Compost: cold and hot, from waste to humus

In short

• Aim for a starting C:N of about 25–35 : 1, moisture like a wrung-out sponge (50–60 %) and a heap of at least 1 m³ (about 35 cu ft).
• A hot heap sanitises manure and weeds only when the centre holds 55 °C (131 °F) or more for at least 3 days — and about 15 days with 5 turnings for an open heap.
• A cold heap is a safe savings box for leaves and plant waste, but it does not kill pathogens or seed: no fresh manure and no seeding weeds go in.
• Compost is mature when it doesn't heat up after turning, smells of woodland soil and passes the cress germination test.
• Vegetable beds: 2–4 kg per m² (4–6 L) a year for maintenance; a new bed gets 2–5 cm once.

What's inside

Chapters

1. What happens in the heap
2. Browns and greens in numbers
3. Moisture, air and size
4. The hot heap, step by step
5. Cold compost and leaf mould
6. What to do with problem waste
7. A compost corner that works
8. When compost is mature
9. How much, and how, in the garden
10. Common mistakes
11. Printable checklist

Worksheets

• Mix calculator
• Compost bay plan
• Hot heap log
• Maturity test
• Compost calendar
• Compost record