Tyre Stack Composters

One method of making secure composters is to use old car tyres to construct a modular composting bin. This idea has been around for some time and was developed at the Centre for Alternative Technology. It makes good use of a waste product. Another approach is to join up four pallets in a square and place the compost inside. It can be covered with a piece of old carpet which encourages worms to work the whole pile. This is an adequate approach if the compost removed from the toilet is already quite well rotted.

Some useful points to consider when making and using a tyre composter:

• Radial tyres have steel wire in them making them rat proof.
• The stack should stand on a concrete paving slab or wire mesh (weld mesh) so as to prevent rats finding their way in from underground.
• Using car tyres, the volume of a stack 1.2m high might be around 0.3m³ depending on how much material gets into the rim.
• If you intend to carry out further composting of compost from a FULL ACCESS COMPOSTER toilet you may need several stacks. Four grouped together in a square would take up an area approximately 1.2m square  (4’ x 4’).
• It is inadvisable to go higher than 1.2m (4’) as the stack will become unstable.
• You must keep a record of when stacks were filled. We suggest that they are left for a few years after which the compost should be safe but we advise against the use of finished compost on food crops where the edible part is contact with the soil or might come into contact with the soil.
• When the stack is eventually dismantled the tyres will have to be shaken or stood on edge to get the compost out of the rim. Low profile tyres are better since the rim is very shallow.
• In the drawings, notice how the bottom tyre is partly underground. This means that any liquid from the composting process disappears into the ground without risk of human contact.
• If using a concrete paving slab it may be wise to drill some 10mm diameter holes around the tread of the lowest tyre to admit soil organisms e.g. worms. Manure worms can also be added from an existing muck heap and will speed up decomposition.
• Some rain ingress into the stack is useful. The lid need not prevent this.
• The fence keeps children and animals away and prevents the stack from being knocked over. Pallets make good fences or old corrugated sheeting.