The key to creating good compost is to think like a microbe.
Like us, microbes need air, water and food. Get that right, and the local microorganisms and insects will soon transform your kitchen and garden waste into rich, healthy, sweet-smelling compost. A handful of compost can contain a billion microorganisms.
Costa sets up a simple system with two upright plastic compost bins – the ones with no base, although he covers them with some chicken wire to keep out vermin. Simply find a spot that’s out of the way, not in full sun, away from tree roots, and sitting on soil. Ideally you have two bins so, after one has been filled, you can leave it to decompose while you fill the second bin.
There’s no secret recipe or ‘right or wrong’ to making compost, but it’s important to keep a balance of carbon-rich, brown material (used for energy) and nitrogen-rich greens (used to reproduce and grow).
Green is the nitrogen-rich fresh material that includes kitchen scraps, grass clippings, fresh weeds, coffee grounds and tea leaves – even chicken feathers and poo.
Brown material can include dry leaves, straw from animal bedding, wood chips, shredded paper, and ripped-up egg cartons.
When you’re starting, it’s also best to keep meat, wheat and dairy out, as they can attract vermin.
Start with a layer of dry carbon material, which has air pocked and allows oxygen to get into the system. Then, every time you add a layer of green material, add a layer of brown on top, and water it in. Costa starts this layering even in his kitchen tidy.
Rather than laying newspaper flat, rip it into streamers and try to incorporate as much air with it as possible – Costa has a little dance that helps do this….
Adding layers gradually like this and then leaving it to decompose is called cold composting. There is also a system that speeds up the process, called hot composting; this requires a larger compost pile, specific brown and green ratios, and regular turning.
Unless you are running a large, hot-composting heap in excess of 1m3, avoid introducing plants with pests or pathogens (like mildews) or weeds with seed heads or bulbs – these can persist in compost and be spread around the garden via the compost later.
But, don’t just bin those weeds – you can use them to make a weed tea, a DIY liquid fertiliser that’s good for your garden and your compost heap.
Whack your weeds into an old pillowcase, hessian bag, or wrap them in shadecloth – the greener and fresher the weeds, the better! Bunging weeds into a bag stops the seeds being spread, and the brew from clogging your watering-can rose.
Dump this weed ‘tea bag’ into a big bucket of water, cover, and let it sit for a couple of days, stirring when you remember.
Once your weed tea has steeped, use the tea diluted in a ratio of 1:3 in a watering can and use it to water edible plants such as leafy greens, or pour it on your compost heap to give it a kick along!
The watered-down weeds can go into your green-waste bin – they’ve served their purpose.
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