How to make compost
Making compost from garden and household waste is one of the best things any gardener can do. It’s easy and costs very little in time or effort.
Making compost will help you reduce pollution – cut down that landfill! Your plants will grow healthier and look happier for it. It will save you money on fertilisers too.
What can I compost?
If it can rot, it will compost, but some items are best avoided. Some things, like grass mowings and soft young weeds, rot quickly. They work as ‘activators’ or ‘hotter rotters’, getting the composting started, but on their own will decay to a smelly mess.
Older and tougher plant material is slower to rot but gives body to the finished compost – and usually makes up the bulk of a compost heap. Woody items decay very slowly; they are best chopped or shredded first, where appropriate.
For best results, use a mixture of types of ingredient. The right balance is something you learn by experience.
Hotter rotters (activators) – comfrey leaves, young weeds, grass cuttings, chicken manure, pigeon manure
Slow cookers (very slow to rot) – autumn leaves, tough hedge clippings, woody prunings, sawdust, wood shavings
A balanced diet – fruit and vegetable scraps, tea bags, coffee grounds, old flowers, bedding plants, old straw & hay, vegetable plant remains, strawy manures, young hedge clippings, soft prunings, perennial weeds, gerbil, hamster & rabbit bedding
Other compostable items – wood ash, cardboard, paper towels & bags, cardboard tubes, egg boxes
Best avoided – meat, fish, newspaper, cooked food
Do NOT compost – coal & coke ash, cat litter, dog faeces, disposable nappies, glossy magazines
How do I make my compost?
You can make compost simply by adding compostable items to a compost heap when you feel like it. It will all rot eventually but may take a long time, may not produce a very pleasant end product, and could smell. With a little extra attention – taking the ‘COOL HEAP’ route outlined here – you could improve things dramatically. If you want to produce more compost in a short time, and are able to put more effort into it, follow the ‘HOT HEAP’ route.
The cool heap route
- Collect together a batch of compost materials. Try, if possible, to get enough to make a layer of at least 30cm or more in the compost bin. Weed the garden, mow the lawn, empty the kitchen bucket! Aim for a mix of soft and tough items. It may help if you place a few woody plant stems or small twigs on the bottom first, especially if using a plastic bin, as this will improve the air circulation and drainage.
- Start filling the bin. Spread the ingredients out to the edges and firm down gently. Alternate soft and tough items, or mix them together first. Unless items are already wet, water well every 30-60cm.
- Continue to fill the container. Items can be added individually, but a bigger batch is preferable. If most of what you compost is kitchen waste, mix it with egg boxes, kitchen paper, loo roll middles and similar paper products to create a better balance.
- When the container is full – which it may never be as the contents will sink as it composts – or when you decide to, stop adding any more. Then either just leave it to finish composting or go to Step 5
- Remove the container, or everything from the container. If the lower layers have composted, use this on the garden. Mix everything else together well; add water if it is dry, or dry material if it is soggy. Replace in the bin and leave to mature.
The hot heap route
- Gather enough material to fill your compost container at one go. Bring in manure, scraps from the market, neighbours’ weeds and so on to make up the bulk. Make sure you have a mixture of soft and tough materials.
- Chop up tough items using shears, a sharp spade (lay items out on soil or grass to avoid jarring) or a shredder.
- Mix ingredients together as much as possible before adding to the container. In particular, mix items, such as grass mowings, that tend to settle and exclude air, with more open items that tend to dry out. Fill the container as above, watering as you go.
- Within a few days, the heap is likely to get hot to the touch. When it begins to cool down, or a week or two later, turn the heap. Remove everything from the container or lift the container off and mix it all up, trying to get the outside to the inside. Add water if it is dry, or dry material if it is soggy. Replace in the bin.
- The heap may well heat up again; the new supply of air you have mixed in allows the fast acting aerobic microbes, ie those that need oxygen, to continue with their work. Step 4 can be repeated several more times if you have the energy, but the heating will be less and less. When it no longer heats up again, leave it undisturbed to finish composting.
When is it ready?
Compost can be made in six to eight weeks, or it can take a year or more. In general, the more effort you put in, the quicker you will get compost.
When the ingredients you have put in your container have turned into a dark brown, earthy smelling material, the composting process is complete. It is then best left for a month or two to ‘mature’ before it is used. Don’t worry if you compost is not fine and crumbly. Even if it is lumpy, sticky or stringy, with bits of twig and eggshell still obvious, it is quite usable.
Compost hints & tips
Store some dry leaves to mix with grass mowings and other soft green stuff. Make large quantities into leafmould – stuff wet leaves into black plastic sacks (loosely tied), or a wire mesh container. Use after a year or two. Mow leaves on a lawn to chop and collect them up.
Mix well with tougher items to avoid a slimy mess. Leave on the lawn whenever possible – they will soon disappear and feed the grass; this will not cause ‘thatch’. Can also be mixed into a leafmould heap, or used as a soil mulch.
Persistent diseases, such as white rot and clubroot, are best avoided. A hot heap, turned several times, should deal with everything else.
Diseases that don’t need living plants to survive – grey mould, mildews, wilts – may survive in a slow, cool heap. But heat is not the only factor that will kill diseases – the intense microbial activity will also help to dispose of them.
Some perennial weeds will be killed in a hot heap; avoid really persistent horrors such as celandine, bulbous buttercup, ground elder and bindweed. Don’t burn or dump these weeds – they are rich in plant foods. Mix with grass mowings in a plastic sack. Tie it up and leave for a few months until the weeds are no longer recognisable, then add to the compost heap.
Weed seeds may survive a cool heap, but should be killed in a hot one. If your compost tends to grow weeds, dig it in rather than spreading it on the soil surface.
Chop or shred tough prunings and clippings from evergreen hedges before adding to a mixed compost heap. Compost large quantities separately; even unshredded they will rot eventually. Mix with grass or other activating material; water well. Tread down the heap, then cover. In anything from a few months to years you will have a coarse mulch which can be used on perennial beds.
Strawy horse and cattle manure composts well. Keep a sack on hand to bulk up other ingredients. Manure mixed with wood shavings should be left to rot until the shavings are no longer visible. If it is dry, water well and mix with grass mowings, poultry manure or other activating material. When rotted use as a surface mulch. Wood shavings incorporated into the soil can lock up soil nitrogen, making it unavailable for plants for a year or more.
Small pets, like hamsters, don’t produce many droppings but you can still use their waste as a strawy addition to the compost heap. Guinea pigs are marvellous – they love eating weeds and convert them quickly to prime compost material
Newspaper can be added to a compost heap, but in any quantity it should go for recycling into more paper. Cardboard, paper towels and other paper items can be scrumpled up and composted. They are particularly useful where kitchen scraps make up a high proportion of the compost ingredients. Avoid glossy paper and colour print.
Sawdust and wood shavings
Very slow to decay. Add in small quantities; balance with quick-to-rot activating materials. See also ‘Animal manures’ above. Do not use if treated with wood preservatives.