Composteurs de jardin
Un bac à compost que le compost ne peut pas détruire
Le compost détruit ce qui le contient. Les bacs PolyBrick® n'en sont pas affectés : aucune pourriture, aucun traitement, aucun remplacement, et des joints ouverts qui laissent le tas respirer.
Pourquoi PolyBrick est adapté ici
Il y a une ironie particulière dans un bac à compost en bois. Le tas qu'il contient est une machine à décomposer la matière organique, et le bac est fait de matière organique. Les palettes tiennent deux ou trois ans. Le bois traité dure un peu plus longtemps et met des produits de préservation au contact d'un compost destiné à être épandu sur des cultures alimentaires.
PolyBrick n'est pas un substrat pour le tas. Il ne pourrit pas, et le matériau est inerte : rien ne migre du bac vers le compost. Il est résistant aux UV, de sorte que la face exposée au soleil ne devient pas cassante pendant que la face ombragée reste humide.
L'autre avantage est pratique : les blocs s'assemblent par emboîtement sans fixation, ce qui permet de démonter un bac. Quiconque a essayé de retourner un tas ou de vider un bac par une petite porte comprendra pourquoi c'est important.
Applications adaptées
- Bacs à compost individuels de jardin
- Systèmes à deux ou trois bacs en rotation
- Bacs à feuilles mortes
- Compostage collectif et de jardins partagés
- Stockage de tontes et de déchets verts
- Bacs à fumier et stockage de lisier solide
- Stockage de copeaux de bois et d'écorces
- Projets de jardins scolaires et communautaires
Synthèse technique
| Assemblage | Emboîtement par encliquetage. Sans outils, sans mortier, sans fixations |
| Accès | Les rangées frontales se retirent pour ouvrir le bac lors du retournement et de la vidange |
| Aération | Construire avec des espaces entre les blocs pour que l'air atteigne le tas à travers les parois |
| Base | Ouverte sur le sol, pour que vers et micro-organismes puissent coloniser le tas et que le liquide s'infiltre |
| Contact | Inerte. Aucune migration vers le compost destiné aux cultures |
| Matériau | Polypropylène 100% recyclé, résistant aux UV, fabriqué durablement dans l'UE à partir de polymères recyclés |
| Durée de vie | 25 ans sous garantie |
| Entretien | Aucun. Un rinçage à l'eau si vous le souhaitez ; c'est tout ce qu'il faut |
Construire pour laisser respirer
Un tas de compost a besoin d'air. Sans lui, le processus devient anaérobie : plus lent, moins chaud, et générateur de l'odeur aigre qui décourage beaucoup de gens du compostage.
Montez les parois latérales avec des espaces délibérés entre les blocs plutôt qu'en paroi pleine, afin que l'air circule à travers les murs sur toute la hauteur du tas. C'est le même principe qu'un bac à lattes en bois, sans que les lattes pourrissent.
Laissez la base ouverte sur le sol. Vers, champignons et bactéries colonisent le tas par le bas, le liquide s'infiltre au lieu de stagner, et le tas reste en contact avec la terre dont il est issu.
Pourquoi trois bacs valent mieux qu'un
Un bac unique est un endroit où mettre les déchets de jardin. Un système à trois bacs est un processus, et il produit nettement plus de compost utilisable avec moins d'effort.
Le principe est simple : le bac un reçoit ce que vous apportez maintenant, le bac deux contient ce que vous avez apporté précédemment et qui est en cours de décomposition active, le bac trois contient le compost fini prêt à l'emploi. Quand le bac trois est vidé, tout avance d'un cran, et le fait de déplacer la matière d'un bac à l'autre la retourne et l'aère, ce qui accélère l'ensemble du processus.
Comme le système est modulaire, vous pouvez démarrer avec un seul bac et en ajouter d'autres au fur et à mesure que vos volumes augmentent, sans vous engager sur l'ensemble dès le départ.
How it goes together
- Choose a level spot with reasonable access. You will be wheeling barrows to it in all weathers, so a route that is not across wet lawn is worth having.
- Clear the ground and level it. Leave the base as bare soil rather than paving it, so the heap stays in contact with the ground.
- Lay the first course and check it level in both directions. Everything above follows it.
- Build up the back and sides in courses, leaving gaps between blocks for airflow, and staggering the joints between courses.
- Build the front as loose, stackable courses that lift out rather than as part of the structure. This is your access.
- Where you are building multiple bays, share the dividing walls between them.
- Cap the top course if you want a finished edge, and leave the top open or cover the heap with a sheet or old carpet to keep rain off.
