Composting

How does composting work?

There are two kinds of composting; HOT and COLD.  In both, bacteria and fungi break down organic matter like fruit and vegetable scraps in the compost, producing heat.

In HOT composting, the heat should rise to 65°C.  The rising temperature speeds up the decomposition process, kills off weed seeds and harmful pathogens that could otherwise compromise your compost.

COLD compost can also be made without the high temperature.  This compost should not have weed seeds, as to destroy the seeds and stop them from spreading, they must be put into a HOT compost.

Both methods result in a safe-to-use compost, ideal for nourishing gardens and landscapes.

Getting started with composting

There are four key steps to consider when starting a composting pile, whether hot or cold composting.

1. Choose a compost option that best suits your home

There’s a range of home composting options to suit a variety of homes – from small-space systems to homes with compact courtyards, spacious backyards, or large properties.

If you live in a rented house or a home with limited or no yard space, consider:

• Bokashi bin (also known as a bokashi bucket)
• Worm farm
• Taking your organic waste to someone who is composting or to a community garden which has a compost.

If your home has some garden space or you live on a large property, consider:

• Traditional compost bin
• Compost barrel or tumbler
• Smaller in-ground compost bucket or larger in-ground composting systems
• Compost heaps
• Or any of the options designed for smaller spaces

What to compost:

•  Cooked foods are ok but raw is preferable
• Fruits and veggies
• Eggshells – crushed
• Coffee grounds and loose leaf tea (or remove tea leaves from bags as they are non-organic)
• Cooked grains without meat, like pasta, rice, quinoa, or oats
• Beans, lentils, hummus, bean dips
• Nuts and seeds
• 100% cotton or 100% wool material (any amount of polyester or nylon won’t       compost and will be left over)
• Hair and fur
• Fireplace ashes
• Shredded paper, cardboard, and newspaper
• Leaf clippings and dead houseplants
• Yard waste of all kinds including branches, bark, leaves, flowers, grass clippings, and sawdust

What not to compost:

• cooked food (can get very smelly)
• animal meat – bones attract pests and take longer to break down
• animal products – dairy, cheese, yogurt
• oil and grease
• raw or cooked eggs
• glossy paper
• plastic
• diseased plants
• animal or human faeces

2. Choose a suitable location

Choose a composting method that best suits you; find a flat, well-drained spot for composting that is semi-shaded and not right against your house or the neighbour’s fence.

Be aware that an open compost bin will attract rodents and dogs.  To avoid this it is best to have a bin with a lid.  A wire cage can be used and should have a wire bottom too as rats will dig under to get to the food scraps. An open bottom to the container is needed so that it can drain after rains and allow worms to enter and help break down the compost.

Place your compost not to far from your kitchen and close to your garden for easy access.  Ensure you have a tap or hose for watering within reach of your compost bin.

Choose a good balance of sun and shade, no afternoon heat as this will overheat the compost and kill off the microbes which are beneficial for the decomposing process. A shady area will also help prevent water evaporation and keep your compost bin from drying out too fast.

Compost bins can also be used by people living in apartments by choosing a flat, semi-shaded position, on a balcony, courtyard or carport.  Remember to keep it out of the midday and hot afternoon sun!

3. a. Setting up your COLD compost pile

With cold composting, the ratios are not so important; but rule of thumb is to aim for more brown than green so your compost pile doesn’t get too wet or smelly and air has a chance to circulate.

If you don’t have a bin, you can start with your pile directly on the bare ground but if you have pets or rodents I suggest a wire mesh cage (bird cage wire is best) with a bottom and a lid.   Then start with a layer of brown material—leaves, small branches, dry lawn clippings, newspaper, or torn-up cardboard—to a depth of six inches.

To this layer, add your kitchen scraps and place them more towards the centre than the sides.  Add about 10-15 cms of green material and another layer of brown stuff, 10-15 cm thick. Repeat this when you have acquired more scraps and always end with brown material on top.

The green and brown layers should be added with about 2/3 brown to 1/3 green once or twice a week. Aside from this, it is important to aerate the compost every week or two before adding more green stuff.  This can be done by stirring and mixing the compost. Micro-organisms need air and moisture to help to break down the waste material.

While stirring the compost, check for moisture, content especially during the hot dry months.  The pile should be damp not wet, similar to the wetness of a damp sponge. If it’s dry, sprinkling with water will help to speed up the composting procedure.

