Using Old Compost to Start a HOTBIN

Using Old Compost to Start a HOTBIN

Can You Use Old Compost to Start the HOTBIN?

Using Old (Mature) Compost

The term ‘old’ may be the confusing factor here. Old compost, or mature compost is waste that has finished breaking down and is ready to use.

Within old compost there will still be a population of bacteria, however with no access to fresh waste it is effectively dormant.

Compost Inoculation Explained

Compost inoculation is the process of adding bacteria to kick-start the population growth. Bacteria are an essential part of the composting process and adding a handful of ‘old’ compost to start (inoculate) a HOTBIN will simply add more bacteria into the waste. It is not however essential as there is usually enough bacteria in the air (as spores), and on the fresh garden/food waste going into the HOTBIN to start the composting process.

Adding old compost in large quantities should be avoided as this could lead to problems with blocked aeration in the waste which will stop the HOTBIN working aerobically.

The fresh waste you add into the HOTBIN will already have a population of bacteria within it, indeed with the right conditions (food, warmth, water and oxygen), 1 bacterium could multiply into 8 billion bacteria in 13 hours. Only a small number are needed to start the composting process (inoculate the bin), which is why it shouldn’t be necessary to add old compost.

Should I Use Compost Accelerators?

There is no benefit to using commercial inoculants / powders in the HOTBIN to kick-start the composting process. The best way to kick-start the process is to create the perfect base layer. As long as the HOTBIN is aerobically composting commercial inoculants will have little effect on the speed of the HOTBIN.

Using Partially Composted Material in the HOTBIN

If you have a heap of partially composted (still decomposing) waste possibly from an existing compost heap or bin, that you are looking to add to your HOTBIN there are a few things to note.

When creating the base layer in your HOTBIN this partially composted waste can be used but it must be mixed with fresh easy to digest waste, shredded paper and bulking agent.

We recommend a split of 50/50 for partially composted waste/fresh waste when adding this material into the HOTBIN, however bear in mind that the more degraded the waste is the higher the quantity of fast/easy to digest material will be required with it to achieve temperatures above 30°C.

Therefore, whilst this might be a useful starting point for creating your base layer and getting your HOTBIN up and running quickly, we would not recommend filling your HOTBIN with more than half way with partially composted waste as you would need the same amount, if not more of fresh waste.

By leaving half of the HOTBIN empty you’ll have enough space in which to add additional fresh waste little and often. We recommend a minimum of 5kg (two standard council food caddies) of fresh waste is added every week to ensure bacteria is fed with enough waste to sustain hot composting temperatures.


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