Our Sustainable World: Composting

Posted by Marc at 12:08 pm on 03 December 2009

Small Recycle Symbol Making compost is a very simple process. If you throw the stuff in the dustbin it will be wasted and end up in an expensive and undesirable landfill site, where it will do no good at all. The result of composting is a free supply of the best possible soil improvement material for your garden and an alternative to all the expensive artificial fertilisers and peat.

Nah, not really. It's all based on natural processes that ensure most living things that die rot away (or decompose). The world is full of organisms that feed on dead material, breaking it down to products at the foot of the food-chain - they are Nature's Recyclers. Wherever you find dead things you'll find a concentration of them doing their job. In composting we simply utilise their natural abilities to turn waste vegetable matter into a nutrient rich humus which you can add to your garden soil to boost it's growing power, improve it's structure and moisture content.

Composting cartoonYou don't need any fancy equipment to begin a compost heap. Start in an out-of the-way spot in your garden on bare soil, not on paving or concrete, and simply start to build a heap from all of your waste vegetable material. It's best to start off with a course layer of prunings, bark and twigs to allow air to enter the heap more easily (more of that later). You can knock together a rudimentary three-sided frame out of old pallet wood to hold the heap in place and help it's efficiency (Click here for instructions); or you can make your heap in an old plastic dustbin with the bottom cut off.

Once the heap has reached a reasonable size, those tiny organisms will really get to work. In fact they work so hard that the temperature in the middle of your heap can reach 70ºC within two or three weeks (although it is more usual to find temperatures of around 50ºC). It will take four to eighteen months (depending on conditions) before your heap is ready to add to your garden soil. You'll know when it's ready when it's dark in colour and has a sweet earthy smell. Of course, the recently added material at the top of the heap won't be ready yet, so simply use the stuff from the bottom of the heap and put the rest back to continue.

  - Fruit and vegetable peelings
  - Prunings and broken-up twigs
  - Grass cuttings*
  - Cut flowers
  - Autumnal leaf falls
  - Horse, rabbit, pigeons & chicken manures
  - Straw
  - Feathers, hair and fur
  - Tea leaves/bags and coffee grounds
  - Shredded wood/branches
  - Crushed egg shells
  - Shredded newspaper
- Meat, meat products, fish or cheese
- Cooked scraps or scrapings
- Persistent weeds** or weeds in seed
- Diseased plants
- Soot or coal ash
- Human faeces or used nappies
- Pet litter or pet waste
- Metal, glass, plastic, artificial textiles
* In layers not exceeding 10 cm. ** Especially bindweed.

The micro-organisms and bacteria that turn your heap into compost require three things: vegetable matter, moisture and air. Excluding air means that you'll encourage "anaerobic" organisms to get to work and turn your heap into a smelly, slimy mess. So one essential bit of heap maintenance is "turning". This means turning the heap over with a garden fork once every fortnight to mix and aerate it.

Your compost heap needs to be kept moist, but not wet, so keep it covered to keep out the rain and water it a little if it becomes too dry.

Heat is essential for rapid maturing of the heap. The heat is self-generated by the organisms as they break down the vegetable material, but the heat may be easily lost in cold weather. You can help by covering the heap with old carpets as the days get colder.

Things that will help accelerate the composting process are nettles (especially young ones, but avoid putting the roots in), chicken manure and human urine.




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