How to - Techniques

Compost basics

Laura Langston
Photography by
Tai Kim McPhail

Turn kitchen scraps into food for your garden

Start your compost pile by laying down about 15 centimetres of rough plant material, such as stalks or twigs, to encourage air flow into the pile. Add a nitrogen layer of kitchen scraps and/or fresh plant trimmings, followed by a carbon layer of dry, brown plant material. Layers should be between five and 15 centimetres deep (see “Size Matters” below). One layer each of nitrogens and carbons is adequate to start; follow with a 2.5- to five-centimetre layer of garden soil or finished compost. Repeat with alternating nitrogen and carbon layers as kitchen waste and trimmings become available, but always end with a carbon layer on top to discourage flies and rodents. Aim for a pile that's between one cubic metre and 3.5 cubic metres in size.

Size Matters Should a compost layer be five or 15 centimetres deep? It depends on the season, region and the size of particles and type of materials in each layer. The goal is to promote the speedy breakdown of ingredients. So it follows that thinner layers are more efficient in cold regions and weather; and are also appropriate when the ingredients are chunky. Nitrogen-rich layers (especially those with fresh grass clippings) heat up quickly, so they can be thicker than carbon layers, which take longer to decompose.

Compost piles sometimes need a kick-start in spring to get them working efficiently again. And, depending on the weather, they might need adjusting during the growing season, too.

Bad odour (not enough air circulation or pile too wet)
Turn pile; add coarse, dry material such as straw and shredded leaves
Too dry
Mix in a few handfuls of soil and some moist kitchen scraps or coffee grounds; water pile, cover and let sit. Check weekly; if it's still too dry, repeat
Too wet
Turn pile and add dry materials such as straw, dry leaves (not fresh), sawdust, even lint from the dryer. Keep it uncovered (except in periods of prolonged heavy rain) and check weekly. Apply the touch test: a handful of material should be as moist as a wrung-out sponge
Too cold or too weedy
To heat things up (which helps to kill weed seeds), add some high-nitrogen materials such as kitchen scraps, fresh grass clippings or manure
Failure to decompose
If there are layers of fresh leaves or grass clippings, break them up by mixing in straw, hay (but no hay seeds) or dry leaves. If large chunks are not decomposing, sift pile through a screen or use a soil shredder. The resulting fine material can be used as the base for a new compost heap
Damp and warm in the middle but dry elsewhere
Pile is too small; collect more material and mix it in. Or turn the heap more frequently
Damp and sweet-smelling but will not heat up
Needs more nitrogen; mix in fresh grass clippings or fresh manure
Pest infestations (dogs, rodents, insects such as flies, bees, wasps and ants) Improper food scraps added; don't add meat, fats, bones or pet waste. Cover food scraps with soil or other carbon materials; turn pile weekly

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