Hot Compost

Latest Update 10th July 2021.

Making Hot Compost.
  • I use the Berkley (University of California) method of making compost.  It has 3 main features which separated it from cold composting processes.
    1. A minimum cubic metre (1000 litres) of mixed organic waste is required to generate enough internal heat to quickly decompose the composting ingredients.
    2. The heat generated by thermophilic microbes in the centre of such a heap kills plant pathogens and unwanted weed seeds.
    3. The compost needs to be maintained in an aerobic state for at least 18 days for it to hold a temperature of between 55C and 70C.
  • The speed of this process, and the way pests are removed suits my garden very well, but a cubic metre of organic waste is barely practical, and is certainly not convenient in a small garden like mine, so I have adapted the technique to suit a smaller batch of about 400 litres. 
  • In the typical cubic metre compost heap, the outer layers don't reach the required high temperatures, but they do provide insulation so that the centre of the heap can generate its own heat. 
  • My design effectively replace this outer layer with a 120 mm thick layer of expanded polystyrene foam.  It enables me to process a much smaller volume of compost (about 400 litres).
  • I usually produce a batch every month (about 3000 litres annually), and gradually use it before the next batch is finished.  More
Building a Hot Compost Bin.
  • To mimic the insulating effect of the outer layers of a cubic metre compost heap a much smaller batch (about 400 ltres) can be satisfactorily processed using a home made insulated bin.  
  • To maintain the required temperature, the bin must be insulated with 120mm thick polystyrene foam in the walls, base and roof.
  • The bin's construction allows the walls to be easily split into two segments each comprising 2 wall panels.  The roof and base are very light, and its easy to dismantle the bin into its component parts to be reassembled nearby
  • By throwing the compost through the air from the old pile into the bin in its new position, the compost is aerated and mixed thoroughly. The aim is to keep the compost temperature in the range 55C to 70C, and I use a stainless steel thermometer with a 500mm probe to monitor the heap's temperature....More