THE MAGIC OF COMPOSTING
Like soil – and like us, really – compost needs certain things to thrive. Food, air, water are the basics. The food is plant or animal waste. Air you get by regularly mixing and turning the compost. Your compost should also be damp, so wet it often. And it should warm up, as all those microbes get to work.
Most home compost is hard to manage if you add animal waste (meat scraps), unless you can keep rats and other vermin out. Using a bokashi bin – a Japanese-designed bio-digester – might be better in this case.
In terms of ratios, about twice as much 'brown' garden waste to 'green' is best. So, twice as many brown dried leaves as green lawn clippings, for instance. You don't have to be exact, but this is a good starting point. If you're unsure, having too much carbon (brown waste) is better for the smell, and for the environment, as it emits less nitrous oxide and methane. Think of brown waste as things that will burn cleanly – so, sawdust from old wood, compared to green, the tops of trees that have been mulched. Or hay as brown, and freshly cut lawn clippings as green.
Common composting mistakes
Smelly, slimy compost: Too much nitrogen. You need to add more carbon in the form of dry leaves or dry grass clippings. You could add hay, but you might also be adding weed seeds if your compost doesn't get very hot. Early on, you could use sawdust or shredded paper, which will take longer to break down. A mix of different carbon sources is usually best.
Dry on top, smelly inside: Probably not enough air. Turn the compost regularly (weekly is good) to mix and aerate.
Dry right through: Not enough water, possibly? Wet it each week as you turn it. It could also contain too much carbon, but this is usually not the case for home gardens. Add green grass clippings, or more food waste.
Chunky compost: Possibly lots of things from the garden that are hard to break down. If everything else is going well, you can make the compost and sieve these out, then return the big bits to your compost.
Cold compost: It's just working slowly. This will take a long time, so your compost may need more food, or more water, to jumpstart the microbial life. Hot compost can be ready in a matter of weeks, but cool compost can take months to mature.
When your compost is ready, it should have an attractive earthy smell, and crumble easily through your fingers. Everything small should have broken down into a very dark substance, which is essentially pure humus, ready to use on the garden. If you're not sure your compost is done, and are worried it might have dangerous bacteria (the kind you get in poo, rotting food and the like), you can still use it. Just shovel it around the base of fruit trees rather than your lettuces, so it doesn't get into your dinner.
"Soil: The incredible story of what keeps the earth, and us, healthy" - Matthew Evans
