Accueil > Resources to understand and act with the compost > Use


mardi 3 mai 2022, par La graine

Toutes les versions de cet article : [English] [Français]

Key steps for using the collective composter. Notice to members, conditions of the compost bin, shredded material, refusal of contributions...


Member instructions
Conditions of the compost bin
What we put or not

Using a composter requires understanding a few key steps from the deposit of bio-waste to obtaining compost.

In this part, we are going to talk about authorized or unauthorized deposits. This entirely depends on the choice made for the local composting site.

Indeed, theoretically, all organic matter decomposes. However, for various reasons [1], choices can be made on the deposits authorized or not.
A part at the end deals with the issues / difficulties / potential discomfort of certain deposits.

Member instructions

Here is an example of instructions to send to new members (or a reminder ☺).
The email makes it possible to contact all the users to solicit them more easily if necessary (manipulation or other).


Here are the editable sources.

In word processing format (made on Libre Office).

Conditions of the compost bin

Compost has several conditions. We will see them in chronological order. Bins can be rotated to allow for multiple conditions at the same time.


There is only one bin being filled at a time. Compliance with the instructions, which can be found later, is important.

In the example above, of instructions sent, the deposit bin is always the same to simplify the use of the composter.

After depositing your bio-waste, you add a little amont of sawdust on top. The amount of sawdust is approximately that of the deposited volume.
The sawdust contains carbon (C). Bio-waste mainly contains nitrogen (N). The C/N ratio is an indicator of the decomposition of organic matter (also called humification).

As it dries during this and subsequent periods, the volume can shrink by 40-60%, largely through loss of moisture from the organic waste.

Here is an example of a sign to put on the current bin. (To be laminated to resist bad weather).


For people who master vector drawing (svg made on Inkscape).

A simplified format for word processing (made on Libre Office).


Once a bin is filled, it is put in a condition of maturation by stopping the deposits.
In the example above, of instructions sent, the deposit bin is then transferred, to mature it in the next bin. This has two advantages : aerating the compost and keeping the same deposit bin.
During the maturation period, bacteria, fungi and other organisms (micro-organism, macro-organism, earthworms, woodlice, etc.) degrade the elements that are there.
At the heart of the compost, the temperature can rise to 70°C (158°F) with all this activity.

Here is an example of a sign to be affixed to the maturing bin. (To be laminated to resist bad weather).


For people who master vector draing (svg made on Inkscape).

A simplified format for word processing (made on Libre Office).

The turnaround

It is interesting to transfer a maturing bin to an empty bin. By doing this, the decomposing material is loosened and aerated.
Air supply allows aerobic bacteria to proliferate and aid in final degradation.

The distribution

After 9 to 10 months of maturation, the compost is ready to be distributed ! We recognize a mature compost by its dark brown color, its lumpy consistency and a good woody smell.
For compost distribution, you can :

  • communicate with the members of the collective composter ;
  • communicate with neighbors who have a garden ;
  • deposit it in a collective garden ;
  • donate it to the green spaces department ;
  • or resell it if you are constituted in a form legally allowing it.


It is important to put sawdust and not whole branches, which will have a hard time decomposing and which do not absorb odours.
To obtain sawdust, it is possible to ask the green spaces department, a sawmill or even the waste disposal centre.
If you do not have sawdust available, it is possible to add dead leaves. Once the leaves are dead and browned, the nitrogen level decreases and they are mainly composed of carbon.

What we put or not


There may be local variations in the instructions, involving several parameters, such as quoted in the introduction to this section.

Here is an example of a sign to be affixed. (To be laminated to resist bad weather).

In png

In pdf


For people who master vector drawing (svg made on Inkscape).

A simplified format for word processing (made on Libre Office).

Deposits that raise questions

As stated before, all organic matter decomposes. However, for various reasons, choices can be made about the desired intake or not.


Eggshells may have difficulty breaking down. Well crushed, they will not cause any problem.
The calcium will neutralize the pH of the compost (if you accept citrus fruits, it’s handy) and the eggshells will bring magnesium and phosphorus to the future soil.

Citrus peels

For citrus fruits, the question that arises is the one of the acidification of the pH of the compost. However, in a quantity that is not excessive, this will not cause any concern. Once cut into small pieces, the peelings will mix well in the compost, to decompose more evenly.

Meat, fish, shellfish

These three items can attract rodents and pets or strays. This can be avoided by an anti-rodent wire and by « hunting » for the slightest hole in the composter.

Fish and shellfish can be particularly fragrant (especially in quantity after festive periods).

In addition, for meat there is the question of the E Coli bacteria. It proliferates between temperatures between 7°C (45°F) and 50°C (122°F), the optimum temperature being 37°C (99°F). A temperature of 70°C (158°F) is recommended to get rid of it. [2]

In all cases, there is a higher pathogenic risk.


The shells of walnuts, hazelnuts,..., decompose very slowly. However, they contain valuable nutrients (magnesium, phosphorus, etc.) and their presence can improve the aeration and drainage of the compost.
Depending, among other things, on the use of the compost (planter or garden), we can accept this contribution or not.
If you don’t use them in the compost and you have a lot of them, it’s possible :

  1. to make mulch ;
  2. use them at the bottom of the flower pot to drain the water ;
  3. to use them in garden paths as « stepping stones »...

Note that some shells, such as almonds, decompose quite well.


The presence of small core (such as olives or cherries) in the compost will not really pose a problem and will not be too visible.
Peach and avocado pits break down quite slowly.

Papers and Newspapers

Theoretically, papers and newspapers can be accepted. It adds carbon.
It will however be necessary to pay attention to the type of paper (untreated, not plasticized, without shine and without heavy inks...).
We can also favor the recycling of papers and newspapers to reduce the exploitation of forests.

Grass clippings

Grass clippings can be refused for two main reasons. It takes up quite a bit of space and the grass is high in nitrogen.
The nitrogen supply can be neutralized by the carbon content of the sawdust.
We can accept sporadically or not a layer not too thick (5 to 10 centimeters / 2 to 4 inches).
You can also compost the grass separately (in a pile or in a container), so as not to take up too much space.


Shells decompose with difficulty, but provide mineral elements over the long term through wear. Depending, among other things, on the use of the compost (planter or garden), we can accept this contribution or not.

Bioplastic bags

If bioplastic bags are indicated as biodegradable, depending on the processing time, this may not be enough.
A study by the International University « Marine Litter Research Unit of Plymouth », published in the journal « Environmental Science and Technology » [3], shows biodegradable bags still intact three years after being abandoned in the wild.

Animal litter

The litters are not all vegetal, which would be strongly preferred for the balance of the compost. In addition, there may be pathogenic elements, such as toxoplasmosis, dangerous for pregnant women and immunocompromised people.

Dry toilets

For reasons of pathogens, odors and user comfort, we avoid feces. We will compost this elsewhere and most often in our own garden. The composting time is also longer (18 months minimum).

Edible vegetable oil

Oils can reduce air circulation by occupying spaces and can attract rodents. They contain lipids which are rich which could feed species in the compost and can, in theory, be accepted in very small quantities.
On the other hand, frying oils are in larger quantities and do not be accepted through a conventional collective composter.

Hair and nails

Hair and nails (and animal hair) are good compost activators, but the use of treatments (dye, bleach, varnish and other products) can raise questions. In this regard, a guide on toxicity (Cosmetox Guide : health risks of cosmetics [4]) was made a few years ago, but is no longer up to date.

[1type of composter, mix of inputs, group of users, end use, maturation time, desired handling, contract of the master composter and time to be spent on the site...

[4If you have a link to a pdf version, it is welcomed !


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