Compost is one of the most energy efficient and green ways of improving the quality of the soil on a permaculture plot. It avoids wastage by transforming refuse from the garden and the kitchen into nutrient-rich humus that when added to soil will provide the plants growing in it a plentiful supply of the nutrients they need to grow, thrive and set abundant crops.
There are two fundamental forms of composting technique: hot and cold. The former is quicker at turning organic material into usable compost, but does require more time and effort from the permaculture gardener to achieve the effect. Hot composting involves keeping the temperature at the center of the compost pile elevated, ideally to somewhere between 110 and 140 degrees Fahrenheit. The pile needs to be kept moist – so that it is the consistency of a damp sponge – and the gardener needs to turn it once a week or so. This moves colder material from the outside of the pile to the inside where it is heated and so breaks down into rich humus more quickly. Hot composting has the advantage that it will produce useable compost quickly, and the high temperatures mean that it can break down weed seeds. The permaculture gardener should avoid adding such seeds to cold composting methods, as the more passive form of transformation does not reach the temperatures required to break them down. Cold composting essentially means creating a compost pile and leaving nature to do its job. It requires less input from the gardener, but does mean that useable compost can take up to a year to be ready.
The ingredients for both hot and cold composting are the same, with roughly equal parts brown and green material. The brown material consists of items such as branch prunings, leaves and twigs, while the green portion comprises things like fruit and vegetable scraps and grass clippings. To this can be added livestock manure (although do not use cat or dog waste, as these can contain pathogens that are harmful to humans), and soil (which will contain bacteria and microorganisms that will start to break down the material), along with such miscellaneous items as coffee grounds, shredded newspaper and eggshells. However, while the ingredients are similar, within the two categories of hot and cold composting there are several different methods you can use to create compost for your permaculture plot.
Referred to in industrial agriculture as ‘in-vessel composting’ composting in a bin essentially refers to any method that utilizes a closed container. It is an easy technique and is adaptable to many different types of permaculture plot, being suitable for gardens, courtyards and even balconies. The contained nature of the bin means that you can compost all year round, but while turning isn’t required, the lack of aeration does mean that the composting process can take upwards of six months, depending on factors such as material used and local climatic conditions. You can purchase a general all-purpose bin or recycle any large enclosed container, such as a barrel.
To quicken the process of bin composting, you can fabricate or purchase a container that can be turned. A crank and pivot means that the whole container can be rotated, shifting the contents so that they are aerated, and thus quickening the decomposition process. However, they are unlikely to reach the high temperatures required for hot composting, so this is a cold technique, although, depending on the materials, a turning bin can produce useable compost within two months.
A pile is simply that: a mound of compost that is open to the air. Some gardeners use recycled bricks or lumber to build a containing wall around three sides of the pile, while other will construct a cage from chicken wire to stop the compost pile spreading too much. Ideally a pile will be wider than it is high, as this helps it retain heat better, but a pile can be used in whatever space is available; it will just take a bit longer for the compost to be ready. (If possible have two piles so that when one has reached a manageable size it can be left to its own devices while new material can be added to the second pile.) The length of time for decomposition will also depend upon whether you choose to turn a pile or not. It is optional, and therefore pile composting can be used for either hot or cold composting.
Sheet composting is very similar to mulching, in that a layer of organic material is spread over the garden bed and allowed to decompose in situ. While mulching tends to use a layer of a single material, such as straw or wood chips, sheet composting involves using different types of material, such as leaves, debris from the garden, kitchen scraps and grass clippings. In conventional gardens, the compost is usually dug or tilled into the topsoil, but as a permaculture gardener wishes to minimize digging the soil, you may want to spread the compost on the ground then add a layer of mulch such as straw over the top. This will increase the rate of decomposition and prevent the compost from being eroded away by rain and wind.
A step on from sheet composting is the pit or trench method. This is primarily used for composting fruit and vegetable scraps from the kitchen. It involves digging shallow holes or trenches into which the scraps are placed and then recovered with the soil. The anaerobic organisms within the soil then break down the material over six to twelve months. IA cold composting technique, it has the benefit of keeping the compost out of sight and is a useful method for when you are establishing new garden beds, as it gives the plants a consistent supply of nutrients in the root area. However, it does require the labor of digging the holes and is not suitable for brown material such as twigs as these would take too long to break down to give the plants any benefit.