Build a Hot Compost Bin.

Reviewed and updated 21st January 2021.

This is my homemade hot compost bin.  Its purpose is to make relatively small batches of compost using high temperature microbial breakdown. See making hot compost.

The unit's external dimensions are 950 x 950 x 1070mm high (lid and floor included) and it's assembled from 4 identical wall panels plus 2 identical top and bottom panels.

Recycled timber is used to make a simple exterior frame for each wall panel, and 2 layers of 60mm rigid polystyrene foam are glued together to make a single 120mm thick panel which is then bonded into position within the frame.  Each wall panel is 830mm x 830mm x 120mm (thick).

Once the glue is set, both sides of the wall are covered with heavy duty shadecloth stapled to the timber frame to protect the foam from damage.

Each sub-assembly is made by joined 2 panels together overlapping them at their corners.  They are joined top and bottom using galvanised angle brackets on the inside and galvanised flat joining plates on the outside.

Two saddle clamps are screwed into position as shown.  They help to handle the sub-assemblies when they are being separated so the compost heap can be aerated.

When the two halves are brought together, they are secured using small brass cabin hooks as shown above.

The lid and floor are made from 60mm polystyrene foam and 75% shadecloth. Two layers of the foam are laminated together using "no more nails" glue and covered with the shadecloth to improve impact resistance and add a bit of UV protection. 

Two pieces of shadecloth are cut and glued to the outside of the foam block, overlapping at the sides, so they are double the thickness of the top and bottom.

Both of these components are 950mm x 950mm x 120mm.  Their different colours are not important (they were determined by the availability of scrap shadecloth from my shed).

This picture shows the bin just finishing a batch of hot compost which usually takes 18 to 20 days to make.  

Removing and fitting the lid is very easy, and its light enough for even an old man like me to handle.  The floor is held in position by the weight of the other components.

The bin was first put into service in October 2016 and has produced a batch of compost every month since then (about 3300 litres per year).