If your garden is large enough to produce garden waste then it's large enough to have a compost heap tucked away somewhere. This will enable you to convert all your garden waste into valuable compost which in turn will help to produce a more productive soil for your plants to grow in.

• Composting is easy.
• Composting produces a very cheap soil improver - much cheaper than buying bags of it from the local DIY store!
• To maintain a healthy soil and thereby healthy plants, the soil needs to have organic carbon replaced.

A large proportion of the household waste that is collected by Medway Council is garden waste. The European Landfill Directive will soon ban the landfilling of this waste as it causes the production of methane from landfills which is a very potent Greenhouse Gas. It can also pollute ground waters which we end up drinking from our taps.

The application of home compost will improve your soil's structure and feed the micro-organisms that ultimately feed your plants. Left to its own devices nature would replace this organic carbon when plants die and decay but most gardeners tidy up the dead plants and remove this valuable carbon.

During the composting process the micro-organisms consume oxygen and nitrogen and produce carbon dioxide. If this takes place in the soil then the growing plants would be deprived of nitrogen. Therefore it makes sense to collect up all the plant material and compost it in a controlled manner in a compost heap. Once completed, and the compost is mature, it can then be safely added back to the soil.

A good mature compost helps to improve the soil structure, feeds the micro-organisms in the root-zone and adds around 1% nitrogen, 1% phosphorous and 1% potassium back to the soil to feed the growing plants. In addition to these macro-nutrients it also adds many valuable micro-nutrients such as copper and zinc that are not found in chemical fertilisers.

The Medway Council can offer a range of plastic compost containers that hold sufficient for a small garden, made of a green recycled plastic, which helps them to blend into the garden. In my opinion the best of these is the round one which has a rim at the base that turns outwards. This allows the container to be removed from the heap more easily than the designs that have a base rim that turns inwards. This is important as all compost heaps should be turned from time to time to allow air into them. If your heap does not get sufficient air it will stop composting and start anaerobically rotting. This is when ammonia and methane are produced and the heap stinks!

The heap

There is nothing magical or mysterious about a compost heap. It can be as simple as a pile of material in the corner of a garden or as complex as an electrically heated, automatically turned, stainless steel gizmo. If the heaps are kept aerated, the only real difference is the speed at which the compost matures into a good stable product. This can range from 14 days for the state-of-the-art gizmo to 6 months for a good old fashioned heap in the corner.

Aeration

The real secret to making good compost is to make sure that the heap has a good supply of air so that it does not go anaerobic. If this happens a different group of bacteria start working on the heap and producing ammonia & methane which is when the heap starts to smell and annoy the neighbours. To prevent this happening requires the heap to be turned once in a while and for it to contain some coarser structure material like small twigs, corrugated cardboard, woody plant stems etc.

To help aerate a simple heap, and to make it look tidier, you can simply hammer four 1.5m long stakes into the ground to make a 1mx1m square and then attach chicken mesh around three sides of the square, Leave the fourth side open to allow access.

What can go into the heap?

Almost anything that has once lived can go into a compost heap but to ensure that you don't attract rats and other vermin it is best not to put meat into the heap unless it is in a secure (metal) container. The secret here is that you want around 30 parts of carbon to every part of nitrogen and about 50% moisture content. Don't worry, that's for ideal composting conditions and if you mix up what you put on the heap the result will be somewhere close to the ideal.

So to ensure the correct mixture, good aeration and moisture content don't put too much of any particular material onto the heap at the same time. For instance, do not mow all your lawns and put the grass clippings on all at the same time - these are high in nitrogen and low in carbon and quickly compact down to form a soggy mess. Therefore put these types of materials on in layers with some other materials like weeds, corrugated cardboard, kitchen peelings etc. in between.

Weeds in a compost heap?

It is possible to add weeds to a compost heap and not end up spreading them all around the garden. However, to do this it is necessary to ensure that the composting process kills the roots and also any seeds that are present. This will require the heap to heat up to over 60C for a reasonable period of time.

There are many types of compost heaps which work at different temperatures, so called cold composting and hot composting. The composting process releases a large amount of heat which enables the heap to heat up to quite high temperatures if it is well insulated. Very large piles of compost have been known to actually catch fire. This self-heating happens naturally in large heaps of many cubic metres but is harder to achieve in small heaps unless properly constructed.

Most plastic containers are cold composters, they do not hold much material, have a comparatively large surface area and have quite thin walls. Therefore the heat that is generated escapes very easily and does not raise the temperature sufficiently high to kill weeds. It is not recommended to add weeds to these types of heaps. In addition the lower operating temperatures makes the composting process take longer. At normal outdoor temperatures the process will speed up by a factor of approximately two for every 10C increase in temperature.

However, it is possible to construct relatively small compost heaps that operate at higher temperatures in your garden. The one shown on the left was made out of old pallets with scrap expanded polystyrene pushed down in between the top and bottom surfaces of the pallet. Obviously more pallets were used to supply wood to fill in the gaps between the slats of the pallets. Pressure treated feather-edge boarding was then used on the outside to give a good looking finish. The heap has a removable front section (shown removed) to allow for easy turning of the heap from on side to the other. A hinged lid was then added (shown raised) to keep the rain off and the heat in. A piece of old synthetic carpet can be used on the top of the material to keep even more heat in for winter composting.