now I have gone further and make a weed and vegetable soup. Dustbins half full of water stand amongst the vegetable plot and all the weeds and so on go into the soup. They rot and smell disgusting, so I keep the lid on. However the liquid produced is decanted off to dilute for liquid feed, not on the vegetables, but for my tomatoes, fruits and ornamentals in pots. Likewise dustbins in the ornamental areas provide a liquid weed feed for the vegetables such as leeks and sweet corn. Goats- I have it on good authority that one or two of these will soon convert unlimited garden materials into excellent compost with no effort on our parts at all -but I think I'll stick to the safer ways.