What is Composting?
Composting is a process that transforms organic matter into a dark rich and crumbly material called humus. It is a natural recycling process that occurs in nature, and we can replicate in our own gardens.
Compost adds microbial life to the soil. It improves plant growth, increases the soil’s capacity to hold nutrients and the ability of plants to resist disease. Good soil means resilient plants.
By composting we also reduce our dependency on artificial fertilisers by returning organic matter to the soil.
This also helps to ‘close the loop’. By using our organic waste on-site at home, less waste is transported to landfill (where it would create methane gas, a greenhouse gas, as it degrades).
By creating natural fertiliser with our own composted waste we bring less external materials into our garden. This increases our self-sufficiency whilst reducing the need to manufacture external, artificial fertilisers, or transport soil and fertilisers from one place to another.
Some benefits of composting:
- conditions the soil, improving its structure and moisture retention
- fertilises, encouraging root growth
- mulches and smothers small invasive plants in the garden bed
- prevents the surface soil from drying out
- can be used as potting mix
- reduces outgoing waste
What can be Composted?
On average, around 50% of domestic garbage is compostable.
Organic garbage (fruit and vegetables) will decompose, though not all will decompose fully from composting.
Print this handy list out and keep it near your kitchen compost bin (right-click and save).
CHOOSE YOUR KITCHEN BIN
My personal favourite compost bin is the 3.8Litre Oggi Bin in Stainless Steel. The Oggi is a counter top composting pail with charcoal odour filter. Made from hard-wearing stainless steel, this vintage style trash can makes composting a breeze. Fill and store food scraps, egg shells, etc. odour-free; then transer to your composting unit when full. 3.8L – though I actually keep mine under the sink.
STARTING YOUR COMPOST
For composting to work, both air and water are needed.
It is best to keep the compost heap moist but not drenched to aid in maintaining the right balance of air and water. This encourages the perfect habitat for microbial organisms to do their work of breaking down the material.
Temperature is important as well. Generally speaking the warmer the pile, the faster the decomposition, though too hot (like a black bin in the sun) and the pile will dry out and become inhospitable to microbes.
As long as the balance is maintained, the more green, nitrogen-rich material added, the hotter it grows. In ideal conditions, decomposition can take between eight and ten weeks. Though, in my experience, this is rare in domestic settings.
Size matters – the optimal size is a maximum of one cubic metre of material.
Composting may be carried out with open heaps (covered by a tarp, or hessian) but enclosures or bins are better. They offer protection from pests and keep the pile tidy and sheltered from the weather. If vermin are an issue, a mesh may be needed at the bottom of the bin to prevent burrowing in.
There are two ways to begin.
The first one is simpler and easier to set up but slower to get results. It can be helpful to start with some soil to mix material with. Using this method, the compost can turn to humus in around six months.
For those with more time and a desire to achieve results more quickly, the heap can be built in layers to accelerate the decomposition process. One layer of organic and garden waste of about 150mm is covered with a thin layer of lime and fertilizer (or pre-composted matter), then another layer of about 50mm of soil – repeated all the way to the top of the bin, which must have air vents.
Once you’ve decided which method is best for you, follow the steps below.
- Collect kitchen organic and garden waste in a bin with a lid in the kitchen – on or under the bench.
- Start building your heap in the bin or enclosure you’ve chosen. This may involve alternating layers of kitchen scraps, soil and lawn clippings or else lumping it all together. It is better to have coarser materials on the bottom layer to help with aeration.
- Keep it fed (topped up with scraps), moist and aerated. Remember the hotter it is the quicker it works. Use a compost turner or pitchfork to turn it if using method one if you need to aerate it.
- When your compost is done use it to enrich your soil, plants and trees. Your compost is ready when it is dark brown, crumbly, and earthy smelling.
Worm farming, or ‘vermiculture’, and composting are similar processes.
Where composting creates humus via a natural decay process, in vermiculture the worms turn the organic matter into castings, a rich and concentrated slurry or thick muddy plant food that can be used in the same manner as compost. Though it is often so rich it needs to be mixed or diluted before use.
Earthworms generally speed up the decomposition of organic matter in a compost heap and the worms themselves, when added to soil, help aerate and improve the soil structure permitting greater water retention.
|1. The compost has a bad odour||Not enough air||Turn it more frequently. Cover with grass clippings or sawdust|
|2. The centre of the pile is dry||Not enough water||Moisten materials while turning the pile but do not saturate|
|3. The compost is damp and warm in the middle but nowhere else||The pile is too small||Collect more materials and mix the old ingredients into a new pile|
|4. The heap is damp and sweet-smelling but will still not heat up||A lack of nitrogen||Mix in nitrogen-rich materials like fresh grass clippings, manure, blood meal, or urea|
How much do you use once the compost is ready?
|Plant/Soil Application||Compost Ratios|
|Top-dressing for vegetables, flowers and shrubs||3-6 cm spread uniformly|
|Ground cover and annual planting beds||10cm mixed into the top 30cm of soil|
|Potting mix||25-30% of the volume|
|Mulch for vegetables, annual and perineal planting beds||6-10cm of course compost|
|Incorporation around shrubs||10cm mixed into the top 30cm of soil|
There’s a lot to love about composting – the benefits as outlined above to reducing waste, reducing methane production in landfills, reducing external (manufactured and transported) inputs to your garden, such as artificial fertilisers, the list goes on. It also is basically good for the soul to get your hands dirty (I have read the evidence on this, and have experienced it myself).
Ask me here.