How to Make Compost at Home: A Beginner's Guide
Composting turns kitchen scraps and fallen leaves into the best soil amendment money can't buy. This guide explains the greens-and-browns balance, moisture, airflow, and how to tell when your compost is actually finished.
What a compost pile actually needs
Composting comes down to four things: the right mix of materials, moisture, air, and enough volume to hold heat. You want roughly two to three parts "browns" to one part "greens" by volume. Keep the pile as damp as a wrung-out sponge, and turn it so the centre keeps getting oxygen. A pile smaller than about one cubic metre (3 ft x 3 ft x 3 ft) struggles to heat up, so build volume rather than spreading material thin.
Sorting greens and browns
Greens are fresh, moist, nitrogen-rich materials: vegetable peelings, fruit scraps, grass clippings, tea leaves and coffee grounds. Browns are dry, carbon-rich materials: fallen leaves, straw, shredded newspaper, plain cardboard and sawdust from untreated wood. If your pile smells sour or looks slimy, you have too many greens, so add browns and turn it. If it sits dry and does nothing, add greens and a splash of water to wake it up.
Choosing a bin or building a heap
An open heap works fine, but a bin keeps things tidy and holds moisture better. Use a bottomless bin or a three-sided bay with gaps for airflow, sitting on bare soil so worms and microbes can move in from below. Sealed plastic tumblers are convenient for small kitchens but dry out and cool fast, which slows decomposition. In a tiny yard or on a balcony, a worm bin turns kitchen scraps into castings with no smell at all.
What to keep out
Leave out meat, fish, dairy and greasy food, which attract rodents and turn foul as they rot. Skip dog and cat waste because it can carry pathogens, and skip diseased plants or perennial weed roots that survive most home piles. Glossy printed paper and anything treated with pesticides or preservatives should also stay out. The occasional stray item won't ruin a pile, but keeping these out makes the whole process cleaner and safer.
Turning, moisture and troubleshooting
Turn the pile every one to two weeks with a fork, pulling the outside material into the middle. A healthy pile reaches 55-70C (130-160F) in the centre within a few days, and that heat kills many weed seeds and pathogens. If it stays cold, it is usually too dry or short on nitrogen. If it smells of ammonia, add browns and turn again. A cold pile still breaks down, it just takes six to twelve months instead of eight to twelve weeks.
Knowing when it is ready
Finished compost is dark, crumbly and smells like forest floor, and you should no longer recognise the original ingredients. Screen out sticks and lumps and toss them into the next pile as starter material. Spread it as a 2-5 cm top dressing, work it into planting holes, or steep it in water for a quick compost tea. One mature pile feeds a surprising amount of garden, so start small and keep the cycle running all year.
The bottom line
Composting is really just managing moisture, air and the greens-to-browns ratio. Aim for two to three parts browns to one part greens, keep the pile as damp as a wrung-out sponge, and turn it every week or two. Even a lazy pile gives you dark, free soil food within a season.