How much waste can HOTBIN compost?

Friday, 6 January 2012  |  HOTBIN Composting

The HOTBIN is designed around a typical family (4 people) with a small garden. However it works based on a core principle of science related to heat made and lost via cooling. The amount of heat (calories in the waste the waste the bacteria eat) has to be more than the calories lost as heat via the insulated walls (small) and hot steam leaving the valve to keep the temperature above the ambient (external temperature). This means to stay hot there is a minimum amount of easy to digest food waste needed - and this is needed constantly.

It does not mean you cannot leave the HOTBIN and go away on holiday - but it does mean that while you are away it will cool down and when you get back it will take a few days with new waste to re-heat.  

Weekly minimum amount of waste needed: 

You need to add at least 5 kg per week (one medium 9 litre caddy, 2 small 5 litre caddies) to maintain 60°c. A typical 4-person household will generate 3-5 kg of food waste a week. Note: keep in mind you may need to add shredded paper or corrugated cardboard if your waste is 'too wet'.

Maximum:

You can fill the HOTBIN right to the top and leave it to compost all the way down. However there is a rare situation (normally only seen in Hotels/cafes with large daily amounts of food waste) that creates a daily maximum. Waste added will be at ambient temperature (eg 20°c) and is 'cold' compared to waste in the HOTBIN (40-60°c). The temperature of the combined old + new waste falls, then as the bacteria get to work, the temperature rises. However if you add another load of cold waste before the last lot has reheated, the waste will cool again - so it appears to be stalled. Rule of thumb - when adding food waste, add no more than 5Kgs every other day. If you have more, contact us and we will run through the options.

Not everyone will want to add all food waste, or have enough to keep a constant high temperature. The HOTBIN can be operated as a normal compost bin - just remember not to add meat, fish or diary (it will go anaerobic at lower temperatures) and read the Q&A on hot versus cold so you understand other things such as killing seeds.