Composting
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| This article is part of the Food theme. Alimentation |
Compost is rich in humus and in dietary minerals much like potting soil , it's often used in the garden. It is the result of composting : i.e.letting biodegradable organic wastes decay (mostly vegetal wastes). It can be produced in the garden or in compost centres.
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[edit] The basic principle
Composting is a means to accelerate the natural process of decomposition of organic matter into minerals and humus. It requires aeration since aerobic bacteria are at work during the decaying phase and the temperature can then soar up to 150°F!
After the heating phase, there's a new step during which other processes are at work involving fungi, collembola, worms, nematodes, mites and ciliates that help the decomposition of solid particules.
Composting allows the decomposition of complex organic matter, the degraded and simplified elements can then get back to the natural cycle of organic matter and so be used for plants. It is an aerobic process (requiring aeration).
It's also possible to degrade matter by having recourse to another process that is anaerobic and is called methanogenesis or biomethanation, this process involves the action of archaea. It requires less space than the aerobic process but doesn't produce the same "simple elements". Compost brings humified matter to the soil and so nitrogen and other elements (it's manure), whereas biomethanation releases methane and H2S, i.e. biogas besides.
[edit] Types
Compost varies according to its ingredients and method of production.
[edit] Vegetal compost
This sort of compost is composed of vegetal wastes only (no animal wastes). It can be made at home or in community composters.
[edit] Dry toilet compost
This compost is produced by the wastes of dry toilets (also called compost toilet) and organic matter with a high rate of nitrogen (e.g. straw). It requires expertise to use this sort of compost in the garden.
[edit] Compost from community composters
Large quantities can be produced thanks to community bins or composting centres. It can either be made of purely vegetal wastes or with the addition of algae and manure in the case of co-compost. As it is ripe, it can be used in the garden, it's got a high rate of lignin (from wood) thanks to which the soil will be light and aerated. It can be bought by the pound or in bags.
[edit] Homemade compost
This is the compost anyone can make in the garden (or even on a balcony). The main advantage is it costs nothing.
[edit] Vermicompost
Vermicompost consists in using worms for composting. Worms from manure or other rich organic matter will highly accelerate the process. This means composting is possible in cities, even inside the kitchen. Vermicomposting requires a relatively small composter, it is of very high quality because earthworms will create clay-humus complexes.
[edit] What is compostable ?
[edit] Organic matter for composting (compostable materials)
- Cereals
- Fruits and vegetables
- Peelings
- Dry grass
- Coffee dregs
- Coffee filters that haven't been whitened
- tea bags
- Residues of dried clothes
- Plants of the garden
- Sweeping scraps
- Dead leaves, withered flowers
- Cold ashes (not too much)
- Hay
- Straw
- Weeds (care should be taken to maintain a high composting temperature.)
- Hulls
- Wood sawdust (not too much)
- Tissues, kitchen paper
- Newspaper (depending on the ink)
[edit] Materials that are not easily compostable
- Maize ears need quite a long time before decaying, so not suitable for urban compost. The leaves can be composted provided they're mixed with already composted wastes.
- Bread should be composted in moderation, if at all. It attracts rodents, and the chemicals in processed bread may slow down the composting process.
- Eggshells in themselves are not biodegradable, yet they can be added if crumbled; they're very calcareous (and contain nutrients) and so can reduce the acidity of the compost. You can also add them crushed after decomposition, just like mussel or oyster shells.
- Citrus skins (free of chemicals): they'll decompose very slowly but you can add small bits after having let them dry in the sun.
- Hair takes a long time to decompose. It may decompose faster in a vermiculture.
[edit] Materials that can't/shouldn't be composted
In most cases, animal products (meat in particular) will attract rats. Other products contain too much fat and will not degrade easily : frying oil and sauces can be dumped into a pit for greasy wastes.
- Meat and dairy products attract rats and produce foul odors while decaying.
- Rice can harbor dangerous bacteria while decaying. It should not be composted.
- Grease and fat will produce foul odors while decaying and will halt the composting process. They should never be composted.
- Dog and cat excrement can contain parasites. They should never be composted.
- Fruit peels that have been treated with chemicals contain pesticides that are toxic for ground invertebrates.