The removable front
This is the detail that makes a bay pleasant to use rather than a chore, and it is where most bought bins fail.
Build the front wall as courses that simply lift out. Fill the bay with the front in place, then remove the courses one at a time as you dig the heap out, so you are always working at a comfortable height with the face of the heap open to you.
Compare that with a plastic dalek bin, where finished compost is at the bottom, under everything you have added since, behind a hatch the size of a letterbox. The removable front is the single biggest reason people actually turn their heaps.
Sizing the bay
Bigger heaps work better. A heap needs enough mass to hold heat, and a small bin loses it to the outside faster than the process generates it, which is why little bins produce cold, slow compost.
Around a cubic metre is the usual working minimum for a heap that heats properly. Below that, composting still happens, it is just slower and stays cooler, which means weed seeds and roots survive it.
Do not go so wide that you cannot reach the middle with a fork. Depth front to back is more useful than width, and if you have the space, another bay beats one enormous one.
Muck heaps and green waste
The same structure works for manure storage, grass clippings and wood chip, and for those the material advantage is even clearer, because these are wetter, heavier and harder on a container than garden compost.
For muck heaps, check what applies to you on storage siting and run-off before you build. Rules on storing manure near watercourses, ditches and boreholes vary, and the position of the heap matters more than the bay it is in.
Get it right first time
The one thing worth knowing: put it somewhere you will actually walk to.
The most common composting failure is not technique, it is distance. A bay at the far end of the garden, across the lawn, behind the shed, gets used enthusiastically in spring and abandoned by October when it is dark and wet.
Site it somewhere on a route you already take, with a firm approach underfoot. Slightly less tidy and considerably more used beats beautifully hidden and full of nettles.
Ask our engineer
Questions about bay sizing, multiple bay layouts or muck heap storage? Ask below, or get in touch directly.
Common Questions
Why use plastic blocks for a compost bay instead of wood?
A compost heap is a machine for breaking down organic material, and a wooden bin is organic material. Pallets last two or three years, and treated timber puts preservative in contact with compost you may spread on food crops.
PolyBrick does not rot and is inert, so nothing moves from the bay into the compost, and it is UV stabilised so the sunny side does not go brittle.
Does a compost bay need gaps for airflow?
Yes. A heap without air goes anaerobic, which is slower, colder and produces the sour smell that makes people abandon composting.
Build the side walls with deliberate gaps between blocks so air moves in through the walls along the full height of the heap. It is the same principle as a slatted timber bay, without the slats rotting.
Should the compost bay have a base?
Leave it open to bare soil. Worms, fungi and bacteria colonise the heap from below, liquid drains away instead of pooling, and the heap stays in contact with the ground.
Paving underneath cuts the heap off from the organisms that do the work.
How big should a compost bay be?
Around a cubic metre is the usual working minimum for a heap that heats properly, because a heap needs enough mass to hold heat and small bins lose it faster than the process generates it.
Below that, composting still happens but stays cool and slow, which means weed seeds and roots survive. Do not go so wide that you cannot reach the middle with a fork.
How do you get the compost out?
Build the front wall as loose courses that lift out rather than as part of the structure. Remove them one at a time as you dig the heap out, so you are always working at a comfortable height with the face of the heap open.
It is the single biggest reason people actually turn their heaps, compared with a bin where finished compost sits at the bottom behind a small hatch.
Is a three bay system worth it?
It turns composting from storage into a process. Bay one is what you are filling, bay two is actively rotting, bay three is finished and ready to use. When bay three empties everything shifts along, and moving material between bays turns and aerates it, which accelerates everything.
Because the system is modular you can start with one bay and add others as volume grows.
Can I use it for a muck heap or grass clippings?
Yes, and the material advantage is even clearer, because manure, clippings and wood chip are wetter, heavier and harder on a container than garden compost.
For muck heaps, check what applies to you on storage siting and run-off before building, since rules on storing manure near watercourses, ditches and boreholes vary and the position matters more than the bay.
Does the bay need a lid?
Not structurally, but covering the heap helps. Keeping heavy rain off stops the heap becoming waterlogged and cold, and retains warmth.
A sheet, a board or an old carpet over the top is enough, and it can be lifted off when you add material.
Will it need any maintenance?
No. There is nothing to rot, treat, stain or replace, and no fixings to work loose. Rinse it down if you want to, but that is the extent of it.
The blocks carry a 25 year warranty and can be dismantled and reused elsewhere if you reorganise the garden.
