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Make your own compost

Fraser Sherrard by email, 2 July 2018:

‘At 67 years old I tried the no dig approach, spreading my own compost made last summer. Using row cover (fleece) here in Zone 5b, New Brunswick in Canada, we were eating salad in mid to late May, well before our normal planting time. The sheer abundance of produce, reduction in pests, and health of the plants is amazing; I am working less and enjoying more, thank you.’

Making compost is a fascinating hobby, and if you have never tried it do have a go. You will convert wastes into value, perhaps enjoying the process as much as the result.

Compost varies enormously, and homemade compost is the most variable and interesting. Every batch is different, thanks to seasonally-changing ingredients and conditions. An added bonus is the range of local microbes in homemade compost, fantastic for human as well as garden health.

8. Charles adding material to his heap after trimming vegetables
Adding material to the compost heap, after trimming vegetables
1a. Profile of a compost heap where the bottom layer is 22 days old
The profile of a compost heap, where the bottom layer is 22 days old
1. A barrow-load of ripe compost, forked not sieved and 8-12 months old
A barrow-load of ripe compost, forked not sieved, and 8–12 months old

Why make compost?

Wouldn’t it be easier simply to lay undecomposed matter on the surface? This is called chop and drop, and in dry climates it may be the best course to take.

However, in damp climates undecomposed waste on the surface results in slugs. And decomposition is quicker in heaps, which are more than just ‘decaying material’. Well made heaps convert waste matter quickly and tidily into stable organic matter, or humus.

This is the Wikipedia definition of humus:

‘Fully humified humus has a uniformly dark, spongy, and jelly-like appearance. It has no determinate shape, structure, or quality. However, when examined under a microscope, humus may reveal tiny plant, animal, or microbial remains that have been mechanically, but not chemically, degraded. This suggests an ambiguous boundary between humus and soil organic matter. While distinct, humus is an integral part of soil organic matter.’

Albert Howard, who pioneered new ways of compost making in 1920s India, found that heaps could contain more nutrients than were in the materials added.

Defining compost

Compost is organic matter that has decomposed, including leaves, manure, weeds, kitchen scraps, ash, wood and paper. Compost provides food for soil organisms in a slow and steady manner. Their excretions feed plants, and their activity helps to aerate soil and create structure, such as aggregates of crumbs.

14. Charles lifting the side of a compost heap
Lifting the side of a compost heap
15. Beside the heap which is 3 months old since the first additions, 2 months since the last ones
It has been three months since the first additions were added to this heap, and two months since the last

Compost holds nutrients in a stable, soil-enhancing form. Using it as mulch results in healthier plant growth plus better soil quality. A compost heap speeds up nature’s process of decomposition, and allows us to add other wastes to our own.

So what is compost tea?

This term is used to describe two completely different liquids: aerated and anaerobic tea. In gardens you don’t need to use either, though you may choose to. Aerated tea makes sense on farms where there isn’t enough compost for mulching, and also on golf courses, because you can’t lay compost on the greens.

1. Aerated compost tea is made with small amounts of the highest quality compost, aerated for at least 24 hours by an aquarium air pump. Add sugar such as molasses, to feed and help multiply the bacteria and fungi. This tea is all about stimulating soil microbiology; it is not a nutrient feed, but it helps nutrients to become available.

Aerated compost tea gives great results for such a small input of material. You need the kit and time to set it up and run it, then to apply it. However, in a garden with mulches of composted and decomposing materials, I see little benefit from using it, in proportion to the time needed.

2. Anaerobic compost tea is smelly, made by soaking compost in water, and is a weak feed of nutrients. I have used this a few times over the years and have been unimpressed by the difference it has made, in proportion to the time needed and the unpleasant odours. It’s simpler to mulch with compost, or comfrey leaves for that matter, and let nature do the work.

Organic matter

Organic matter is food for soil’s billions of mostly unseen inhabitants. They aggregate soil into crumbs, resulting in structure, drainage and aeration.

