Learn / Composting methods
Heap composting: how to build a compost heap that works.
A heap is the simplest and most widely used way to make compost. You need no equipment beyond a panga, a fork and some water. This guide takes you from choosing a spot to spreading finished compost on your crops.
What to expect
One 2.5 m by 2 m heap, built as in AVRDC’s farm guide, produces about 200 to 300 kg of compost. Applied in planting holes, that is enough for roughly half a hectare.
When a heap works, and when something else is better
A heap suits you if
- You have some open space, ideally shaded
- You have a mix of crop residues, manure and green material
- You want a cheap method with no special equipment
- You can turn the heap a few times over a few months
Consider another method if
- You have very little space, so try a bin or barrel
- You only have wet kitchen waste, so try bokashi
- You are producing large volumes, so see windrows
- Your area is very dry, so try a pit
Choose your site and gather your materials
The site
Pick level ground in the shade, so the heap doesn’t dry out. Keep it close to your manure and water source, but away from streams, rivers and other water bodies. Avoid slopes and waterlogged spots.
Tools
Panga or knife for chopping, fork for turning, bucket or watering can, a dry pointed stick, and something to cover the heap, such as grass, old sacks, banana leaves or a layer of soil.
The materials
Dry: maize stalks, bean stover, dry grass, dry leaves.
Green: fresh grass cuttings, fresh twigs and leaves from hedges (such as lantana or tithonia), kitchen and vegetable waste, weeds without seeds.
Manure: cattle or poultry manure. If you have none, use extra green material instead.
Optional: a handful of wood ash or biochar per layer, and a thin layer of soil.
A Kenyan recipe. The FiBL leaflet for Kenyan smallholders suggests 4 parts manure, 2 parts dry matter and 1 part green matter, by volume. Manure alone will still make usable compost. If you have little manure, use the browns-to-greens rule from What is compost?.
Keep out
Dog, cat and donkey manure, eucalyptus and cassia leaves, plastic and other non-biodegradable items, and medicines. Also avoid industrial waste that could contain metals. Chop everything to about 5 to 30 cm. Smaller pieces break down faster.
SOURCES: FIBL SYSTEMS COMPARISON KENYA, COMPOSTING LEAFLET; FAO HOME GARDEN TECHNOLOGY LEAFLET 6; AVRDC COMPOST MANUAL
Step by step
- Mark the baseMark out the corners with sticks. A base about 2.5 m long and 2 m wide is a good farm size, but keep any heap no wider or higher than about 1 to 1.5 m for the best air flow. Leave a similar space beside it to turn the heap into.
- Lay a coarse baseSpread twigs, straw or other coarse material to let air in from below, then moisten it.
- Add a dry layerSpread chopped dry material about 15 cm deep and wet it thoroughly.
- Add a manure layerSpread manure over it. Make it thin (about 2 cm) if manure is scarce, or up to about 15 cm if you have plenty. Moisten it.
- Add a green layerAdd fresh green material, then sprinkle a handful of wood ash or biochar, and a thin layer of soil. Too much wood ash is a common mistake.
- Repeat, up to five layersDivide your materials into at least three portions and repeat the layers. Build longer, not taller.
- Soak itWater until the heap is as damp as a wrung-out sponge, with no water running out. Aim for roughly 45 to 65% moisture.
- Add air channels and a thermostickPush bunches of dry grass or bamboo poles vertically into the heap about 1 m apart. Push in a dry, pointed stick diagonally to the middle so you can check the temperature.
- Cover itCover with soil (about 10 cm), grass, old sacks or banana leaves. This keeps in moisture and heat, and keeps rain out.
Checking, turning and watering
A heap needs little attention, but the attention it needs matters. The sources agree on the method and differ on how often to turn, so here are two approaches.
| Approach | Turning | Ready in |
|---|---|---|
| Hands-on FIBL KENYA LEAFLET | Every 5 days for the first 3 weeks, then weekly to 2 months. Check the stick every 3 days at first. | About 2 months |
| Low-effort FAO; AVRDC | First turn at about 15 days to a month, when the heat drops. Then every few weeks, up to about every 2 weeks, until dark. | 3 to 4 months |
Using the thermostick
- Hot to the touch means the heap is working. A well-built heap can reach 60 to 80°C, and heat fades after about two weeks.
- Cool means it is not active. Check moisture and mix, and turn the heap.
- A whitish coating on the stick means it is time to turn the heap and add water.
How to turn it.
Fork the material into a new heap beside it, moving the top and outside material into the middle and the bottom to the top. Water any dry material as you go. Turn promptly if the heap gets too hot (above about 63°C) to bring the temperature down, and stop turning when it no longer heats up after a turn. Then let it cure for at least a month.
SOURCES: FIBL KENYA LEAFLET; FAO HOME GARDEN LEAFLET 6; AVRDC; UNIVERSITY OF NEBRASKA–LINCOLN EXTENSION (G1315)
Knowing it is ready, and using it
Ready
- Dark brown or greyish, crumbly, almost granular
- An earthy, forest-soil smell
- Near air temperature
- No recognisable plant material (sieve out coarse bits and return them to a new heap)
Not ready
- A foul smell
- Visible plant material
- Still hot, or heat spikes after turning
Immature compost can scorch plants and reduce the nitrogen they can reach.
Using it
| Where | How |
|---|---|
| Maize and row crops | A handful in each planting hole, applied just before planting. |
| Home garden beds | Spread and mix into the upper topsoil. Don’t use more than about one-third of the tilled depth. |
| Shrubs and trees | Mix into the planting soil: at least 10% by volume, about 30% is best and no more than 50%. |
| Dry season | About one large sack per 10 m². You may need a second sack at the start of the dry season. |
Poor soils need more compost than fertile ones. Protect stored compost from sun and rain: keep it in the shade or cover it with about 10 cm of topsoil.
SOURCES: FIBL KENYA LEAFLET; FAO HOME GARDEN LEAFLET 6; AVRDC COMPOST MANUAL
Common heap problems
| Problem | Likely cause | Fix |
|---|---|---|
| Slow to decompose | Too wet, too dry, too small or too large, or too little manure or green material. | Check moisture, turn it, and add nitrogen-rich material. |
| Never heats | Too dry, or too much dry carbon-rich material. | Add water and green material or manure, and re-stack it. |
| Smells rotten | Waterlogged and short of air. | Turn it, mix in dry material, and cover it from heavy rain. |
| Catches fire (rare) | Too dry and very large. | Keep it damp, and build several smaller heaps instead of one large one. |
Mistakes to avoid
Stacking more than five layers, using banned materials, building on a slope, in full sun or near water, overusing wood ash, skipping turning and checking, and using the compost before it is mature.
Questions people ask
Do I need manure?
Not strictly. Manure speeds things up and adds nitrogen, but you can use extra green material instead. Heaps made only of dry material and no green or manure tend to stall.
Can I add kitchen waste?
Yes. Vegetable and fruit waste works well. Keep meat, bones and cooked or oily food out, and bury scraps in the middle of the heap so they don’t attract flies or rats.
What about the rainy season?
Cover the heap to keep it from getting waterlogged, add more dry material, and make sure water can drain away from the base.
Why did my heap shrink so much?
That is normal. Decomposition reduces the volume a lot, so you end up with much less compost than the pile you started with.
Can I add a starter or EM?
You can, and the FiBL leaflet lists commercial inoculants as optional. Most heaps work without them, so get the mix, moisture and air right first.
Want to see it done in person?
We train groups, households and institutions to build and manage compost heaps with their own materials.