Making Compost, the Myths and Realities

There is a lot of talk about the ‘magic’ of composting. It is often seen as some strange process that is difficult to manage with only the experts able to make good compost. Composting is a natural process that happens in spite of human intervention, all living things die and breakdown without any help. This has to be so, otherwise the Earth would be covered with huge piles of dead things! You would not be able to see any trees because they would be covered with piles of dead leaves.

Many myths remain about how to do it and what sort of ‘bin’ to use. Some people have special brews said to be necessary for composting to work. Others have elaborate bins while others just throw garden rubbish in a corner and call it a compost heap! So what about the myths?

There are lots of ways to make compost ranging from putting everything in a big pile and waiting for it to rot to a ritualised process requiring the ‘old knowledge’ and the use of special potions. All these methods work, some take longer and work better than others. If all you want is to recycle your garden waste without too much effort then you can have an open, cold heap in the corner of the garden, even that is much better than throwing away garden waste and it will produce useful compost.

If you want to buy an attractive commercial bin that looks nice in the garden then go ahead, most work very well. If you are not so concerned about aesthetics then you can use four wooden pallets wired together and lined with old cardboard. The top of the pile should be covered with carpet, or something similar, to keep out the rain.

A popular myth is that the sides of a bin should be slatted to provide a good air flow. Compost certainly needs some air to work but not at the expense of cold drafts that cool the bin and dry out the contents. Paying attention to the contents of the bin and turning the pile at regular intervals will provide enough air to keep the process going.

Most gardens have all that is required for a good compost mix, green material such as soft garden waste and brown material which includes straw, hay (dried grass) and twigs. Grass cuttings, mixed with straw or paper is a good starter and will get the whole process going quickly. It is important not to flood the bin with grass cuttings as this will exclude air and give you a soggy stinking mess, mixing three buckets of grass to one of straw should avoid this. As an alternative you can also use a layer of scrumpled newspaper between thin layers of grass.

Size does matter. If you want your compost heap to heat up and work quickly, then the minimum size for a bin is around a metre cube. It is possible to get heat in smaller bins but it requires some care. A good trick in winter months is to wrap bubble warp around the outside of the bin. I have managed to get temperatures about 60 degrees centigrade in some of the smaller commercial bins.

So what about the contents? The quick answer is that you can compost anything that has lived. It is best to avoid meat, fish and bones as they can attract rodents. You might still get rats if you are composting kitchen waste as they are not fussy and will eat vegetables when hungry. Standing the bin on a piece of strong square mesh wire can help keep them out.

The compost process works best when the ratio of green (nitrogen) to brown material (carbon) is about 25:1, too much green material and it can get wet and smelly, too little green and the process will not work very well.

Some books will argue for layers of different materials often with a layer of earth added to start the process. It really is not necessary to add soil and it can really slow things up by compressing the contents. Adding material in layers is a good way of measuring out the greens and browns but heaps work best after a good stirring. My latest has reached 60 degrees centigrade after 3 days and is still warming up. When the temperature begins to fall the heap should be turned to aerate the contents. It should then heat up again. but will not reach such a high temperature as the first cycle. After one turning you can leave it at that and just wait for the completion of the process or turn it again. In Summer hot heaps can be finished in 6-8 weeks.

It is best to make a whole heap in one go. This may not be easy if you have a small garden but you can save material ready to compost in old dustbins. If you really cannot fill the bin in one go then just add material as available but try to make sure you have the correct ratio of materials. It is also important to have the correct amount of moisture in the heap. If it is too wet it will not work and will stink, too dry and it will just sit there doing nothing. The right amount of moisture is best described as being like a wrung out sponge.

It is important to cover the bin with a waterproof lid to keep rain water out. So for a good hot compost heap:

  • Use a bin/heap that keeps the contents warm.
  • Make sure you have the correct ratio of ‘green’ to ‘brown’ material.
  • Ensure adequate moisture.
  • Use a closed bin with a rain proof lid.
  • Turn the heap when it begins to cool, make a whole heap in one go.
  • Do not flood with grass cuttings.
Material C:N Comments
Urine 2:1 Makes a very good activator, dilute 1:2 with water
Pig manure 5:1
Poultry manure 10:1 Use sparingly; a powerful activator, source of phosphates
Comfrey 10:1 Rich in many nutrients, especially potash. Almost no fibre
Grass cuttings 12:1 Mix with straw/scrumpled paper
Kitchen waste 12:1
Farmyard manure 14:1
Seaweed 19:1
Garden waste 20:1 Near perfect balance
Horse manure 25:1
Weeds 30:1 Its best not to use weeds like couch grass etc
Straw 80:1

Finally, have a go, composting is not difficult and does provide a valuable resource from garden and household waste. Good compost is essential for the Organic gardener and is free for the making.

If you want to know more then have a look at:

“All About Compost”, Pauline Pears, HDRA/Search Press, £6.95.

“The Rodale Book of Composting” published by the Rodale Press, Emmaus, Pennsylvania, ISBN 0-87857-991-5

© Colin Shaw, 1999. No part of this document may be reproduced in any form without the written permission of the author.