  • Organic matter is carbon based – more in the soil means less in the atmosphere.

Fresh manure is also organic matter. However, compared to compost, it contains fewer living organisms and its nutrients are more water-soluble. Hence the worries over nitrate leaching from slurry, worries which confusingly and wrongly have become associated with compost.

The nutrients in compost are generally insoluble in water, and do not leach into rainfall. At the same time, compost is about way more than fertiliser and feeding plants. Its biology is more important than its chemistry. Don’t worry about compost’s ‘low’ NPK figures, compared to when you may have used synthetic fertilisers. Compost and no dig serve to unlock food in soil which was previously unavailable.

Compost process

Decomposition happens within a spectrum of possible ways. Garden heaps have a mixture of processes enabling decomposition:

  • Bacteria are at one end of the spectrum – heat builds from their proliferation, and the rapid decomposition of organic matter which they bring about.
  • Fungi are at the other end – breakdown happens at lower temperatures and more slowly (through mycelial activity), in piles of leaves and woody materials for example.

One stage of maturity is when a heap’s warmth has mostly gone, because the bacterial processing is finished. Then fungi multiply, especially in heaps with woody materials.

Often brandling or tiger worms arrive when heat reduces, and heaps effectively become wormeries for a while. They reduce in quantity and increase in quality.  At Homeacres it takes three to six months before worms appear in my heaps. Before that it is too warm for them, except in winter months.

16. Using a manure fork to turn the 2-3 month old compost
Using a manure fork to turn the two to three-month-old compost
17. How it looked after being turned, aerated and the lumps mixed while turning
How it looked after being turned and aerated, with the lumps being mixed while turning
18. How compost can develop: this is 4 months after a heap was turned, and has had black polythene on top to keep it moist
How compost can develop – this is four months after a heap was turned; it has had black polythene on top to keep it moist

Contrast this with green waste or municipal compost, which looks fine and ‘finished’ after just a few weeks, from being shredded and then turned regularly. However its blackness is from carbonisation caused by high temperatures, up to 80°C (176°F). This is a result of thermophilic bacteria being encouraged by the regular turning and introduction of air.

I take deliveries of such compost in this so called ‘ready-to-use’ state, and measure temperatures of 60°C (140°F) at the time of delivery, even though the appearance is black and crumbly. I have tried spreading this compost and then planting through it. The resulting growth was poor, compared to when I spread it after four to six months of extra fermentation. Lesson 16 compares and explains the qualities of several different composts.

Moisture levels

In climates where the air itself is often damp, as are the materials that you are adding to a heap, watering is rarely necessary. As damp materials decompose, their moisture is free to seep into the heap.

Check your compost’s moisture by squeezing a handful to see how much comes out. A rule of thumb is that more than two droplets of water suggest soggy compost, which therefore needs more air.

If there is enough brown matter in a heap, excess moisture can either drain out or be absorbed by drier materials. Too little brown results in compost becoming soggy and airless, called anaerobic. This slows or halts the process of breakdown. A remedy would be to turn the heap and add paper, soil and other brown ingredients.

12. Shredding stems of broccoli which are half green and half brown
Shredding stems of broccoli, which are half green and half brown
13. What they look like after shredding
This is how the stems look after shredding

Maintaining correct moisture

Moisture levels are hard to assess when adding materials, but during dry summers you probably need to water. For example 2018 was unusually dry here, and when turning heaps made in the summer we found many dry pockets.

This afforded a chance to water with as fine a rose as possible, otherwise water droplets would have run through and away. Plus, in dry conditions, it’s worth firming materials or even walking on the heap. This reduces air pockets, holds moisture and builds warmth.

Compost ingredients – green and brown

GREEN compost ingredients are soft, leafy, high in nitrogen, usually moist and low in fibre.

  • Kitchen peelings, grass, weeds and food wastes are mostly green. Some green ingredients, such as coffee grounds and horse poo (both 3% nitrogen), look brown.
  • Brown ingredients are fibrous, drier, and more woody than leafy.
  • Some materials are both green and brown, see the broccoli stems in the photos below.

