The phrase "greens and browns" is shorthand for two kinds of material a pile needs. Greens are moist and rich in nitrogen, browns are dry and rich in carbon, and microbes use both to break organic matter down into compost. Getting the mix roughly right is the single habit that prevents most odour and slow-pile complaints.
What counts as a green
Greens are the fresh, often wet materials from the kitchen and garden. They supply nitrogen and bring moisture into the pile.
- Vegetable and fruit trimmings
- Coffee grounds and loose tea
- Fresh grass clippings and soft garden prunings
- Plant-based leftovers without oil, dairy, or meat
What counts as a brown
Browns are the dry, fibrous materials that supply carbon and structure. They keep the pile airy and absorb the moisture that greens release.
- Dry autumn leaves
- Shredded uncoated paper and plain cardboard
- Straw and dry plant stalks
- Untreated wood chips and sawdust in small amounts
Judge by feel, not by the gram
Home composting works on volume and observation rather than precise measurement. A practical starting point is roughly equal volumes of greens and browns, adjusted by what the pile is telling you. A wet, dense, sour pile wants more browns; a dry pile that refuses to heat wants more greens and water.
Reading the pile
A balanced, active pile smells earthy and feels like a wrung-out sponge. Two signals point to an imbalance worth correcting:
| Signal | Likely cause | Adjustment |
|---|---|---|
| Ammonia or sour smell, wet and matted | Too many greens, not enough air | Mix in browns and turn the pile |
| Dry, pale, little activity | Too many browns or too dry | Add greens and a little water |
| Slow but no smell | Pieces too large or pile too small | Chop material and build more volume |
Storing the autumn surplus
In much of Canada, browns and greens do not arrive at the same time. Leaves fall heavily over a few autumn weeks, while kitchen greens are produced year round. Setting aside bagged or binned dry leaves in autumn gives a ready supply of browns to balance kitchen scraps through winter and spring, when fresh dry material is scarce. A simple stockpile beside the pile is often enough.
For general background on what household organics can be composted, municipal waste programs and the home-composting guidance from the US EPA offer publicly available overviews that align with common Canadian practice.