Understanding Composting
Composting is the natural process of recycling organic matter into a nutrient-rich soil amendment. The key to successful composting is maintaining the right carbon-to-nitrogen (C:N) ratio. Microorganisms that break down organic material need both carbon (for energy) and nitrogen (for protein synthesis).
The ideal C:N ratio for active composting is between 25:1 and 35:1. Too much carbon (high ratio) slows decomposition; too much nitrogen (low ratio) creates ammonia odors and attracts pests.
Composting Formulas
Common Composting Materials
| Material | Type | C:N Ratio |
|---|---|---|
| Grass clippings | Green | 15:1 |
| Food scraps | Green | 20:1 |
| Coffee grounds | Green | 12:1 |
| Dry leaves | Brown | 60:1 |
| Cardboard | Brown | 350:1 |
| Straw | Brown | 80:1 |
| Sawdust | Brown | 500:1 |
| Wood chips | Brown | 400:1 |
Frequently Asked Questions
What is the ideal green-to-brown ratio by volume?
A good starting point is 1 part green to 3 parts brown by volume. Since green materials are denser and richer in nitrogen, this volumetric ratio approximates the ideal 25-35:1 C:N ratio.
How long does composting take?
Hot composting (with regular turning) takes 4-8 weeks. Cold composting (passive pile) takes 6-12 months. Turning the pile every 1-2 weeks, maintaining moisture, and achieving the right C:N ratio speeds up the process significantly.
What size compost bin do I need?
A minimum of 3x3x3 feet (27 cu ft) is needed to maintain heat for active composting. Larger bins (4x4x4 or 5x5x5) work more efficiently. For a family of four, plan for 4-6 cubic feet of kitchen scraps per month.