For the organic gardener the basis of good soil structure and plant nutrition is compost. Garden composting allows you to reuse organic waste from your kitchen and garden, thereby reducing the amount of material going to landfill, while producing something useful to help your garden grow healthier.
Compost can be made simply by piling up a heap of organic material, so you don’t really even need a container, but most people prefer to have some way of enclosing the heap and you’ll get better and faster results if you use a compost bin.
The compost bin
The easiest option is to buy a compost bin. These are generally made of wood or recycled plastic. Compost bins may be available at a subsidised price from your local council – check out your area in this postcode search – or you can buy them from garden centres, or online from specialist sites or from Amazon. It’s generally better to buy two small bins rather than a single large one as you can then be filling one while the other is composting down.
Another option is to make your own compost bin. For a very simple version you need four 1.2 metre (4 foot) fence posts, wire netting, nails, and some galvanised hooks and eyes. Clear an area of about one metre square and flatten down the soil. Hammer in a fence post at each corner. Then tack wire netting to the posts. Use the hooks and eyes to attach the netting at the front so it’s easily opened.
Gardeners World have instructions for building a DIY compost bin from old pallets here.
Garden Organic has plans for a moveable stacking wooden compost bin here.
Or you can improvise and use a container such as a builders’ merchants’ bulk bag, or build an enclosure with straw bales.
Trench composting can be used on a site where you are going to plant crops like runner beans, peas, courgettes or pumpkins. The trench is dug in autumn, filled with alternate layers of kitchen waste, garden waste such as brassica trimmings and windfall apples, and soil. It’s then covered with more soil, and left over the winter. The ground is then ready to plant in the spring. This is a good way to use bokashi fermented kitchen waste.
A Bokashi system is used to pre-treat cooked or uncooked kitchen waste including meat, fish and dairy products so they can be safely used as compost without attracting flies or vermin. It’s a fermentation process using bran inoculated with mix of micro-organisms which is sprinkled over the food waste. This is put into an airtight bucket and left in a warm place for about 2 to 3 weeks. The fermented material is then safe to add to a normal compost bin or worm bin, or to dig straight into the ground, where it will break down into compost very quickly.
This is a really good system to use alongside normal garden compost and has the added bonus of producing excellent liquid plant food during the fermentation. The video below shows just how quickly the waste breaks down into the soil, in this case in only 4 weeks. See our posts on bokashi for more information on this system.
Filling the compost bin
Begin with a drainage layer of coarse materials such as straw or twigs about 10cm deep. Then put in about a 15cm layer of garden waste, and continue building up layers of different materials. It’s good to put a little manure or soil between each layer, and fork through the mix now and then to aerate it.
To keep the mix in balance you will need to add very roughly half ‘browns’ and half ‘greens’. Browns are carbon-rich ingredients such as crumpled corrugated cardboard, egg boxes, toilet roll tubes, tough stems, crumpled paper, straw or sawdust which are slow to decay. They maintain air pockets and add structure to the finished compost. Greens are nitrogen-rich materials such as grass mowings, manure, soft weeds and uncooked kitchen waste which are quick to rot but don’t give the compost much body. Most compostable waste is somewhere between green and brown.
The composting process
Composting activity depends on the outside temperature. It will slow down in cold weather and stop almost completely when very cold. Decomposition is much quicker in the summer especially if the bin is in the sun. Insulated thermal composting bins are available which will work all year round.
Using an aerator tool regularly, or ‘turning’ the compost – removing it from the bin, remixing it, and putting it back – will speed up the process. Some compost tumblers can produce compost in weeks by turning the mix without having to remove it from the bin. They are designed for batch composting and need to be filled completely in one go
Water is a vital ingredient in the compost mix. Use a cover to help manage the water content and also keep the heat in. If too dry, very little composting will take place. If too wet the micro-organisms will drown and the bin will start to smell bad and turn slimy. Green materials tend to contain a lot of water, and brown ingredients generally very little, so adjusting the mix helps to manage moisture levels. Add more greens or some water if it seems too dry or some extra browns if it seems wet. The compost should feel damp but shouldn’t ooze water when squeezed in the hand.
Air is another vital ingredient. The organisms needed to make good compost depend on air to survive. If the heap is too wet there is very little air. These aerobic organisms are lost and replaced by anaerobic bacteria which turn the waste to a slimy mass. If this has happened, all is not lost! Holes can be made with a broom handle or an aerating tool right down through the bin to help it drain, or if it’s really wet, the compost can be emptied out, mixed with more ‘browns’ and returned to the bin.
When the bin is full, cover it over and leave for a few months to rot down, then open it up and turn the compost, cover again and leave for another two or three months until brown, crumbly and sweet-smelling.
What to compost
- Uncooked kitchen waste such as vegetable and fruit peelings, tea bags and leaves, coffee grounds, egg shells;
- Grass mowings;
- Annual weeds and the tops of perennial weeds;
- Soft green prunings;
- Dead leaves;
- Shredded paper and cardboard;
- Pet bedding;
- Sawdust and wood shavings;
- Wood ash (in small amounts only);
- Poultry, horse and cows manure;
- Hedge clippings.
Do not compost
- Woody prunings;
- Roots of perennial weeds;
- Diseased plants or seedheads;
- Coal ash;
- Dog and cat waste;
- Disposable nappies;
- Meat, fish or any cooked food (unless first bokashi fermented)
There are two videos by the Henry Doubleday Research Association which are well worth watching:
Garden Organic Video Guide to Composting Part One which includes where to put your compost bin, what can and can’t be composted, filling the bin, compost activators and getting the right mix.
Garden Organic Video Guide to Composting Part Two which covers how to tell when your compost is ready and how to use the compost.