Guide · The Almanac
Complete Guide to Composting at Home
Turn kitchen scraps and yard waste into rich garden soil — no special equipment required.
What is composting?
Composting is the controlled decomposition of organic matter — food scraps, yard waste, and other biodegradable materials — into a dark, crumbly, nutrient-rich soil amendment called compost. It is one of the most effective things a home gardener can do: it improves soil structure, feeds soil microbes, retains moisture, and reduces the need for synthetic fertilizers.
The process is driven by microorganisms (bacteria and fungi) that break down organic matter. Your job is to give them the right conditions: the correct balance of carbon and nitrogen, adequate moisture, and enough oxygen.
Greens vs browns: the foundation
Every compost pile is built from two types of materials.
Greens · N-rich
Fresh, moist materials high in nitrogen. They provide protein for microbes and speed up decomposition.
Grass clippings, food scraps, coffee grounds, fresh manure, green leaves.
Browns · C-rich
Dry, fibrous materials high in carbon. They provide energy for microbes and create air pockets that keep the pile from compacting.
Dry leaves, straw, cardboard, wood chips, newspaper.
A common rule of thumb is a 3:1 ratio of browns to greens by volume. However, the more precise measure is the carbon-to-nitrogen (C:N) ratio of the combined pile.
The C:N ratio explained
The carbon-to-nitrogen ratio is the single most important factor in composting speed and quality. The ideal range for active composting is 25:1 to 30:1 — meaning 25–30 parts carbon for every 1 part nitrogen by weight.
- Too much nitrogen (C:N below 20:1): The pile heats up fast but smells like ammonia. Nitrogen is lost as gas. Add more browns.
- Too much carbon (C:N above 40:1): Decomposition slows dramatically. The pile stays cool and takes months or years to break down. Add more greens.
- Ideal range (25:1–30:1): The pile heats to 130–160°F (55–70°C), kills weed seeds and pathogens, and produces finished compost in 4–8 weeks.
C:N ratios of common materials
| Material | Type | C:N | Tips |
|---|---|---|---|
| Grass Clippings | Green | 20:1 | Add in thin layers to prevent matting |
| Food Scraps (veg/fruit) | Green | 15:1 | Bury in centre to deter pests |
| Coffee Grounds | Green | 20:1 | Excellent activator; use freely |
| Fresh Manure | Green | 15:1 | Chicken, cow, horse — not pet waste |
| Green Leaves | Green | 25:1 | Great balance of N and C |
| Dry Leaves | Brown | 60:1 | Shred for faster breakdown |
| Straw | Brown | 80:1 | Good bulking agent; improves aeration |
| Cardboard | Brown | 350:1 | Remove tape; tear into pieces |
| Wood Chips | Brown | 400:1 | Best for slow cold composting |
| Sawdust | Brown | 325:1 | Use untreated wood only |
| Newspaper | Brown | 175:1 | Shred; avoid glossy paper |
| Corn Stalks | Brown | 75:1 | Chop into 2–3 inch pieces |
Hot vs cold composting
Hot composting
4–8 weeks · hands-on
- — Finished in 4–8 weeks
- — Kills weed seeds and pathogens
- — Higher quality compost
- — Requires turning every 1–2 weeks
- — Needs correct C:N ratio and moisture
Cold composting
3–6 months · hands-off
- — Minimal effort — just pile and wait
- — Good for small amounts of material
- — No turning required
- — Takes 3–6 months or longer
- — May not kill weed seeds
Troubleshooting common problems
Pile smells like rotten eggs
Cause — Too wet and anaerobic (no oxygen).
Fix — Turn the pile to add air. Add dry browns (straw, dry leaves) to absorb excess moisture. Ensure the bin has drainage.
Pile smells like ammonia
Cause — Too much nitrogen (greens).
Fix — Add carbon-rich browns — dry leaves, cardboard, or straw. Turn the pile to release the ammonia gas.
Pile is not heating up
Cause — Too much carbon, too dry, or pile is too small.
Fix — Add fresh greens (grass clippings, food scraps). Water until the pile feels like a wrung-out sponge. Ensure the pile is at least 3×3×3 ft — smaller piles cannot retain heat.
Pile is attracting pests
Cause — Meat, dairy, or oily food scraps; food scraps on the surface.
Fix — Never add meat, dairy, or cooked food. Bury food scraps in the centre of the pile. Use a bin with a lid or hardware cloth base.
Compost is taking too long
Cause — Wrong C:N ratio, too dry, not turned, or materials too large.
Fix — Chop or shred materials into 2–3 inch pieces. Turn every 1–2 weeks. Check moisture. Adjust C:N ratio using the Compost Calculator.
What NOT to compost
- Meat, fish, and bones — attract rodents and create odours.
- Dairy products and oily foods — same issues as meat.
- Pet waste (dogs, cats) — may contain pathogens harmful to humans.
- Diseased plants — pathogens may survive cold composting.
- Treated wood or sawdust — may contain toxic preservatives.
- Invasive weeds that have gone to seed — seeds may survive and spread.
- Glossy or coated paper — does not break down well.
How to use finished compost
Finished compost is dark, crumbly, and smells earthy — like a forest floor. It should not smell like the original materials. Here is how to use it:
- Soil amendment: Mix 2–4 inches into the top 6–8 inches of garden beds before planting.
- Mulch: Apply 1–2 inches around plants to retain moisture and suppress weeds.
- Potting mix: Blend up to 30% compost with potting soil for containers.
- Lawn top-dressing: Spread a thin layer (¼ inch) over lawn in spring or fall to improve soil health.
Related tools
How much compost do I need? Compost calculator
Cubic yards, bag count, and depth for raised beds and lawns; plus C:N ratios for 20 materials.
Vegetable seed spacing calculator
Estimate bed area and plant count before deciding how much finished compost to spread.
Soil pH calculator for vegetable beds
Check whether compost-amended beds still need lime or sulfur for the crop you want to grow.