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Composting: What You Might Not Know

By: Dr Gareth Evans - Updated: 5 Oct 2012 | comments*Discuss
 
Composting Energy Community Particle

Gardeners and horticulturalists have been encouraging waste plant material to break down to form nutrient-rich compost for centuries – and using it in pots to grow new plants, or to improve the condition of the soil. While the idea isn’t anything new, over the last couple of decades, more and more people have begun turning to composting as a way to reduce the amount of waste routinely buried in landfill – and cutting back on the transport energy required to collect it and get it there in the first place.

Composting fits in remarkably well as a community project, when everyone joins together to compost the waste centrally, at a single site. Although the basic method isn’t particularly difficult to grasp, the composting process is a study in its own right and while you certainly don’t have to know it all to make good compost, a little understanding can only help – so here’s a few things you might not be aware of, just to get you started.

Particle Size and Shredders

The 'perfect' particle size for composting inevitably represents something of a compromise. The smaller the individual bits of material are, the more of them is available to the bacteria and other micro-organisms which break them down into compost. However, to make good compost, you need good aeration – so if the particles become too small, they’ll tend to get compacted and there won’t be any spaces between them for the air to circulate. On the face of it, it’s a bit of a "heads I win, tails you lose” situation – but with experience you can learn to judge it about right.

While it’s possible for individual gardeners to chop up waste for their own compost, if you’re running a community scheme, it’s not going to be possible to do it all by hand – so sooner or later you’re going to have to think about a shredder – whether you buy, hire or borrow one from your local council. They bring a number of advantages, including:

  • Faster composting – shredded waste tends to compost faster
  • Better compost – the end product tends to be a finer and more uniform material
  • Greater flexibility – woody prunings and other 'difficult' material can often be composted once it’s been shredded
  • Mulch production – take in Christmas trees in January and you can shred them to make a valuable mulch
However, it’s important to remember that shredders come at a cost – and not simply a financial one. They are noisy, use a significant amount of energy, expensive to buy and present a health and safety – and often an insurance – issue for their operators and the project itself. Never-the-less, despite their drawbacks, they are a major boost to any community composting scheme.

Keep it Moist

Moisture is essential to good compost production. Now while this doesn’t come as news to anyone who has ever made his/her own compost, it’s an area where community projects can often go wrong, particularly at first. The problem for even experienced garden compost makers is that while you can intuitively develop a 'feel' for what’s right in your own 300 litre bin, it’s not so easy to do the same thing when you’re dealing with tens of thousands of litres - and more! At this sort of scale, something a little more scientific is called for.

The ideal moisture content for good composting is about 60 per cent, although it’s not too exacting; you can be 10 to 15 per cent out either way and still end up with a perfectly acceptable product. Getting the level right and then maintaining it calls for a bit of vigilance. Some types of garden waste are naturally spot on, but other kinds can be surprisingly dry – perhaps containing only 20 or 30 per cent moisture – and others can be too wet, so it can be a bit of a balancing act to get the mix right.

Of course, the job doesn’t stop there; composting material gradually loses moisture – largely by evaporation – which means whoever is actually responsible for managing the scheme is going to have to do a spot of watering from time to time.

The Benefits of Compost

Many of the benefits of compost are well known, especially in terms of soil conditioning, addition of nitrogen, phosphorus and potassium (N,P,K) to the ground and improved water retention, but there’s one aspect which is much less appreciated – natural disease control. Properly made compost contains a range of naturally occurring fungicides and a whole host of various kinds of essential soil bacteria and other microbes, which improve the soil environment and help control disease.

However, perhaps one of the most intriguing applications of this particular property is the use of 'compost teas' – infusions made from steeping compost in water for several hours or even days – to combat a series of moulds and fungal wilts that commonly afflict a range of plants. As horticulturalists and gardeners across the world have found out, it really does work!

Composting may well be an age-old practice, but there’s no denying that it’s as relevant today as it’s ever been – and a fantastic way for any community to make a useful product and reduce the amount of energy used to transport its rubbish at the same time. Now that’s really taking the ‘waste’ out of waste!

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