Water is also a much better conductor of heat than air, which is why cold water always feels much colder than air at the same temperature. So a wet compost heap loses heat more quickly than a dry one.
In fact, although this is unlikely to happen to you, spontaneous fires at commercial composting sites are not that uncommon, and are usually caused by a large heap that is (at least in part) too dry. The message is that moisture content is critical: it must be high enough to allow composting to occur, but not so high that heat is lost too quickly. On a domestic scale, the moisture content of a compost heap is difficult to measure or control: quite small variations in moisture content are probably responsible for the rather unpredictable behaviour of the typical heap.
Finally, does it work? That is, if you have survived the assault course needed to assemble a compost heap in the required manner, will it do what it should do? The Royal Horticultural Society research described previously (see pages 60-61) plainly shows that it probably won't. The only simple way of ensuring a compost heap gets hot and stays hot is to make it larger than recommended by the books, and certainly larger than a typical compost bin.
It seems clear that classical hot composting was designed by (and for) people with big gardens, plenty of space, and ready access to outside sources of compost materials, typically animal manures. In such gardens, classical composting is still alive and well. At the RHS Garden, Wisley, in the UK, huge quantities of waste are chipped, shredded, and mixed by special machinery, then blended into huge heaps, typically 2x4x12m (6x12x40ft) in size, or about 100 times the minimum recommended size of the domestic heap. This makes excellent compost in about four months, but it's a process the ordinary gardener can only dream about.
Of course, I'm not saying it's impossible to make a traditional, hot compost heap in an average bin. It's just that you will have to take some elaborate precautions, probably including more than one of these steps:
At which point, the average gardener could be forgiven for concluding that the game is hardly worth the candle. Gardening is supposed to be fun, after all.
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