What you need
A compost bin
Advertisement
Kitchen waste
Plenty of waste low in nitrogen, such as cardboard or sawdust
WE ALL like to get something for nothing, and one way to do that in gardening is to make your own compost from kitchen and garden waste. If all goes well, you end up with an earthy, fine brown crumb within a couple of years, which adds nutrients and structure to your soil. But get things wrong, and it turns into a slimy, stinking mess. So what are the dos and don’ts of composting?
The process is all about exploiting the animals and microorganisms that break down organic matter, recycling nutrients through successive plant generations. Storing it in a pile or compost bin retains more heat to speed things up.
For raw materials, think in terms of greens and browns. This relates not to colour, but to the relative nitrogen and carbon content of the materials. Green waste is relatively richer in nitrogen and comprises things like grass clippings and fruit and vegetable scraps. Too many greens suppress the desired microbial processes, releasing smelly ammonia gas. Brown waste, which is richer in carbon, includes cardboard, sawdust and autumn leaves. Aim to dilute nitrogenous green waste with three-to-four times as much brown material.
For those like me, who are chiefly looking for ways to dispose of food scraps, it can be hard to get enough browns. I used to use all my household cardboard waste, but food packaging is often covered with thin films or labels and I got fed up picking bits of plastic out of my compost. Now I stick to cardboard I’m sure is uncontaminated, like the tubes in toilet rolls, or shredded corrugated cardboard boxes. Sawdust works particularly well if you can lay your hands on any.
You also need to manage the oxygen and moisture levels of your heap. The better you do this, the faster it will make usable compost. Improve aeration by turning things over a few times a year. I do this by lifting the container off the heap and forking the contents into another bin.
You may also need to water your compost heap if it looks too dry. But don’t let it get too waterlogged or anaerobic decomposition will leave the heap smelling like rotten eggs. “Most composters learn through a process of trial and error,” says Danielle Purkiss at University College London.
Purkiss is running an experiment to see how long “biodegradable” plastics rot down in home compost heaps. Paradoxically, these cause more of a problem for expert composters’ heaps. The label “biodegradable” is given if a substance rots in 12 months, but experienced hands may achieve a faster compost life cycle than this.
Although I’m not an expert, I can vouch for how satisfying it is when your hard work results in a finished product you can use on your garden. “It’s a kind of alchemy,” says Purkiss.
Science of gardening appears every four weeks
Next week
Citizen science
These articles are posted each week at
