Composting: hot, cold & worms
Turn kitchen and garden waste into the black gold that powers a no-dig garden.
9 cards · 6 quiz questions · 8 min read
If no-dig gardening runs on compost, then knowing how to make it is the engine room of the whole system. The good news: compost essentially makes itself. Your job is just to give the decomposers the conditions they like.
Greens, browns, air and water
Composting is microbial digestion, and the microbes need a balanced diet:
- Greens — wet and nitrogen-rich: kitchen scraps, fresh grass, manure, coffee grounds.
- Browns — dry and carbon-rich: cardboard, dead leaves, straw, woodchip.
Aim for a carbon-to-nitrogen ratio of around 25–30:1, which in practice means roughly balancing browns and greens by volume and adjusting by feel. Add two more ingredients — air (so it stays aerobic and sweet-smelling) and moisture (damp as a wrung-out sponge) — and decomposition takes care of itself.
Most problems are just this balance tipping over:
Slimy and smelly? Too much green, not enough air → add browns and turn it. Dry and inert? Too much brown, not enough moisture or nitrogen → add greens and water.
Three ways to do it
Cold composting
The default for most gardens: you add material gradually as it arises and let it rot down slowly over six to twelve months. Minimal effort, but the heap never gets hot, so it won’t kill weed seeds or pathogens — keep those out.
Hot composting
Build a heap of about a cubic metre all at once with a good C:N balance, then turn it for aeration. Microbial activity drives the core to 50–65 °C, which sanitises the material — killing weed seeds and disease — and produces finished compost in a matter of weeks. More work, much faster, higher quality.
Vermicomposting
Composting with worms in a contained wormery. Tiger worms eat soft kitchen scraps and excrete fine, nutrient-dense castings. It’s the ideal route if you lack space for a heap — a wormery happily lives on a balcony or in a shed.
Knowing when it’s done
Finished compost is dark, crumbly and smells of woodland floor. The original scraps are no longer recognisable, the heap has cooled, and it has stopped shrinking. Spread a few centimetres over your beds, let the worms take it down, and you’ve closed the loop — yesterday’s kitchen waste feeding next year’s harvest.
Which of these is a "green" in composting terms?
Sources
- Royal Horticultural Society — RHS guide to composting website Authoritative UK guidance on greens, browns and compost methods.
- Jeff Lowenfels & Wayne Lewis — Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web book Covers the microbial processes that drive decomposition.