Updated: Sep 29, 2020
The greenest thing a food gardener can do (apart from planting the green stuff) is to make compost. It ticks each box for all the four ‘R’s’: recycle, reuse, repurpose and reduce.
All the garden and organic household waste (scraps, paper, cardboard, dog hair) that would have gone to the landfill goes into the compost. Then there is the fifth ‘R’, regenerate, which is the effect that compost has on the soil.
Compost is not only free nutrition, it is the easiest and cheapest way to condition the soil, improve drainage and aid water retention.
Anyone with a garden, even just a few pots, can make compost. The method you use depends on space and affordability.
Traditional compost heap
This is the most cost-effective option but needs space. It is suitable for gardens where the heap can be placed out of sight, usually at the bottom of the garden. The site needs to be level and on soil so that the earthworms can do their work. Start with a layer of sticks or small branches (for drainage) and build it up in layers of brown material (leaves, paper, cardboard) for carbon and green (vegetable scraps, grass cuttings, prunings) for nitrogen. A layer of manure every now and then acts as a compost activator. Turn regularly to aerate. Don’t go much higher than 1.5m.
Home-made open bins
The three-bin compost system is neater than the traditional heap, more efficient, and easier to process and harvest large volumes of compost. If there is not enough space for three bins, just make one. Keep it affordable by making your own from recycled wood and netting wire or wooden pallets held together by cable ties. The front panel of each bin should be removeable so that material is easy to move or harvest. This system allows both hot and cold composting.
This is a tidy, self-contained, rat-proof composting option for small gardens that don’t generate a large volume of waste. The sturdy bins are usually made from recycled plastic, are filled from the top and sealed with a lid. Not being able to turn the material does slow down decomposition. Remove the decomposed material from the bottom (some have an opening) or move the bin so that the material drops out. Bag the good stuff, return the remainder to the bin and top up with new material.
This is another option for limited space. It is more effective than a bin, producing compost more quickly, and harvesting is easier. Like a bin, the volume is limited. The tumbler, usually made from heavy plastic, is supported by a frame and raised off the ground so that it can be turned with a handle. That takes the hard work out of turning the compost. To increase the diversity of microbes in the bin, add a spade of soil every now and then.
Vermicomposting differs from other composting because it doesn’t include garden waste, only household scraps, paper and cardboard that is broken down by specific compost worms (Eisenia fetida). Wormeries are small, self-contained and usually odour free, making them ideal systems for indoors or small outdoor spaces, although most gardeners like to have a wormery in addition to the conventional compost. That’s because the worm tea (liquid leeched from the wormery) and the worm castings are highly nutritious. Wormeries can range from a home-made bucket system to a more sophisticated, but expensive, system for easier harvesting.
No-fuss compost pits and sheet mulching
This also differs from conventional compost making because the end product stays in place. This method is good for making a fertile garden bed but can take up to six months before material is broken down enough for planting. For a deep bed, dig a hole or trench and fill it with organic material. If it is not possible to make a hole, build up layers on top of the soil (also called lasagne gardening) so that the result is a raised bed. It is a good way to use up lots of organic matter and it looks neat.
While there are many things that can go into a compost heap, there are some items to be avoided like cooked food. This is were bokashi can make a difference. A bokashi composter conveniently composts all food waste indoors using a wheat bran inoculated with probiotics.
Activators start the process of composting with a bang and speed up the process so that you can get to the good stuff within 6 weeks. Most activators contain strains of bacteria that degrade waster with some able to reduce smells.
Composting do’s and don’ts
Do put in the right stuff: veggie and fruit peelings, teabags, coffee grounds, wood ash, plant prunings, grass cuttings, fallen leaves, cardboard egg boxes, crushed eggshells, soft cardboard, newspaper and paper.
Don’t put in the wrong stuff: meat or dairy products, potato peels, animal faeces, diseased plants, weeds with seed heads or flowers, plastics, glass or metal.
Do use a balanced mix of green and brown material. Too much green makes it too wet, and too much brown makes it too dry.
Do aerate by turning regularly to improve decomposition. Adding scrunched up paper or cardboard to a compost bin will create air pockets.
Do use natural compost activators like manure, or herbs like comfrey, yarrow and borage, to help the compost break down more quickly and to add minerals.
What’s the difference between hot and cold composting?
You may hear the terms hot and cold composting bandied about. It is not as technical or as flammable as it sounds.
The advantage of hot composting is that it breaks down materials faster, so that finished compost is available within about three months. High-nitrogen materials are used to heat up the mix, but these must be balanced with carbon materials. The ratio is 2 parts carbon to 1 part nitrogen. The pile needs to be consistently damp and turned often to aerate it and to maintain its internal heat.
Cold composting is simply a pile of garden waste that is left to decompose in its own time. No fuss and no effort, but it can take a year to fully decompose. It does not kill off garden weeds or pathogens. Chop up the material into small pieces to speed up the decomposition.