For the average gardener, the easiest way to cope with most soft waste is to make a “high-fibre” compost heap. The method described here is based on that developed by the Centre for Alternative Technology (CAT) in Wales, in the UK. Green kitchen and garden waste and paper and card are essential ingredients. Any paper or card you add to a high-fibre heap should be crumpled to make irregular, three-dimensional shapes. Egg boxes and toilet-roll tubes are perfect without any pre-treatment. Start with a layer of paper and card to improve the drainage at the base, then just add paper and green waste as it comes along – no need for any distinct “layering”.
The only rules are to make sure that you have approximately equal volumes of paper and green waste, and not to add pure green waste in a layer more than 15cm (6in) deep.
понеделник, 18 януари 2010 г.
петък, 15 януари 2010 г.
Raking them in
The traditional advice on composting tree leaves is clear and unambiguous: don’t bother. Leaves from trees are low in nitrogen and calcium and high in carbon, especially in tough, indigestible stuff like lignin (the main component of wood) and tannins, so they are best kept away from the compost heap. Yet not all tree leaves are the same, and the usual advice is founded on the assumption that gardeners can’t tell them apart. The real story, for gardeners who can tell them apart, is that leaves of some trees are tough and slow to break down. However, other leaves are much richer in nitrogen and calcium and make a useful addition to the compost heap.
Good leaves Ash, cherry, elm, lime (linden or basswood), maple, poplar (cottonwood), willow.
Bad leaves Beech, birch, hornbeam, oak, sweet chestnut.
Good leaves Ash, cherry, elm, lime (linden or basswood), maple, poplar (cottonwood), willow.
Bad leaves Beech, birch, hornbeam, oak, sweet chestnut.
неделя, 10 януари 2010 г.
Compost for realists
Woody waste can cause such trouble that I’m going to start out by assuming you don’t have any. Later, we will see what can be done with woody waste, but first let’s consider what you can do realistically with the soft garden and household waste and lawn mowings.
петък, 8 януари 2010 г.
The trial heaps were
• a standard, slatted, wooden bin bought from a large DIY chain store, with a volume of 0.75 cubic metre (26 cu.ft)
• a typical, local authority plastic bin, of 0.3 cubic metre (11 cu.ft)
• an open heap, also sized about 0.3 cubic metre (11 cu.ft)
All contained the same mix of typical garden waste: large, woody material was chipped and smaller material was shredded. The trial was started in late autumn: although the weather at this time is too cold to be ideal for compost-making, it is one of the few times that many gardeners will have a large quantity of waste material available.
The trial heaps were compared with the main heap at the RHS Garden, Wisley, which is enormous – at least 30 cubic metres (1,060 cu.ft). Despite air temperatures below 10°C (50°F), the temperature of this heap quickly rose to around 70°C (158°F). After two weeks, the heap was turned and the cold air admitted briefly reduced its temperature to below 50°C (122°F). But it was soon back up to over 60°C (140°F) again, and remained above 50°C, with monthly turning, for several months.
No such luck for the trial heaps. None ever achieved more than a few degrees above air temperature, with or without turning. Probably because of its larger size and better insulation, the wooden bin was the best of a bad bunch, and the plastic bin was slightly warmer than the open heap. Crucially however, none got anywhere near a temperature that would kill disease pathogens or weed seeds. So much for the bad news.
• a typical, local authority plastic bin, of 0.3 cubic metre (11 cu.ft)
• an open heap, also sized about 0.3 cubic metre (11 cu.ft)
All contained the same mix of typical garden waste: large, woody material was chipped and smaller material was shredded. The trial was started in late autumn: although the weather at this time is too cold to be ideal for compost-making, it is one of the few times that many gardeners will have a large quantity of waste material available.
The trial heaps were compared with the main heap at the RHS Garden, Wisley, which is enormous – at least 30 cubic metres (1,060 cu.ft). Despite air temperatures below 10°C (50°F), the temperature of this heap quickly rose to around 70°C (158°F). After two weeks, the heap was turned and the cold air admitted briefly reduced its temperature to below 50°C (122°F). But it was soon back up to over 60°C (140°F) again, and remained above 50°C, with monthly turning, for several months.
No such luck for the trial heaps. None ever achieved more than a few degrees above air temperature, with or without turning. Probably because of its larger size and better insulation, the wooden bin was the best of a bad bunch, and the plastic bin was slightly warmer than the open heap. Crucially however, none got anywhere near a temperature that would kill disease pathogens or weed seeds. So much for the bad news.
събота, 5 декември 2009 г.
