Top 5 Common Hot Composting Mistakes

10 August 2018  |  HOTBIN Composting

Top 5 Common Hot Composting Mistakes

1. Adding Lots of Old Compost

Small amounts of old compost can be useful to inoculate a compost pile when added with fresh waste; too much however provides no positive benefit to the contents of the bin. Why? Bacteria require a food source to continue breaking down waste and producing heat as a by-product. Old compost will have already been largely broken down and lost the majority of its nutritional value for bacteria.

Basically, for bacteria it would be like eating the salad bowl and not the salad for dinner.

Top tip: Don’t start your HOTBIN with a base layer of compost from an old heap, it will have no nutritional value and may cause aeration issues in the bottom of the HOTBIN.


2. Adding all the Bulking Agent In One Go

Base layer of twigs in the HOTBIN

The bag of bulking agent (woodchip) supplied with the unit is not a “starter base” so the contents of the bag should not be emptied into the unit to start the hot composting process.

We do however recommend adding a layer of twigs in the bottom of the HOTBIN. This small layer of twigs helps create additional aeration in the bottom of the unit and helps ensure that HOTBIN is well aerated at the beginning of the process.

Ensure after this that the woodchip supplied is added into the HOTBIN every time waste is added in.


3. Not Adding Both Paper and Bulking Agent

Adding both paper and bulking agentBacteria require feeding with waste and as they break down waste they produce heat as a by-product. As well as keeping bacteria fed they also need access to oxygen. The bulking agent (woodchip) has a structure which when added in with waste creates air spaces allowing oxygen to flow easily through the contents of the HOTBIN.

Shredded paper/card help to control moisture, so although bacteria need some water to work efficiently, too much can cause their anaerobic cousins to take over. We definitely do not want that!


4. Layering Materials

In traditional compost heaps it is normal to build a compost pile in the same way you would build a lasagne - in the HOTBIN however we are more about the bolognaise rather than the lasagne! Layering materials can cause issues with aeration, so we want woodchip to be dispersed through the waste to allow oxygen to flow around the unit and paper to absorb moisture thoroughly and avoid creating a soggy, matted layer.

Top tip: So remember, mix rather than layer and mix only what’s added with the top 5-10cm (2-4 inches) of existing material. Don’t mix through the entire contents of the HOTBIN when adding waste – it will just pull the cooler maturing material back to the top and slow the process down.


5. Adding One Type of Material

Just adding grass in the HOTBIN

The HOTBIN likes a varied diet and the scientific reasoning behind this is that different types of waste are digested by bacteria at different speeds. Grass for example is very easy to digest and will rot down very quickly whilst twiggy material is much harder to digest, so will take longer. Aim to add a mixture of materials so when bacteria have finished breaking down an easy to digest material like grass there will still be other types of waste for them to work on and continue to produce heat whilst they are waiting for the next HOTBIN feed. It’s a bit like a human diet, eating foods heavy in sugar may give you a short term boost but it is better to have a mixture of food types which release energy more slowly but over a long period to keep you feeling energised for longer.

Top tip: If you add a load of grass in one feed, try and incorporate other materials along with paper and bulking agent. If you are unable to do this then next time you feed the bin give the old grass layer a quick rake to break it up a bit and this will help prevent any airflow issues.