Louise Midgley unravels the mysterious process of turning waste into nutrient rich compost.
The art of producing dark, friable compost from garden waste can be challenging. Many gardeners go about it the wrong way and pile layer upon layer of grass cuttings and prunings on top of each other, under the illusion it will magically transform into fresh, crumbly compost.
In reality the very opposite is true. The sheer weight compacts the rotting vegetation, starving it of oxygen and slowing down the whole composting process. It takes years before the bottom layer is of any use and gives gardeners a minimum of space to add further rubbish.
Understanding how the process works is key to employing the perfect technique to provide usable material within the year.
Compost heaps need to be filled with a mix of nitrogen and carbon rich material. Soft green vegetation, uncooked vegetable kitchen waste and grass cuttings are all deemed to be rich in nitrogen. They contain a lot of moisture and on their own quickly turn into a wet, pungent mush.
Combine them with paper, egg boxes and shredded woody stems which are all carbon rich. These will help absorb moisture and also ensure there are plenty of air pockets throughout. The composting process is aerobic, meaning it needs oxygen to circulate throughout the decaying material, which in turn sustains the living organs within it.
Bacteria and micro-organisms rapidly multiply as they feed on the heap and this activity releases energy, causing a rise in temperature.
As the air supply gets used up, the decomposition slows down and the temperature falls, which is why turning the heap is so important as it introduces more oxygen to keep the process active.
Garden compost bins come in all shapes and sizes to accommodate the largest to the smallest of outdoor spaces. Some are cleverly disguised as Beehive shaped containers and add a beautiful element to the garden.
In autumn keep leaves out of the compost bin. Collect them in bags or a separate container to make leaf mould, as this is a great soil enhancer or useful mulch.
Compostable leaf sacks will hold thousands of leaves. Holes across their surface allow beneficial worms to enter and air circulate.
Autumn is a good time to empty a compost bin. Spread over borders and beds, the harsh winter frosts will help break it down further.
Keep an old piece of carpet on top of the heap to sustain the temperature. Water only if the mixture gets too dry.
Homemade compost improves the structure of clay soil allowing it to drain more freely. It also adds body and nourishment to sandy light soils making them less free draining.
Used on borders and beds compost helps to suppress weeds, keeps the soil moist during dry conditions and is a good mineral source of nitrates and phosphates to feed plants.
Never use any cooked food, meats or dairy products as these will attract vermin.
Homemade compost saves money as you do not need to buy fertilisers, expensive soil conditioners and mulches.