Why differentiate? When you achieve the desired balance of about 50:50, this contributes to having the correct level of moisture, warmth and structure for air. The result is decent aeration and sweet compost.

An excess of green results in high heat, bacterial dominance and a lack of air – making the compost sour and anaerobic, often dark black. A dominance of brown material results in moderate warmth, more fungi and a slower process.

Fresh manure from any animals, especially chickens, is green and so is urine. Both are excellent for speeding decomposition. Should you have large animals, such as a cow or a horse, their manure and bedding would ‘take over’ the compost heap volume-wise, meaning your compost heap would become more of a manure heap.

Beware of adding too much wood-flake bedding, because it’s kiln dried and very slow to decompose. Old manure with a fair balance of poo and bedding becomes great compost, just with different qualities to garden wastes.

BROWN compost includes chipped and shredded materials, which are woody. Their speed of composting depends on size, the type of tree wood, and whether they have been crushed or simply cut – crushed results in more surface area and faster decomposition.

Coniferous wood is better kept for mulching rather than composting because it rots so slowly, thanks to oils in the wood. However, if you are given a pile of chips and it contains, say, a third or less conifer, then that can work for adding to a compost heap when half decomposed and in small pieces. Other brown materials are:

  • Shredded and crumpled paper.
  • Cardboard in medium pieces, say 20 cm (8 in) diameter, and not shiny cardboard or food packaging with hidden polythene.
  • Soil and yard sweepings (only they often contain many weed seeds).
  • Tree leaves.
  • Wood ash up to, say, 5%.
  • Straw, which gives good structure and aeration, and works best when already wet and half rotten.

Summer sees a surplus of green, so I keep a pile of decomposing wood chips near to the compost bays. We add them to any large additions of grass mowings and fresh leaves. They can be anything from six to eighteen months old – I find the older the better. To speed up decomposition, we run a lawnmower over them before adding to heaps.

Good to compost

Weeds (green) often include soil (brown) on their roots, which means you can make fine compost from them alone. Shake off as much soil as possible, to create a chance for heat to be created from a sufficient amount of green.

You can compost perennial weeds too. I add roots and leaves of bindweed, docks, nettles, buttercups, dandelions and couch grass. They break down even in winter’s cooler heaps, and regrow only if left exposed to light. Save time by not separating out perennial weeds and  allow them to add value to your compost.

  • With no dig you apply compost on the surface. This gives the chance to see and remove anything you don’t want in the finished compost, such as an odd root of bindweed.
24. Pasture weeds after four months under a woolen carpet. Only bindweed has survived
Pasture weeds after four months under a woollen carpet – only bindweed has survived
24a. We used trowels to lever out some of the roots and all this went on the compost heap
We used trowels to lever out some of the roots, and all this went on the compost heap

This comment is from Stringfellow, in a forum topic about horsetail, June 2018:

‘I had a lawn of horsetail covering my plot. Being a total beginner back then, and paranoid about horsetail growing through concrete bunkers etc. we mowed the top growth and skipped the lot. Now wish I’d composted it all. Just keep an eye on the heap, you’ll get little if any regrowth – I’ve found they quickly wither and die. It all ends up back on your plot to help grow vegetables.’

Tree leaves start green and older leaves become more brown, so autumn’s tree leaves are mostly ‘brown’ in compost terms. They compost better if chopped by a rotary lawnmower. Large amounts may be better left to decompose slowly into valuable leaf mould – in their own heap, through fungi.

Rhubarb leaves and citrus peel are green, and good to compost.

Eggshells are brown and bring structure to a heap but decompose slowly. After spreading the compost they may sit as a mulch on top, which is fine.

Diseased materials are fine to add

Diseased leaves are good to compost, such as mildewed courgette and lettuce, blighted potato and tomato. Also tubers, and fruits with late blight. Blight (and other fungal spores which cause disease on leaves and stems) need living plant tissue in which to survive, hence they die in a compost heap, and likewise in soil.

