Hot Compost

Latest Update 6th March 2017.

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.
    • A cubic metre (1000 litres) of mixed organic waste is required to generate enough internal heat to quickly decompose the composting ingredients.
    • The heat generated by thermophilic microbes in the centre of such a heap kills plant pathogens and unwanted weed seeds.
    • 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 65C.
  • The speed of this process, and the way pests are removed suits my garden very well, but a cubic metre of 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 required by the Berkley method, the outer layers of the heap don't reach the required temperatures, but they do insulate the centre of the heap so that it can.
  • What I have done is to 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 (400 litres) in a shorter time (15 days in summer).
Check out my blogpage for detailed instructions on How to Make Hot Compost.

Building a Hot Compost Bin.
  • To mimic the heating effect of the larger heap a much smaller heap can be insulated using a home made insulated bin.  To get the required level of insulation, I used 2 layers of 60mm thick polystyrene foam inside the roof and sides of my bin.
  • The bin's construction allows the walls to be easily split into two pieces after the roof has been removed.  The two separated segments can then be pulled away from the heap and reassembled in a new position.
  • 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 65C, and I use a stainless steel thermometer with a 500mm probe to monitor the heap's temperature. 
Check out my blogpage for detailed instructions on How to Build a Hot Compost Bin.