- Couch grass
- Witchgrass
- Dog grass
- Grass that's been treated with chemicals
- Diseased plants (should be burnt or disposed)
- Walnut trees produce a compound known as juglone; this compound is toxic to other plants and trees. Do not compost walnut tree components.
- Rhubarb leaves
- Vegetal cuts and branches (a few branches will naturally aerate the compost)
[edit] How to start
Put the compost bin in a half-shaded level corner of the garden, not too far from the house and make sure you can easily open the door to check the state of decay.
Keep a pail in your kitchen to collect your cooking scraps for some days. When it's full, dump its contents, into the compost bin and turn with the rod to aerate; spread dry material (lawn, leaves, straw...), if the weather is dry, water a little.
A good criteria to check its working fine is to raise the lid after a few days: it mustn't smell; if it does, make sure it's not too moist. In case the compost is too moist, add dry materials (carbon), in the opposite case you'll see white dry rots, then add a little water.
[edit] Using compost
[edit] Cropping
It's not always easy to get the compost out through the bottom panel, then unmold it, this will enable you to clean the slots at the back.
When the compost is ready, it is really dark brown and smells of forest humus, there are no worms and looks like fine garden soil. This will take from 6 to 12 months. You can then mix it to the surface soil.
If you choose to use it before, mind there'll still be undigested bits and worms too, so don't let it be in contact with plant roots or seeds as it's too strong. Just spread it on the ground and mulch.
After a year the heap will be about 1/3 of its initial volume.
Diverse uses:
- as organic fertilizer, compost improves the soil's structure
- as mulch, compost keeps the soil moist and free of weeds
- as potting soil for houseplants (mixed)
- as lawn top
[edit] Additional benefits
Even if the compost output is low, you will notice a decrease in the amount of kitchen scraps disposed of in the solid waste stream. The compost bin will be an efficient way to dispose of these types of wastes. In areas where curbside garbage disposal charges by the size of the bin provided, one may be able to save money by downsizing if enough waste avoids the bin altogether.
[edit] Community composting
Composting has long been a rural practice. Fortunately, things are changing ; in Montreal for instance you can reduce your garbage by 75% thanks to composting and recycling, and even more with reusing!
In a city, you may have to go out or walk downstairs into the yard, but it's worth it when you consider our landfills! The compost will have to be aerated with a shovel or a fork. So it's a good idea to have an air tight kitchen plastic bin not to have to go to the composter everyday. The composted matter (at the bottom) can be cropped in Autumn, decomposition is much slower in Winter but will speed up in Spring. Even if you don't have a garden, you may know somebody who does and will be happy with this rich soil!
More and more local communities launch programs and initiatives[1] to collect and use community compost[2].
[edit] Restraints to urban composting
Anyone who wishes to start composting in a city must bear in mind that it doesn't simply means letting one's scrpas rot in a box outside. Decay is an anaerobic process and this type of composting produces methane and hydrogen sulfide that are greenhouse gases as is the case with landfills.
If you do it wrong, you can attract insects, wasps and the smell may disturb your neighbours. In the country, that's not a problem but composting in a city requires even more care.
Here are some important tips to make your task easier:
- Cover potentially wastes matter with a thin layer or matter rich in carbon (straw, shreds)
- Don't dump large quantities of wastes that are not easy to compost
- Cut the scraps in small bits
- Don't let your compost become dry (it may soon do if on a balcony sheltered from the rain). If your composter is small (less than 65 gal), you may have to insulate it to allow the temperature to raise. With large community heaps (more than 300 gal), temperatures will often raise up to 140° F. A compost thermometer will allow you to check how microbial life fares. High temperatures make it healthy by killing pathogen agents such as nematodes, adventitious roots, plant and human diseases. Too much water asphyxiates aerobic microorganisms and will cause the heap to stink. If this happens, aerate the heap with a fork or a shovel. Do not dump too much lawn unless you let it dry before to prevent fermentation, the volume will also be smaller when dry.
- If you have lots of compostable scraps (more than 2 persons), be aware a small pail will get full soon and clutter your balcony
- If you live in a duplex, invite your neighbours to participate
- Keep a list of compostable products near at hand
- Remeber to be patient.
The alternative to urban compost is vermicomposting; using worms speeds up the process.
[edit] See also
[edit] Internal links
[edit] External links
- Community compost and regulations
- a compost guide
- Garden Organic
- vermicompost at the Encyclopedia of Earth
[edit] References
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