HOTBIN Compost Bin or a Wormery?

Friday, 4 July 2014  |  HOTBIN Composting

Worms and Composting

Choosing Between a HOTBIN Compost Bin or Wormery

wormery or compost bin

Worms will appear in the HOTBIN naturally, usually in the cooler base layer where they are able to survive [see FAQ on Worms in My HOTBIN].
 
However if you are trying to choose between the HOTBIN and a wormery there are a couple of things to consider.
 
Whilst wormeries offer the benefit of vermicompost (perceived as a higher quality of compost), wormeries are run at a lower temperature which means a lot of the benefits offered using hot composting will be lost. This means fewer types of waste can be added, weed seeds will not be destroyed and compost will take a lot longer to produce.
 

Could I Use the HOTBIN as a Wormery?

  1. Yes. There are two options for running the HOTBIN as a wormery - each has pros and cons. Run the HOTBIN as usual, i.e. hot (40-60°C) in top layer, warm in the middle layer (20-40°C) and cool in the base layer (10-20°C). The worms will migrate and stay in the cool and warm zones. You get the best of both worlds – fast bacterial decay and worms to help finish eating the waste in the bottom.
  2. Keep Valve Open: This will prevent the temperature rising above 30°C. The worms will not migrate into the top layer and work with the mesophilic bacteria that thrive in the 20-40°C temperature range.

Considerations of Running HOTBIN as a Wormery

  • Compost takes Longer: A wormery operates at a lower temperature enabling the worms to survive. So if you choose to run the bin with the valve open at 30°C bear in mind that you will be waiting significantly longer for compost than if you were using the HOTBIN to hot compost.
     
  • Seeds are not Digested: Worms will also ingest small seeds that are often not digested. Usually in the HOTBIN seed germination would be killed off by the high temperatures however this may not happen when running at a lower temperature.
     
  • Less Food Waste Can Go In: Worms dislike acidic food stuffs which means that items which would normally be ok to compost in the HOTBIN such as citrus fruit peel (orange, lemon, lime) and also onions will need to be excluded.
     
  • Vermicompost and Soil Benefits: Worms can also leave behind rich vermicompost along with mucous deposits from the worms gut digestate which some studies have shown to be beneficial to soil fertility.
     

Is Vermicompost better than Compost?

There are claims that vermicompost is “finer texture”, “more nutritious” and “better” than compost.

The main difference is that vermicompost contains worm gut enzymes and gut mucus which is used to help the solids slip out of the gizzard tract. Some studies indicate these substances have beneficial properties for soil bacteria and the root system. The texture of vermicompost is finer.

All compost decays to humus which is chemically and structurally the same. Vermicompost is finer initially because worms only eat tiny pieces of soft partially decayed food waste and these small bits are excreted as even smaller pieces. Woody twigs etc are rarely added to the wormery (because worms will not eat them). If the same items were added to both bins - the end products would be similar. It is often stated that vermicompost is more nutritious than ordinary compost.

This is true but can be misleading - vermicompost is more concentrated but you get less of it – the net result is always the same. Example: If 1Kg of food waste contains 0.3% nitrogen, it contains 3g of nitrogen. If the waste is converted to vermicompost or compost, each contains the same 3g of nitrogen (see first law of thermodynamics):

  • 1Kg of food waste produces 300g compost containing 1% N, ie 3g
     
  • 1Kg of food waste produces 30g of vermicompost with 10% N, ie 3g

You can either have 3g of nitrogen by spreading 30g of ‘concentrated’ vermicompost or 300g ‘diluted’ compost.

We can find no evidence that the chemical structure of the final humus left after both worm or bacterial composting is completed are any different chemically or physically.