HOW TO: Compost

We’ve all heard of it, but do we really know how to compost? Composting isn’t as simple as throwing your food waste together and leaving it to decompose. There is a science to the process, but if you follow a few basic steps, making your own compost at home is easy.

In honour of World Compost Week, Food & Trees for Africa (FTFA) has put together a quick guide to composting in five easy steps:

1. Collect your materials

Your compost heap should contain a mixture of different organic materials.

• Carbon (brown material): sticks, dry grass, dry leaves, straw, shredded newspaper and cardboard.
• Nitrogen (green material): your food waste. Only use raw vegetable waste. Avoid highly acidic food like citrus, pickles and tomatoes. Also add green grass-clippings or leaves, and fresh manure.
• Larger sticks/logs for the base of the compost heap. This forms the aeration layer.
• Activators: Manure, green comfrey and/or yarrow leaves, worm tea (natural liquid fertiliser made by soaking worm manure in water) and worm leachate. These activators provide additional nitrogen to speed up the composting process.

Your compost is also going to need water – preferably rainwater or from a borehole.

2. Prepare your site

Your site must be accessible, so you can regularly tend to it. 

You can build a simple wooden box (used pallets make excellent building material) to enclose your compost heap. The bigger the better, but a decent size is 2m x 2m x 1m.

Place larger sticks and logs directly on the ground to prevent waterlogging and ensure airflow from the base of the heap.

3. Build your compost heap

Layer your materials, as you construct your heap, watering each layer as you build. 

Alternate 15cm-thick brown layer with a 5cm-thick layer of green material. After every two layers, add an activator. Build your heap up to a height of one metre.

4. Cover and let the heap decompose

Cover your heap entirely with mulch to keep in moisture. 

Turn your compost at least once a week to aerate it. Composting is controlled aerobic biodegradation – the breakdown of organic materials into their basic elements and humic material (the basis of compost) – in the presence of oxygen. Turning your compost exposes it to oxygen, enabling the aerobic process.

Biodegradation is done by a complex interacting food web of living organisms, including fungi, microbes, and tiny invertebrates.

The humic material we’re after is a part of the soil that holds recycled nutrients. It is usually darker and moister than the rest of the soil.

Compost goes through three thermal phases, but essentially it needs to get really hot. Why? When it reaches 70 ºC, pathogens are killed off, making it safe for plants and humans.

As organic resources are depleted and converted, the process slows and compost begins to cool and mature. The entire process should take about four weeks.

5. Sift and repeat

Use a sieve to sift out the ready compost – the dark brown or black soil (humic material). The remaining material that hasn’t broken down yet can be used as an activator in your next heap, which you can get started straight away. Remember, you can never have too much compost!

For an easy-to-follow guide to composting, you can download FTFA’s educational composting guide. Happy composting!