Hot Composting or Cold Composting? Which Way and Does It Matter?
Hot-composting or cold-composting –
which way and does it matter?
When you decide that you will have a ‘go’ at composting, typically your first decisions will be centred around the answers to such questions as,“What kind of bin shall I use?” “ Where shall I put it?” “How much time do I want to spend on this project?”
You will also have to decide if you are going to be ‘hot’ or ‘cold’
- When Hot Composting, the temperature of your pile needs to range from 140^ F to 150^ F (40-70C) for peak efficiency.*
- When Cold Composting, your pile will need to reach at least 6^ C (42-43F)* Colder than that and your microbes will cease working and your heap will lie dormant. The temperature will rise higher if your container is well-insulated, situated in a sunny spot and if your mix is well-balanced.
Are there added benefits to hot-composting? Well, yes there are.
- It is much faster than cold-composting.
- You can add a wider range of materials to your pile e.g. food waste that is normally ‘forbidden’.
- Seeds are killed more efficiently, preventing the spread of unwanted plants.
- Herbicides and pesticides are broken down.
- Bacteria and Pathogens are destroyed.
- It rarely smells.
- Fly eggs and maggots will be killed.
- Decomposition will continue throughout the year, regardless of the ambient temperature.
So, what are the benefits of cold composting?
- It does not require as concentrated an effort as hot composting.
- It is not necessary to amass such a large quantity of ingredients.
- It is not necessary to turn your heap every few days. In fact, many gardeners never do it.
- Your mix will lie dormant during cold weather and just start up when it gets a bit warmer.
- Small insects and worms that inhabit your bin and help in the decomposition process will not be killed when temperatures rise.
If you are in a hurry to get your compost finished and on to your garden, if you have the energy and capacity to do it and if you have sufficient ingredients on hand, you may well decide to try hot composting. On the other hand, if you are not in a hurry, if you tend to be a bit more laid back, cold composting could well be your choice.
Possible ‘down-sides’ to hot composting
You will need enough ingredients to`batch compost’, that is to make your pile all at one time. Remember, to achieve a higher temperature, you need a mass of approximately one cubic metre (yard). Anything smaller will not easily reach the desired temperature of 140-150 degrees. If you have to accumulate these materials over a period of time and then add them sporadically to your container, you will find it difficult to reach temperature as each addition will cause cooling, thus slowing down the process of decomposition.
To do hot composting, you do need to be a bit more organised than you do if you are cold-composting. Firstly, as noted above, you need to have all your ingredients on hand, ready to go. You need to be prepared to regularly tend to your pile, to turn it over on schedule, to keep it well oxygenated and to ensure that has the right degree of moistness. If you decide to embark on the 3-bin system of composting, you will need to start collecting your second load of ingredients ready for when you turn your first batch into your ‘curing’ bin.
You probably need to be reasonably fit and to be willing and able to toss forkfuls of compost willy-nilly if you are using a static turning unit. To learn more of rotating or tumbling turning units, click here.
Possible ‘down-sides’ to cold composting
It can be a long-winded process and if you have lots of garden waste, you will need to provide storage space until you can deal with it. Hot composting does turn over your waste with some speed so that you do not take up what may be precious garden area.
The list of ingredients that you can add to your heap will be limited. For instance, cooked food, meat, dairy products, weeds in seed, diseased plants, pernicious weeds, are just a few examples of items to avoid in a cold heap.
Your pile can get smelly if not tended properly or if the ingredients are out of balance.
Flies and maggots may proliferate if care is not taken.
To sum up – hot composting is more work, but you can process a wider variety of waste with greater speed. Cold composting is more relaxed and takes up less of your time, but you are limited in what you can safely add to your pile and the whole process takes a lot longer.
The choice is an interesting one, but compost is compost and the general consensus seems to be that the quality of the finished product from either system is probably dependent on factors other than temperature.
Resource: “How to Make and Use Compost” by Nicky Scott. Published by Green Books, 2009