Composting

 

What causes decomposition?

Decomposition results from natural bacterial action and is a complex series of steps whereby certain strains of bacteria, by their digestive and excretive processes, break down the material to a point where other strains take over until the material reaches a user friendly and pleasant state.

The time taken to complete this process depends on the prevailing conditions in and around the compost, particularly temperature, moisture levels and the material being composted. Bacteria are naturally present in the soil and in the refuse before it is composted. Most of the important bacteria are anaerobes, that is bacteria which will grow and flourish only when oxygen is excluded from their environment. However, in the early heat producing stage of decomposition, aerobic bacteria which need oxygen have a vital role. 

What conditions aid the process?

Provided the correct materials are used for compost, the main consideration is to protect the heap from extremes of wetness and dryness. Steady conditions of humidity and temperature are important to bacteria to enable them to develop and their first requirement is therefore an enclosure which provides protection from sun, wind and rain.

What can I Compost?

In general anything organic, this means anything that has lived, can be used to make compost and this includes all types of manure, grass cuttings, leaves, tea leaves, peel, cores, vegetable scraps, weeds, the list goes on and on... Best results may be achieved by mixing a variety of materials prior to putting them into the compost bin.

Yes	No
Soft prunings like privet	Meat and fish scraps, raw or cooked
Hay and straw	Coal ash
Weeds	Large amounts of autumn leaves
Pure wool jumpers	Coal ash
Strawy farmyard and horse manure	Nappies
Old plants and flowers	Dog and cat mess and litter
Bedding form vegetarian pets, like rabbits, guinea pigs and gerbils	Metal or glass containers
Woody prunings, if shredded small
Small amounts of autumn leaves
Grass mowings, although too much can make a smelly heap
Kitchen waste, tea bags, fruit and vegetable peelings and cores, egg shells and so on
Potato tops and other stuff from the vegetable patch

How do you make compost?

Two sets of instructions for compost making are given below, namely the simple and the quicker methods. Both produce excellent results. The main difference is that, as the name implies, the quicker method produces compost faster although it involves a little extra effort.

The simple method

1. Securely position your compost bin on level soil where no flooding occurs and lightly cover the base flange with soil to secure against strong winds whilst empty.
2. Progressively fill the bin with all forms of soft organic refuse - grass clippings, spent plants, leaves, weeds and kitchen waste. As far as possible, try to mix the various materials. Cutting up or shredding woody or fibrous material will help the process.
3. Grass cuttings will rapidly settle between mowings and the bin will contain much more than its volume of cuttings. Simply push the cuttings evenly around the sides.
4. Before depositing the contents of your sink tidy, make a depression in the heap so that such things as egg shells and orange peel don't slip down the outside of the heap.
5. When you have a good 'solid' heap either leave it and start another bin, or lift the bin off the heap and move it to a suitable part of the garden, ready to start again.
6. If you have removed the bin to start again then cover the exposed heap with a sheet of black polythene, weighted around the edges.
7. Allow about three to five months for the heap to mature (the process can be faster in hot weather). Worms and microbes will now complete the job.
8. You should now have an excellent quality, nutritious compost ready for a variety of horticultural uses. The benefits to plant growth and soil structure are quite simply remarkable.

Compost activators and additives

A compost activator can be anything that is rich in nitrogen. If you wish to use an activator, some farmyard manure or if you wish human urine work excellently and are certainly cheaper than proprietary brand activators. A natural way to combat acidity is to add calcified seaweed which will also add valuable trace elements. But activators and additives are by no means necessary.

The quicker method

The already impressive speed of action of the compost bin can be further improved if you are prepared to put in a little extra work as follows:-

1. Collect your waste material and keep it in a polythene sack until there is sufficient to fill the bin.
2. Place a layer of newspaper on the soil at the base of the bin (this not only helps to recycle newspapers but also prevents too much soil being lifted when the contents are turned).
3. Fill the compost bin with the waste material. Try to mix various waste products rather than having thick layers of one material. Alternatively, if you have large quantities of grass cuttings place a layer of screwed-up newspaper between every 3 inch layer of grass to help trap air in the cuttings. Don't compact the contents as this will reduce the air content. Securely replace the lid.
4. Leave the bin undisturbed for 7 days. Heat generation can exceed 60°C during this phase. This high temperature kills weed seeds and disease, making the compost sterile. As the water content reduces, the level will drop. Don't be tempted to top up the bin with fresh material at this stage as this will slow it down.
5. After 7 days lift the bin off the compost and place it to the side. Using a fork, turn the heap back into the empty bin. This time do not line the base of the bin with newspaper.
   Replace the lid and leave undisturbed for a further 7 days. The bin will reheat to high temperatures thus reinforcing the first sterilisation stage. Further turning of the heap is neither necessary or desirable.
6. The bin should now be left for a few weeks (typically 6-8) for naturally occurring worms and microbes to digest the compost into an excellent quality soil conditioner, plant food and all round 'superior' compost. It is not possible to give exact timings - but by occasionally testing the compost (ie, how it looks and feels) you should know when it's ready for use.

In what circumstances should compost be used?

Compost is excellent for virtually all soil types. It improves water retention in light soils and drainage in heavy or clayey soils. As well as improving soil structure it adds valuable plant nutrients.

Dig it in

Typically an autumn job but can be done throughout the year.

How do I make a potting compost?

Mix 3 parts of compost with 7 parts of loam soil and 3 parts of horticultural grade sand for a good general purpose potting compost.

 

Mulching

Simply spread a 3 to 4 inch layer over the soil surface and around your shrubs and plants. This helps suppress weed growth and helps water retention.

 

Troubleshooting

Making top quality home compost is usually a simple and easy matter,
but here are a few tips if things don't seem to be going as expected.

Symptom	Cause	Remedy
The compost is too dry	Too little green waste added and dry material not dampened	Moisten and turn the compost
Compost is cold even in centre	Simply not enough waste or wrong mix	Add more material especially green waste such as grass clippings
Flies	Kitchen waste not buried or the use of inappropriate material such as fish or meat	Bury the kitchen waste and check the tips on what to compost
Odour	Compost is too wet and compacted. Too much green waste, e.g. grass clippings	Turn the compost and mix in twiggy fibrous material such as straw

Hot tips for composters

• Set the bin on bare soil for drainage.
• Add a mixture of tough and tender stuff.
• The more you put in at once, the quicker it composts.
• If lots of stuff is added together, it will probably heat up and can get to 60°C.
• Don't worry if it's not hot.
• Compost activators, "Hot Stuff' get the composting started.
• If you are not using a compost bin, cover the heap to keep the rain out.
• A soggy, smelly heap needs more tough dry stuff.
• A dry heap needs watering.
• Fine and crumbly, lumpy and stringy, all compost can be used.
• Chop up tough stems or smash them with a spade to speed up. A shredder is a great help.
• For a quicker return, turn the heap now and again. Empty the composting bin, mix everything together, adding water, an activator or something dry if necessary, then put it all back.
• Compost is good for all soils. It makes heavy soil easier to work and helps light soil hold water. It feeds the plants too.
• Use compost in the spring and summer. Spread on the surface or dig in to the top few inches of soil.
• Composting is quicker in summer.
• Stuff wet autumn leaves into bin liners or a wire cage. Use them on the garden a year or two later.

These 'Hot tips' are reprinted with the kind permission of the Henry Doubleday Research Association