  • On two occasions I have spread compost made with blighted leaves around tomatoes in the polytunnel, with no ensuing problems.
  • Because blight spores do not survive in soil, there is no need to empty greenhouses of their soil after blight occurs.
2. Starting a heap, and on soil is fine, better than say concrete
Starting a heap – on soil is fine, and better than concrete, for example
3. Layers of brown and green in a new heap
Layers of brown and green compost in a new heap

Size/length of materials

It is worthwhile to cut and split longer lengths of stems and wood into pieces of 10 cm (4 in) or less. Otherwise they don’t pack down, and only very slowly convert to compost. As much as a heap needs air, it also needs an even density, and this keeps moisture consistent too.

We use a rotary lawnmower to chop stems of broad bean and pea, and a shredder for woody stems including hedge prunings. Softer wastes which are long and thin can be cut with secateurs or a knife.

Temperature – does a heap need to be hot?

In a word, no. Heat is not vital, but it speeds up  the process and kills weed seeds. You can also make excellent compost at temperatures of 30–50°C (86–122°F). To know the temperature, buy a ‘compost thermometer’ like the ones in my photos.

These are some of the differences between compost from cooler and hotter heaps:

  • Temperatures below 55°C (131°F) do not kill weed seeds.
  • Hotter heaps decay more bacterially, especially when temperatures are over about 50°C (122°F).
  • Cooler heaps below about 50°C (122°F) decay in a more fungal manner.
  • Cooler heaps result in browner compost, compared to the black colour of hot heaps.
  • Cooler heaps take longer to decompose.
  • There is a greater range of microbes in cooler heaps.
9. Even in December you can have heat, if there are enough green materials to add
Even in December you can have heat, if there are enough green materials to add
10. This heap was finished two months earlier but still has some warmth!
This heap was finished two months earlier, but still has some warmth!
11. Coffee grounds and cardboard are creating warmth, even in cool weather
Coffee grounds and cardboard are creating warmth, even in cool weather

Choice of bin: solid or open?

A bin with plastic or wooden sides keeps materials together, increases warmth and moisture, and allows you to keep rain out if there is a lid or cover. It’s said that wooden bins need slatted sides to allow entry of air, but this can result in dry edges.

Homeacres’ heaps with solid wooden sides make great compost, the wood conserving both heat and moisture. I screw them onto the shed posts, then it’s simple to unscrew them when turning and emptying heaps.

Or, if you have heaps made from pallets, line the sides with thick cardboard.

Plastic bins are usually smaller, and this restricts the heat they can maintain. My trial with a Rotol ‘dalek’ bin saw temperatures rarely exceed 45°C (113°F), and weed seeds survived the process. Nonetheless it was good compost, and the bin is easy to lift off when you want to use it.

4. Plastic compost bin lifted off after 4 weeks of adding materials in May
The plastic compost bin has been lifted off, after four weeks of adding materials in May
5. A heap made from pallets, with wooden posts at the corners
A heap made from pallets, with wooden posts at the corners
22. A front made of liftable planks is practical for filling and emptying heaps
Using planks of wood at the front, slotted into the frame at each end; new planks are added as the heap rises
23. Open compost bays at Sissinghurst market garden in Kent
Open compost bays at Sissinghurst Market Garden in Kent

Homeacres 7 bays

I am increasingly asked for the plan of my composting system here. However there was no plan, only a series of rough sketches as I firmed up ideas.

Below are the specifications, which will enable you to build something similar. Alter the specifications to fit your site. Seven bays could be three for an allotment or five for a large garden. I fill six at most in a year, sometimes five. The empty bays are useful storage space, and the roof means a dry and ventilated area, on the heaps, to dry onions.

