1.5 million tons of organic material were thrown away in 2019-2020 (1). Composting is an easy ecological solution to reduce the amount of organic waste going to landfills or incineration.
This practice reduces the multiple negative impacts of transporting and disposing of waste materials: air, soil and water pollution, not to mention the effects on human health, fauna and flora.
Putting back in the soil organic waste
Naturally, organic matter decomposes quietly when exposed to the air. With time, it forms a soil that allows nutrients to return to the soil. Composting accelerates this decomposition.
Many organic materials, representing up to 47% of the content of our household garbage, can be composted: fruit and vegetable peels, coffee grounds, dead leaves, etc. With minimal maintenance, the compost is ready within a few months and then becomes a high-quality amendment for flower beds, vegetable gardens, flower boxes, lawns, etc.
Don't forget: although many municipalities offer brown bin collection of organic materials, it is also possible (and ecological) to do it on site! Some municipalities offer information on this subject and sometimes even composters. Contact your municipality to find out about these programs or to propose their implementation.
Putting it into practice
"Composting is a process of biological transformation of organic matter, in the presence of water and oxygen. Fermentation takes place and micro-organisms transform the waste to form, after maturation, compost: a stabilized product, hygienic and rich in humus, very useful in the garden” (2).
How to do it?
Composting is not complicated. If you follow a few basic rules and organize yourself well, it quickly becomes a natural process.
First of all, it is important to understand that in order to decompose, organic matter requires a good level of humidity, oxygen, and a variety of residues. It is therefore important to (2):
Mix the different organic wastes together
Stir the mixture and let it breathe - to promote the action of microorganisms, and homogenize the resulting mixture
Pay attention to the humidity: the compost should not be soggy, but very humid
In practice, here are the steps to follow (3), after having chosen your composter :
Place the bin on a flat, well-drained surface that is easy to access year-round, and preferably in a location that is neither too sunny nor too shady.
Turn over the soil where the composter will be installed.
After placing the composter, cover the bottom with a row of small branches. This will allow air to circulate and improve drainage.
Alternate wet residues (kitchen waste) and dry residues (dead leaves, newspaper, straw, wood chips, etc.). It is preferable to always finish with a layer of dry residues or potting soil to avoid odors.
Initially, add mature compost, garden soil or a starter product (available at garden centers) to your waste. This will speed up the composting process. You can repeat this process as needed.
At least twice a month, turn the fermenting pile with a fork or shovel to aerate it, speed up decomposition and avoid odors.
Your composter should allow you to collect mature compost through a trap door or door at the bottom: as the waste is piled up, it decomposes at the bottom and becomes compost.
To choose your composter, here are some useful questions:
How much space do I have?
Is the look of the composter important?
What is my budget?
Are there any municipal bylaws governing the use or size of composters?
There are many models available, some of them very elegant! Most hardware stores and garden centers carry them. But why not have one made of wood by a local craftsman? It's also not very complicated to make your own composter.
If you have a large yard, you can compost "in piles": in a remote corner, simply pile up the waste. Make piles and turn them regularly to activate fermentation. The natural watering and the large surface (oxygenation) will be your advantages (2).
The essential features of the composter
A lid to protect the compost from rain and snow and to control the humidity level
Holes or openings to promote air circulation
A means of removing the final product, usually a trap door at the bottom of the composter
What to Compost?
Basically, there are two types of waste to be mixed together:
Wet, rich in nitrogen (also called green matter)
Dry, rich in carbon (also called brown matter)
To obtain an optimal maturation of the compost, it is recommended to mix about 1/3 wet materials for 2/3 dry materials.
Wet waste contains water, which is very useful for the process, but on its own, it settles and asphyxiates, generating spills of juice and unpleasant odors.
Fruit and vegetable peels and scraps
Green garden waste: wilted flowers, prunings, grass clippings, weeds (without mature seeds), etc.
Carbonaceous wastes compost very slowly if they are alone.