Once your compost bin is full or after about four, six to eight months, a new bin can be started and the old bin left to completely decompose or use what is ready for use.  Some compost will take longer depending on the weather.  You will know if it’s ready when your pile is the same size or smaller than when you started, even though you have been adding to it.  This can take up to 8 months, depending on the speed of the decomposition process.  At the end of the process, the pile can be up to 70-80% smaller than when you started.  Your compost is now well decomposed, mature and ready for use.

How to use your compost

To know if your compost is ready, keep an eye on the bottom of the heap and the size of your compost pile.  If the heap has decreased in volume over 4-6 weeks it is breaking down (even if slowly).  At the bottom of the compost, a layer of dark brown composted matter will develop; this is the initial layers turning into compost even while you are still adding new layers on top.

When mature, the compost should be dark brown, moist and crumbly in appearance with a good organic earthy smell.  You shouldn’t be able to recognise any food or vegetation scraps within your composted material.

How fast your pile matured will depend on how fast the compost has degraded and how much you have been adding to your pile.  Cold compost is very dependent on the local air temperature and moisture conditions. But if you are adding about a bucket of material to your pile every week, you should have at least 4-5 buckets of compost at the end of 6-8 months.

b. Setting up your HOT compost pile

Hot compost goes through a very similar process to the COLD compost but relies on the heat from the decomposing matter to speed up the process and kill off unwanted pathogens and seeds.

Begin with a brown layer of small twigs, old mulch, or potting mix for good airflow and drainage. Add alternating layers of green and brown materials until the bin is about one-third to half full.  Sprinkle with water after each layer to keep it moist. When layering your compost, aim for a ratio of two-parts brown material to one-part green.

Some examples of ‘green’ products – nitrogen-rich include:

• fruit and vegetable scraps
• garden trimmings and prunings
• grass clippings
• tea leaves and coffee grounds
• chicken, cow, and horse manure.

Some examples of ‘brown’ products – carbon-rich include:

• dried leaves and grass
• straw
• small twigs
• shredded paper.

Once you are happy with the pile, top it off with a layer of soil (if you do not want to be adding more layers).  You can also cover with a tarp during the wet season. This helps keep in heat and moisture while also ‘activating’ the pile with microorganisms, which speeds up the composting process. Some activating materials you can use include comfrey leaves, coffee grounds, garden soil, cow, chicken, or horse manure, or worm juice.

Within a day or two, you will be able to feel the heat within the pile as the decomposition process begins

A few additional things to keep in mind:

• Smaller items decompose faster, so chop or shred them if possible.
• Boost the breakdown process by using a diverse range of materials in your compost mix.
• Keep a heap of brown materials handy near your compost. You can use them to cover nitrogen-rich food scraps for a balanced compost pile.
• Ash from burning rubbish (no plastics) off or fire place ash can also be added to help reduce smell and will add nutrients to the compost.

4. Maintaining your compost

To maintain your compost, keep adding materials regularly, ensuring a good mix of green and brown throughout the bin.

Add air every week or two by turning the compost with a compost screw, garden fork, or a stake. The more you aerate the compost, the faster it will break down.

If the compost starts smelling, add carbon-rich (brown) materials and ash and aerate the heap.

If your compost is dry and slow to break down, add water, some activating ingredients, and turn it more frequently.

Compost is ready when it looks like a dark, rich soil.  This can take up to a few months. Do NOT use compost before it has had a chance to fully break down. Immature compost will continue to heat up and could harm your plants.

How to speed up your compost:

If you add water (not too much, but enough to make it like a damp sponge level of moisture), and if you keep your compost under a tarp, which can warm it up, both of these may help speed up composting. Just be sure that it’s not getting too hot under the tarp—remember your compost pile shouldn’t be in the sunshine. Your bacteria and microorganisms will die at temperatures over 150 degrees.

Which method is better, HOT or COLD?

It’s your choice, you can also switch from one method to another (and back again) depending on your time, season or needs.  Hot composting simply requires more monitoring, care, and attention, so if you have started a cold compost pile, you can switch to hot if you want to—they both work with the same materials and similar quantities.

Where can I use compost?

• House plants and propagating mix for seedlings: compost can be used as a soil improver when repotting houseplants or mix it 50/50 with potting soil when starting seeds.
• Garden beds and containers: compost can be added directly to the soil of a garden bed or container.
• Compost is best added before planting in the spring or after harvest in the autumn.
• Tree, shrub and ornamental planting: add compost to the soil when you are planting or directly into the beds as you plant annual or perennial flowers or bulbs.
• Mulching with compost: compost (especially if it’s not 100% finished breaking down) can be used as mulch to keep weeds down, while simultaneously nourishing the soil as it finishes breaking down.

By composting at home, you are helping to feed the earth and prevent waste.  Your plants and the planet will thank you for it.