  • The main posts are 6x6in (15cm) pressure treated softwood, and set in 12in/30cm concrete. The posts are 8ft/2.4m long, about 1ft/30cm sawn off the back ones to create the roof slope.
  • All the roof is treated softwood timber, and many sides were half inch/12cm plywood. But now I am moving to planks of Douglas Fir.
  • Everything else is what you see. Steel roof.
  • We dug the holes, builder erected the structure for £3k/$4k.
  • Each bay is 1.7m deep and 1.8m wide, roughly 6 feet square, and the base is soil. So all materials sit on the base of earth.
  • After filling to say 1.5m/5ft high, the materials sink to half that within six to eight weeks.
  • Therefore each bay contains about 2.1 cubic metres/2.7 yards of compost, or 1.5 tonnes depending on moisture content.
  • The first bay we fill is no.2, then turn to right into number 1. Second bay to fill is no. 3, etc.

In 2016 I designed my seven bay system at Homeacres, including a roof to keep rain off the  heaps. I had wanted a roof for years, because too much rain entering heaps can change aerobic composting to anaerobic, by excluding air.

Building a heap

Add your garden waste as it is produced, in level layers rather than as a mound in the middle, in order to have uniform spreads of different materials. Sometimes you need ‘balancing materials’, in terms of green and brown:

  • In the growing season keep a reserve of brown: paper, small wood of any kind, autumn leaves, cardboard, soil and twiggy materials.
  • In winter you need extra green, such as fresh manure, coffee grounds and spent hops.

Richard Loader on Facebook – UK Here We Grow, 13 August 2018:

‘Since visiting Charles Dowding’s garden and seeing his composting system we have started to see our compost heaps very differently. Previously weeding, trimming, mowing seemed like chores but these activities have transformed into harvests of food for what we now call “the beast”. We gather the “browns and greens” and blend them so as to satisfy the appetite of the beast and enjoy monitoring the process of decay and heating with a long probe thermometer. It’s like having a new pet to care for.’

The photos below were all taken on the same day, after I had added several barrowfuls of material to finish a heap which was already four weeks old.

27. Compost making: layer of six month old wood chips and coffee grounds on four week old heap
Compost making – a layer of six-month-old wood chips and coffee grounds, on a four-week-old heap
Next I added a layer of Homeacres soil that came from some building work
29. Old straw and a little fresh horse poo from a neighbour's manure heap
Old straw, and a little fresh horse poo from a neighbour’s manure heap
30. Four full loads from the lawnmower’s grass collector and leaves from the edge of Homeacres
Four full loads from the lawnmower’s grass collector, and leaves from the edge of Homeacres
31. I screwed a new board to the front, now full height
I screwed a new board to the front – it is now at full height
32. My pile of six month old wood chips and a homemade sieve
My pile of six-month-old wood chips, and a homemade sieve
33. On top of the grass I added a layer of half soil, half wood chip
I added a layer of half soil, half wood chip on top of the grass
34. Already the new additions are warmed from below and the 30cm/12in probe reads 66C/131F
Already the new additions are warmed from below, and the 30 cm (12 in) probe reads 66°C/131° F
35. The final addition is a layer of more soil and old wood chip
The final addition is a layer of more soil and old wood chip
36. And finally this is thick cardboard to hold moisture and warmth.
And finally thick cardboard, to hold moisture and warmth
37. Eight weeks later and we are about to turn the heap
Eight weeks later – we are about to turn the heap
38. After the turn: everything you see is 8-12 weeks since being added
After the turn – everything you see was added 8–12 weeks ago

When to stop adding more material

Small gardens generate less material and may struggle to fill a bin, even over a whole year. Use the smallest bin you can because a small, full bin makes better compost than a larger, half-empty one.

After perhaps a year of filling, lift up the bin (it will be light!) and place it close to the now exposed heap. Then you can fork out the top, undecomposed part and put it at the bottom of the empty bin. Finally, help yourself to compost from the bottom part.

