A cold compost heap can take months or even years to reach perfection.
The good news is that you don’t have to wait that long. In fact one composting system produces finished compost in just 14-21 days. (You’d ideally let it mature for a while before using it for the first time!)
If you’re as impatient as I am, and are wondering how to speed up your compost heap, you’ll find the following 16 tips will help you really accelerate the process!
1. Add a layer of branches at the bottom
Placing a layer of twigs or bottoms at the bottom of your compost pile traps air inside the compost pile. This enables aerobic, or ‘with air’, composting to take place and helps drain excess water.
Aerobic composting is faster than anaerobic composting, reduces odour and is better for the environment.
2. Add old compost/soil
The hard work in the composting process is done by bacteria and fungus. A single teaspoon full of soil can contain up to 100 million bacteria and 400 to 800 feet of fungal threads.
By adding in a little bit of old compost or some soil, you will ensure there is plenty of bacteria to kick start the composting process.
3. Use a hot water bottle to kick start your compost
This is a tip I picked up when I received my Hot Bin compost bin. It came with a hot water bottle. After adding a sack of stockpiled compost material, I filled the bottle up with steaming hot water and dug it into the top of the compost.
Nothing happened the first day. After adding a second sack of material I repeated the process the next day. By the third day the compost was hot, reaching 50 degrees celsius.
4. Use a compost duvet
Hot water bottles add warmth, compost duvets maintain warmth, helping to keep the optimum temperature for bacteria and fungi to break down organic materials.
Some compost bins, such as the Green Johanna and its winter jacket, have specially made compost duvets. Alternatively you can buy compost duvets or make your own with materials such as old carpet or bubble wrap.
5. Turn your compost
You can also turn your compost to introduce more oxygen into the mix.
Some systems recommend turning your compost heap every day or two (see the Berkeley method below), but even turning it once or twice will help speed up the composting process.
Learn more: How often should you turn your compost?
6. Create Free Air Space in your compost
Older composting guides rarely mention Free Air Space (FAS) in composting. But FAS gets plenty of attention in professional guides and by compost researchers. While it may not be well known, composting systems which utilise FAS are very effective.
All you need to do is introduce materials which create air pockets in the compost. The highly effective Hot Bin compost bin uses semi-decomposed wood chips to generate FAS which enables air to flow through your compost.
7. Adding nitrogen rich materials
If your pile is slow, the carbon:nitrogen ratio might be out. The microorganisms in compost need both nitrogen and carbon to work. If there is too much carbon, the process will slow down.
To speed up the process try adding ‘greens’ – items which are high in nitrogen, such as grass clippings or manure.
8. Getting the moisture ratio right
Research by Tiqua et al show that when moisture levels are too high, the heat of the compost heap drops and slowed down the composting process. Indeed, another study found that lowering moisture content from 66% to 61% increased the temperature of a compost pile from 55℃ to over 75℃.
One reason for this is that if your compost is too wet, water can fill up the free air spaces. This reduces the oxygen available to microorganisms and slows down the composting process.
If you don’t have the tools to measure moisture levels, simply take a handful of compost and squeeze it. It should have roughly the consistency of a squeezed out sponge.
If it’s wetter than that, simply add a dry material such as shredded paper or torn up cardboard to soak up the excess moisture. It’s also worth considering covering your compost to keep it protected from rain.
Compost can get too dry too. When I turned my large compost heap last summer, the centre was dry despite recent downpours. As I turned it, I sprayed each new layer with water to increase the moisture level.
Do be careful if your compost heap is dry and musty. Musty compost heaps can release harmful bacteria when turned – another reason for ensuring the moisture content in your heap is correct!
9. Compost activators
There are many compost activators available. I personally don’t use them, because there are a number of materials I add to the compost heap which always seem to speed up the process.
I’ve personally found chicken manure to be brilliant. Not everyone has access to this, but you can also use other high nitrogen sources such as nettles and urine to help get your compost heap going again.
What I do use is a compost thermometer. I find this useful (and fun) because it allow me to measure the effectiveness of adding different materials.
Of course, there are many different factors that go into how hot a compost heap gets. But over time, as you add materials and measure the temperature, you start to get an idea of what works best.
10. Add easily digestible materials
Some materials compost more easily than others. Materials such as wood and leaves are high in lignin, which is difficult to compost, especially when this material is large in size.
Other materials, such as grass clippings and shredded paper, compost a lot faster.
11. Reduce material size
The larger the compost material, the less surface area there is for bacteria to work on. By reducing the size of the compost ingredients, you can speed up the composting process.
If you have a bucket of compost ingredients, consider roughly chopping it up with a pair of garden shears. For larger amounts of material, you can use a lawn mower to chop up material, while a compost shredder can work wonders with woody material.
12. Increase the volume of your pile
Large compost heaps work better than smaller ones. With a small pile, the environment outside the pile can cool the contents down quickly. So if you’re using a compost heap rather than a bin, increasing the size of your compost heap will speed up the process.
A pile of at least 36” x 36” x 36” works well. Pallet bins also work well for this, as they have the right size for generating heat.
13. Use the Berkeley method
If you have a larger amount of material available you might want to consider the Berkeley method, designed by Robert D. Raabe of the University of California.
This method involves building up a large compost pile of small materials (1/2 to 1-1/2 inches in size) and mixing roughly equal amounts of greens and browns. The compost is then turned every 1-2 days.
The results? Compost in 14-21 days.
(As mentioned before, I wouldn’t use fresh compost – I find it best to leave to mature before using. When I have used fresh compost from a municipal dump, the results were pretty poor. The same compost a few months later performed brilliantly.)
14. Insulated bins
Of course, most gardeners don’t have large amounts of material waiting ready to be composted. However, insulated bins such as the Hot Bin enable you to achieve rapid composting (30 to 90 days) with smaller amounts of compost material.
15. Add Biochar to your compost
Do note that the Biochar is controversial when it comes to soil amendment, and the Royal Horticultural Society advising only using FSC certified Biochar which is made from European hardwoods.
16. Add worms to finish off the process
Compost cooling down? Hot compost is too hot for worms, but as it cools down worms will move in, further improving the quality of the process. You can always speed up this process by adding plenty of compost worms at an early stage.
Compost worms (Red Wrigglers) can eat their own weight in decaying material in a single day, pushing it through a gut which contains 1000 times more microbial life than the food it consumes.
Worms also help remove pathogens from compost. While worms won’t, unfortunately, produce overnight results, the longer they have to work on your compost the better it will be.
It took me a while (okay, years!) before I got my first hot compost heap, so don’t be discouraged if it takes you a while too.
Remember, composting is an art as much as a science, and one of the best ways to learn is to experiment.