Composting is the process of purposely turning organic waste into humus and soil, for the purpose of enriching existing soil. Compostable materials consist of biodegradable materials, which are broken down into CO2, water, and biomass by the action of micro-organisms, and compostable materials, which are consumed by micro-organisms, worms, and other living things, and turned into humus. The end product of composting is a rich organic material that can be added to condition and fertilize the soil.
Composting dates back to the days of Rome, and was practiced by piling up organic materials and letting them sit for a year, until the net planting season. It was modernized in the 1920s and succeeding years by scientific experimentation, although in practice the process by which compost is made has not changed.
How composting works:
In ideal situations, materials that contain a large amount of carbon (wood, paper, straw, grass clippings, dead leaves) are added to materials that contain large amounts of nitrogen (kitchen waste such as vegetable and fruit peelings, used coffee and tea grounds, juicing residue, manure, hair, and other materials (discussed later) at a ratio by weight or volume of 30 carbon materials to 1 nitrogen material. In common situations, carbon materials tend by their nature to be brown, and so are often referred to as "brown matter", whereas kitchen waste tends to be green, and is referred to as "green matter." The bacteria present everywhere consume the materials and their residue becomes fertile biomass.
Types of composting:
- Active (hot): Hot composting may be used for the composting of materials (manure, meat, eggs, dairy, grease, cooking oil and manure of omnivores or carnivores) not recommended for other types of composting. This involves a procedure of maintaining a compost pile at a temperature exceeding 55 °C (131 °F) for several weeks. This partially sterilizes the matter and kills stray weed seeds, many bacteria, and insects and their larvae. However, the average home composter cannot rely on this method to kill pathogens; strains of E. coli have been shown to survive high temperatures for over four months. This method is mostly used in industrial composting, although this can be achieved at home. There should be an adequate mix of high carbon-materials to high-nitrogen materials, about 50% humidity, and the compost should be turned every six to ten days. A pile for this method should be about 1 cubic metre and will take approximately four months to mature.
- Passive: Passive composting is what most individuals practice. With this method, kitchen scraps are put either in a bin, or in a pile outdoors, and mixed with high-carbon materials. Unless sufficiently maintained, this pile can get quite evil-smelling, and so it is best to have a large supply of dried high-carbon material available to keep the humidity at a low level. This pile may be largely untended, or tended with turning every few days. Although this process is much slower, it is far less labour-intensive and more accessible to both the beginning composter and the average individual composter.
Half-finished passive compost
- Worm composting: By making a bed of moist shredded paper, someone who lives in an apartment or in a cold climate can compost by adding Red Wriggler worms, and feeding them with kitchen waste (fruit and vegetable peelings, used coffee and tea grounds). The worms will eat the kitchen waste and leave worm castings, which are high in nutrients and beneficial microbes.
Benefits of composting:
- Composting keeps waste out of landfills. Kitchen waste, in particular, in landfills, emits more greenhouse gases, particularly methane. Home composting does not emit methane and produces far less greenhouse gas.
- Composting provides rich matter to fertilize and condition the soil, reducing the need for added fertilizers, especially those made by industrial processes, whose usefulness has come into question.
- Composting can also soften plant material, making the nutrients in the plant more accessible, and can convert the ammonia in the plant into proteins.
- Composting reduces an individual's carbon footprint, because no energy is required to transport matter to another area.
- Rich soil leads to healthy plants, healthy plants deter pests, and so the need for pesticide use is reduced.
Different methods of home composting:
- Bin method: Composting in a bin simply requires a small plastic, wood, or metal bin. Materials are added to the bin and allowed to decay. When the ideal ratio of high-carbon and high-nitrogen materials are added, there is little or no odor. Some of these bins are tumblers; some individuals with small ones simply shake theirs from time to time. Eventually the material inside converts to a soil-like consistency; at this point it can be spread in the garden.
A compost bin
- Trench method: A trench is dug and filled with kitchen waste, covered with dry, high-carbon materials, and filled in with the original topsoil Planting can occur in this area after a minimum of one month; ideally a longer period will allow for more thorough breakdown of materials.
- Sheet method: In this method, kitchen waste, alternating or mixed with high-carbon materials, is spread evenly and thinly over an area. For individuals who generate little waste, this method might be ideal. New layers are spread over the top of old layers; as rain, watering, and soil compaction occurs, the older layers are pushed into the existing soil. This may also lead to higher nitrogen levels in the soil and the slower release of minerals, both desirable for plant cultivation.
- Bokashi method: Kitchen waste is inoculated with beneficial microbes and placed into a tightly-sealed container. After two weeks the container is opened and the contents buried in the garden. Care must be taken not to plant too close to sensitive plants or bedding plants like lettuce.
How to use compost:
Compost may be added to the top of the soil as a mulch, or turned into the soil to improve soil conditioning. It may also be steeped in water, and the water used to water the plants (known as "compost tea"). It is best to let it age and not to plant plants like lettuce too close to freshly-composted areas, but rather to wait a year to allow adequate absorption time into the soil. Other crops which are not as sensitive, are able to be planted in freshly-composted areas.
It is not necessary to start all at once. Perhaps the best way to begin composting is simply to open your used tea bags and shake the contents into the garden, or spread your spent coffee grounds there. Once you are in the habit of doing this, you will find that the next steps come quite easily.
All in all, composting provides numerous benefits, and is easy to practice. So before you throw out those vegetable peelings, or your children's uneaten veggie snacks, or you throw away those coffee grounds or tea bags, ask yourself: Should I compost?
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