Advice
Help & Advice
Home composting
Good garden management generates a lot of waste plant material. Home composting is the most environmentally-friendly way of dealing with this material and produces a material that is superb as a mulch and soil improver.
Putting garden waste in the dustbin is environmentally damaging as much of the material will simply end up in landfill. Many local councils operate green waste collection schemes whereby they actually collect the green waste separately and compost it. If you take green waste to the local civic amenity site most councils will then compost it. Some councils actually give the composted material back to their community, some will sell it back and others use it in landscaping schemes. Other councils provide compost bins at a subsidised cost to encourage home composting. Unfortunately council policy varies dramatically countrywide.
Composting kitchen and garden waste will produce a free, environmentally friendly source of organic matter which can be used throughout the garden. Composting is simply a biochemical process whereby organic matter is decomposed by naturally occurring micro-organisms.
The site and container
An earth base under a heap allows drainage and access to soil
organisms. An open heap of organic matter piled into a corner
of the garden will decompose slowly and produce compost eventually.
A bin will help insulate the heap, prevent the organic matter
being blown around the garden and accelerate the process of
decomposition. There is a wide range of containers available
all of which will help produce compost. Better quality compost
is usually produced more quickly from larger initial volumes
of waste. A good size to aim for is 1 cubic m (1.3 cubic yd).
What to compost
The most important aspect of composting is the raw materials. Aim for between 25% and 50% soft green nitrogen-rich materials
(e.g. grass clippings, annual weeds, vegetable kitchen waste,
or manure). The remainder is made up of woody 'brown' carbon-rich
material (e.g. prunings, wood chippings, paper, cardboard,
straw or dead leaves).
Most materials of organic origin will decompose eventually, including citrus, rhubarb and the clippings of conifer, ivy, walnut, laurel and yew. Woody material will decompose more quickly if it is shredded first. Importantly remember not to let any one material dominate the heap - especially grass clippings.
Avoid diseased plants, perennial weeds, weeds and mowings where weedkillers have been used, weed seed heads, meat, fish and cooked foodscraps and cat or dog waste.
Compost can be turned periodically to introduce air (aerobic composting). Household waste tends to be added in small amounts and easily becomes compacted. Aerobic compost breaks down quickly and generates warmth killing some weeds, seeds and diseases. Without air the process is slower, cool and termed anaerobic. The end result is usable, but aerobic compost is preferred.
Material to compost
Grass clippings, annual weeds
Prunings and hedge trimmings
Leaves
Fruit and veg, kitchen waste
Paper and card
Selected pet waste/bedding
Soft, moist, nutrient-rich
(high-nitrogen) material;
decays rapidly.
Carbon-rich, relatively
low-nutrient material;
slow to decay.
Carbon-rich, low-nutrient
material; decays slowly.
Soft, moist material, relatively nutrient-rich; decays rapidly.
Dry, carbon-rich, low-nutrient, highly absorbent material;
decays slowly.
Nutrient content variable; quite rapid decay, depending whether wood shavings or straw is used
Note: use only herbivore waste.
Add in small batches, incorporate with the existing materials or mix with equal quantities of woody material or shredded paper.
Chop or shred and mix with nitrogen-rich materials before composting for eight to 12 months.
Shred and mix with nitrogen-rich waste, or stack separately and keep moist to produce leafmould.
Chop up and add to balance drier, carbon-rich waste.
Shred or ‘ball-up’ before mixing with moist, nitrogen-rich material.
Mix well with other material: add any with a high proportion of animal waste to woody waste; drier waste is best with soft, nitrogen-rich material.
Turning the compost heap
The composting process is aerobic: it requires air. If the heap is too wet or compacted, oxygen levels drop, leading to anaerobic (without air) decomposition - a slower, less-efficient process.
Ideally, organic matter should be formed into a heap all in one go, and turned periodically to introduce air. In practice, most gardeners accumulate waste gradually and build up layers that tend to compact. Turning the compost is laborious but beneficial as it aerates the material, speeding the process: failure to turn the heap is probably the main cause of poor results. It is also important to keep the heap moist in dry weather.
Accelerators
Activators are materials intended to balance carbon and nitrogen within a heap.
If the nitrogen (green) to carbon (brown) balance of your heap is not right the bacteria and micro-organisms who produce the compost will work much more slowly. If your heap is predominantly brown material then purchasing a high nitrogen activator may be of benefit or alternatively fresh manure could be used; use manure at one bucket for every 15cm (6in) layer of compost, or 270g (9oz) of organic fertiliser or 140g (5oz) of sulphate of ammonia.
If the heap is predominantly green material, add high-carbon waste such as chopped woody material, shredded woodchip, straw or paper.
Most commercial activators are high nitrogen, but you can also purchase high-carbon activators; these are usually aimed at composting grass.
When is it ready?
Garden compost can take between six months and two years to reach
maturity. Mature compost will be dark brown, with a crumbly
soil-like texture and a smell resembling damp woodland. It
is unlikely that all the material in the heap will be like
this. In an unturned heap the top is usually dry and undecomposed,
the base will be wet and have a bad odour while the 'core'
of the heap may be mature compost. Separate these portions
so they can be re-composted and use the mature core.
Find out how to make leafmould from tree leaves
Home composting leaflet
To view this document you will need a copy of Adobe Acrobat Reader. We strongly recommend that you download the latest version to prevent problems viewing the documents. This is available free from the Adobe website. Click on the logo to go to the website.