Tea bags, herbal tea bags and coffee grounds (with filter)
Leftover bread, rice, pasta, legumes
Crushed eggshells (contain minerals and facilitate aeration)
Dried tree leaves (they decompose faster if shredded)
Old potting soil
Straw, hay, sawdust, twigs
Pet fur and hair
Materials to avoid
Meat, fish, shellfish and bones
Fats and oils
Animal feces and litter
Weeds that have gone to seed or are crawling
Diseased plants or foliage
Vacuum cleaner bag contents
Materials contaminated with pesticides or hazardous materials (e.g. treated wood)
Worm composting, sometimes called vermicomposting, is the solution for people who don't have land on which to install a composter, or for those who don't want to use their composters during the winter. This type of composting is also very popular with children!
This method consists of producing compost with the help of red worms - a type of earthworm that is different from the worms found in the garden - which can be obtained from various places. These worms consume and digest a phenomenal amount of waste, quickly producing rich compost.
It is easy to make a worm composter. It can be installed outside, but you must provide an indoor space for the cold season because the worms could not survive.
Yard waste can be composted. But grass clippings are often too much material for a composter. The solution? Grasscycling, which consists of leaving the grass in place after mowing, is an ecological method of fertilizing the lawn. In addition to being an important source of nitrogen, grass clippings, which are mainly composed of water, act on soil moisture and help protect the lawn from certain diseases.
Several municipalities in Quebec encourage the practice of grasscycling among their citizens through awareness campaigns. Some have even adopted by-laws prohibiting the collection of grass with green waste or household garbage.
Some practical advice:
Mow the lawn regularly, at a height of about 7 centimeters (3 inches) but never less than 4 cm (1.5 inches), and when the grass is dry.
Make sure the mower blade is sharp or use a mulching blade that reduces the size of the clippings, which increases the speed of decomposition.
If the mowing was done too late, collect the grass clippings and place a 15-centimeter (6-inch) layer in the compost bin or use it as mulch.
The compost is ready!
It's quite easy to recognize mature compost: dark brown, it looks like good soil, has a good humus smell and you can't recognize any of the waste materials used (except for a few hard-to-compost materials like eggshells and pits).
How to use it (4)?
Compost is not a fertilizer, but an excellent amendment for garden soil, as it nourishes the soil, improves its structure and aeration and increases its water retention capacity. You can use it indoors or outdoors:
Mix with the top six inches of garden soil and use it around trees, shrubs, vegetables and flowers.
Mix with your planting and transplanting soil (at a rate of about one-third compost by volume).
Spread the sifted compost on the lawn, after aerating it.
To speed up the process
You will quickly learn how to make compost. To improve your practice, you need to know the factors that can influence curing time (5):
The right proportion of wet and dry matter
The size of the residues used (the smaller the pieces, the faster the process)
Proper aeration and moisture content
The method used and the volume of material composted
How to increase your chances of success?
Keep a resealable container in the kitchen in which to place your table scraps. A nice stainless steel container near the sink is very practical.
If you generate a lot of waste and have room to spare, use two composters: while the compost matures in one container, you use the other on a daily basis.
You can place waste in the composter all winter. The decomposition process slows down or stops when the pile is frozen, but it starts up again very quickly in the spring, after a good turning
Empty the composter as much as possible in the fall to make room.
If you don't have a garden, you'll be happy to donate your compost to a school or community group for use in their landscaping.
Remember: it is important to eat well, "not too much, just enough", while being careful to waste as little food as possible. So get the anti-waste reflex before you compost!
Several guides and publications on composting are available. Here are a few very complete ones, available online:
- Le compostage facilité, Recyc-Québec
- Petit guide pratique du compostage domestique, Ville de Montréal
- La valorisation organique : le compostage, Sitom Sud Gard
(1) Caractérisation des matières résiduelles du secteur municipal 2015-2018, Recyc-Québec
(2) Source: Compost : les bases du compostage, Xavier Gerbeaud, gerbeaud.com
(3) Source: Compostage domestique, Recyc-Québec
(4) Source: Réduisez votre quantité de déchets : compostez, Environnement Canada
(5) Source: Comment faire son compost?, Ville de Québec