Classic composting - part 2
Which raises the awkward question: what do you do with compostable material that accumulates meanwhile? Clearly, if traditional composting is to work at all, you must have at least two compost heaps. “Fill your compost bin with at least a cubic metre of waste.” Naturally, this assumes that you have a compost bin that will hold that amount. So how big are commercial compost bins?
Many retailers sell their own version of the classic, wooden “New Zealand” box; a quick check of catalogues and websites shows that the standard box bin varies from 0.3–0.75 cubic metre (11–26 cu.ft).
You can find larger bins, up to 1.3 cubic metres (46 cu.ft), but you have to look quite hard to find them.
Plastic compost bins, of the type often provided free or at a subsidized price by local government, are generally smaller. A leaflet from my local authority lists three bins, ranging from 0.23–0.6 cubic metres (8–21 cu.ft). Fancier options, such as bins disguised as beehives and tumblers, are smaller still. I’m forced to conclude that manufacturers of compost bins do not expect the average gardener to assemble a cubic metre of compost at one go.
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 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:
• importing composting material from outside the garden
• trying to make compost only in summer
• installing effective insulation around your bin
• siting the compost bin in the sunniest, most sheltered spot
• moving to somewhere with warmer summers.
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.
сряда, 2 декември 2009 г.
Classic composting
The traditional advice for constructing a classic compost heap is quite simple. First, collect together a mixture of soft, nitrogenrich waste and tougher, carbon-rich material. Shred any tree and shrub prunings.
Second, start filling your compost bin with layers of different materials, adding a spadeful of compost or soil now and then – the right micro-organisms will colonize your heap eventually anyway, but there’s no harm in giving them a helping hand. Carry on until your heap measures at least one cubic metre (1 cu.yd), or more if possible. If the heap seems dry, water it. Cover it with the bin lid or a piece of old carpet.
Your heap should soon start to get hot. When it starts to cool, turn it and it will heat up again. When it starts to cool again, turn it for a third time, and leave until done. Sounds simple, doesn’t it? Unfortunately, it’s this stately home approach that caused generations of gardeners to abandon the whole idea of making compost. In fact, this
apparently simple advice is
riddled with weasel words
that gloss over real difficulties.
“Turn your heap when it starts to cool down.”
Modern gardeners are busy people, with their compost heap somewhere near the bottom of their list of priorities. Turning a large compost heap is hard work, and doing it twice sounds like adding insult to injury. There’s also the anxiety of whether you’ve got the timing right. Is it cooling down yet? Have I left it too long?
“Collect together at least a cubic metre of waste.”
Pardon?
How often does the owner of a modern, small garden have a cubic metre (cu. yd) of waste at one time? Pause at this point and try to visualize a cubic metre of garden waste (go and get a tape measure if necessary).
“Well then,” goes the advice, “gather the materials over a
period of time.”
OK, but where do you store this stuff while you are waiting to collect enough? An even more interesting question is how you stop the green waste from starting to compost before it goes on the compost heap. Keep it in the fridge maybe?
Something else the books never mention. As described, composting is clearly a batch process, like putting a load in the washing machine. A full load of compost material is assembled and, after a time, finished compost results.
понеделник, 30 ноември 2009 г.
Sorting your stuff
The lists opposite are a reminder of most of the sorts of things that you might want to compost, divided into (1) soft, nitrogen-rich, (2) moderately nitrogen-rich, and (3) tough, carbon-rich material. Bearing in mind the ideal C:N ratio of 30 for composting, a heap made entirely of rich stuff will have too much nitrogen and one entirely of tough stuff will have too little, so always try to mix the two.
Rich stuff (C:N ratio of 5–25) Annual weeds, coffee
grounds, comfrey, feathers, general kitchen waste, hair, lawn
mowings, nettles, old cut flowers, pigeon manure, pond weed,
poultry manure (raw or pelleted), seaweed, pure wool or silk
clothing (shredded), soft, green garden waste, urine.
Middling stuff (C:N ratio of 25–50) Brassica and other
fibrous, green stems, citrus skins, cotton rags, eggshells
(rich in calcium), soiled bedding from hamsters, rabbits,
guinea pigs (not dog or cat litter), spent hop waste, tea bags,
used potting compost, vacuum cleanings (but not if you have
synthetic carpets), waste from distilling, well-rotted cow/
horse/pig/sheep manure, wool shoddy, young hedge clippings
and soft prunings.
Tough stuff (C:N ratio of 50–600) Bracken, cardboard,
corn cobs (crushed), hay or straw, leaves of broad-leaved trees
and shrubs, leaves of conifers, nutshells, paper, sawdust,
tough hedge clippings, waxed paper, wood ash (rich in
potash), wood shavings, woody prunings.