  • In large gardens, pallet sized heaps may fill to a height of 1.5 m (5 ft) within perhaps a month.
  • Even at this point, continue filling for another 2–4 weeks, until the heap is hardly sinking any more.
  • Unless you have a roof, cover with straw/carpet/cardboard/woodchip/polythene, while filling a new heap.
  • Optional for a faster finish: turn the heap 1–2 months after the final additions.
6. This compost is 12 days old and has been turned three times already
Trying a different method of assembling a heap in one day – this compost is 12 days old, and has already been turned three times
7. Same heap now 24 days old and no more heat. It was a little too moist
The same heap, now 24 days old – there is no more heat as it was a little too moist

Turning compost: is it necessary?

Turning is worthwhile for larger scale compost makers with several heaps, in order to mix and aerate, and to create a more even compost in a shorter time. For most of us, just one turn of a larger heap makes a worthwhile difference. Two hours of turning is sufficient for a Homeacres heap of about a tonne.

You need an empty space or bin next to the heap you are turning. Use a manure fork with long prongs – good for shaking out dense lumps to introduce air. Turning is about mixing, aerating and checking the quality. If you discover dry portions, add a little water; or conversely, add some dry paper if it’s soggy.

  • For a small heap that perhaps barely fills during a whole year, turning is not worthwhile.
  • A simpler way to ‘turn’ is by occasionally using a proprietary compost aerator, to lift and mix the materials.
  • The law of diminishing returns applies to compost turning. Gains are marginal from a second turn.
20. A summer heap, took 6 weeks and oldest addition is 11 weeks, is still 55C/131F in the middle
A summer heap – this took six weeks, and the oldest addition is 11 weeks; it is still 55°C/131°F in the middle
21. After turning, we found several dry pockets and gave water to correct the moisture level
After turning we found several dry pockets, so added some water to correct the moisture level

Finished compost

Within a year, or perhaps within months in the summer, your compost will have a crumbly texture of variable quality. A dark brown colour is better than black, which suggests a lack of air and too much moisture.

Any large lumps need breaking up with a fork while loading a wheelbarrow. Sieving compost before use is not worth the effort and time needed, unless you want it for propagation. If there are large pieces of undecomposed material, simply pull them out while loading a wheelbarrow, to add to your current heap.

You may find the odd root of perennial weeds, which are white and therefore noticeable. There is nothing to fear from such roots because, even if you miss them while spreading, you will have another chance to remove them later when you notice regrowth. This visibility, and the easy removal, are both advantages of no dig – compost being on the surface rather than incorporated.

19. Compost with worms like this is not 100% “finished” but your soil organisms will love it
Compost with worms like this is not 100% ‘finished’, but your soil organisms will love it
39. I am spreading 8 month old compost, after a harvest of celeriac in December
December – spreading eight-month-old compost, after a harvest of celeriac


I have described the principles of easily composting mixed wastes (the variety that many of us have) without too much effort.

You can also make compost more rapidly, in as little as 14 days. I have tried this a few times, but find it inefficient in terms of the time and energy needed, say three turns. Also I preferred the quality of my slower, once turned heaps.

Another variation is explained in this video of the Johnson-Su bioreactor, which contains only wood ingredients, in a fully aerated and moistened pile. The intention is for there to be fungal rather than bacterial decomposition, and without any turning. I made one of these in spring 2020. I like that it’s low-tech, uncomplicated, and uses common wastes of chipped or shredded wood. It took six hours to make the frame and add a tonne of wood chip.

I cut holes in the pallet, for slotting in drain pipes to create ventilation holes
Adding sides and five pipes to the bio-reactor compost heap
Lifting recently cut wood chip into the bio-reactor
Removing pipes from the bio-reactor – on day four the wood chip is 30°C

Microbial richness is a key asset of good compost, as much as are the nutrients. Lesson 14 now considers definitions of fertility, and the values of compost for soil and plants.


sow & propagate
Transplant - Size, time of year, Spacing, support
container growing
Prune and train plants/thin fruit
Harvest times and method
Potential problems