Vermicomposting vs Hot Composting

Remember when you thought all composts are equal and then you came across terms like vermicomposting, hot composting or traditional composting. (We’ll have mercy and won’t mention leaf mold, Bokashi and Quick Return just yet)

After discussing vermicomposting and traditional composting here we are now going to dig a little deeper and break down (if you’ll pardon the puns) how hot and cold composting compare to vermicomposting.

After reading this article you’ll be able to decide whether either or both methods are useful for where you live and what to do next if you want to implement them in your place. And we will do our best to shed some light on what ‘hot’ and ‘cold’ or ‘active’ and passive’ mean in the world of composting.

Feel the heat

As we’ve already seen, the most common form of traditional composting would be the cold, or passive, method. This simply involves adding garden and kitchen waste to a bin or pile. To avoid ending up with a smelly, soggy mess it does require some maintenance – periodically turning with a garden fork or spade to aerate and checking the moisture levels.

Hot composting is more involved, in terms of planning, ‘feeding’ and maintenance.

Size matters

In cold composting, the size of your bin or heap is only limited by the size of your garden.

Hot composting, by contrast, has stricter parameters. Your bin should be no smaller than a 3-foot cube, although some recommend 4-foot cubed is even better. Although they can be bigger, this seems to be the optimal size in terms of ease of maintenance.

It is possible to hot compost without a bin, but can be more complicated and will require a larger area, so for the purpose of this article we will assume a bin is used.

There are a number of different options to buy an insulated hotbin or, of course you can build your own.

The other size issue relates to the size of the waste you add. As long as you’re only adding appropriate waste, with cold composting there’s no real restriction.

For hot composting you need to chop or shred your cuttings and trimmings into smaller chunks, ideally no more than 5cm.

Feeding the beast

In cold composting you can continue to add your garden and kitchen waste as it comes, simply turning and mixing each new batch.

For hot composting you put everything into the bin in one go – you don’t generally keep adding. You also need to give some thought to what you add, and how. 

To achieve and maintain the temperatures needed for hot composting, it is important to get the nitrogen level right. This is done by balancing the carbon- and nitrogen-rich material. The optimum mix is two parts carbon matter to one part nitrogen. Carbon or brown matter can include dry leaves, twigs and straw, while nitrogen-rich, or green, matter might be grass cuttings, plants or vegetable scraps.

Advice seems to vary as to whether the best results come from layering the brown and green material, or simply mixing it together. You might also choose to add a few handfuls of ‘finished’ compost to the mix as a kind of accelerant. The final step is to add water.

An obvious downside to this method is that you will probably still accumulate organic waste after you have loaded your bin. With a cold or passive compost heap you can simply add this to the pile. For hot or active composting you will need to store this material to use once your first batch of compost is ready. For this reason most people tend to have one or two additional bins – to store waste until needed, and possibly to have a second bin on the go.

Turn and turn again

A cold compost pile needs turning periodically to keep introducing air into the organic matter, and to allow you to check it is not to dry or too wet.

Hot compost needs more attention and temperature monitoring. Ideally turn it twice a week or every couple of days to keep the temperature up, and check the temperature with a compost thermometer regularly. If the temperature drops too much you may need to turn more frequently, or perhaps add more green material. Although do take note that adding additional waste means the process will take a little longer.  Finally, water occasionally to keep everything moist.

Time is of the essence

The big advantage of hot over cold composting is the time it takes to complete the process. Cold composting can take several months to decompose to usable fertilizer. Hot composting is far quicker, taking three to four weeks. 

Also, unlike passive composting , which tends to slow down or come to a standstill in cold weather, this active method can be done all year round, although more checking and turning may be necessary in cooler climes.

So let’s do a quick-look comparison:

Cold Composting Hot Composting
No initial outlay necessary Commercial bins are the easiest option, at least to start with, and can be expensive
Pile can be as big as you like, only limited by garden space 3-4 feet cubed is the optimal size
Organic matter can be added as is Material needs to be chopped to a smaller size
You can continually add to the pile Only one batch of organic waste can be processed at a time
Larger amount of compost produced Smaller output each batch
Low-maintenance Requires regular attention
Process can come to a stop in colder months Process can be carried out all year round
Process takes several months Process takes 3-4 weeks

So the differences and benefits of each are clear. If low-maintenance is your goal, and time is not an issue, then cold-composting is for you. While a neglected compost heap is not a happy compost heap, a bit of turning is all that is required.

For a quicker turnaround, and a regular flow of compost free of weeds and pathogens, then hot composting would be the best choice. You need to work a little harder, but you will get the finished result much quicker, allowing you to start a fresh batch and keep the flow going.

Vermicomposting vs Hot Composting

We’ve previously seen how vermicomposting compares to cold composting, so now let’s look at how hot composting fares against our worm team.

Common grounds of wormery and hot compost

  • Both processes are quicker than cold composting
  • Regular ‘harvest’ of compost
  • Can be done all year round
  • Smaller volumes compared to cold composting
  • Usually done in an enclosed container

So what are the differences?

Vermicomposting Hot composting
Initial outlay to start with Hotbins are more expensive to buy
Can be done indoors or outdoors Can only be done outdoors*
Little space required Outdoor space needed *
Little maintenance required Needs regular turning
Suitable for any ability Some strength is needed to turn
Best for plant based kitchen waste like veggie peels and scraps Can take both kitchen and garden waste
Has more beneficial microbial life
*there are some products marketed for indoor hot composting, but this is not the norm

So which Composting Method is Best?

All three systems of composting have their benefits, and if you have a decent sized garden where there is a continuous amount of garden waste to dispose of, some form of traditional composting is obviously your best bet.

Hot composting is great to speed up the composting process of garden waste, kill weeds and their seeds in the process

But if like many people you are looking to reduce landfill, and become as zero-waste a household as possible, then a worm bin might just have the edge. It is particularly suitable for plant based kitchen waste and can be done in apartments, or houses with balconies or tiny gardens, thereby contributing to a sustainable lifestyle.

Find out here how to set up a wormery at home.

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