The carbon and nitrogen ratio
Getting the mix right
Make sure you have the right mix of brown and green material in your compost bin. This will ensure you get the correct carbon and nitrogen ratio.
What is the C:N ratio?
Biodegradable rubbish from the kitchen and garden contains different amounts of carbon and nitrogen. For example grass is high in nitrogen whereas wood chips are very high in carbon. The amount of carbon and nitrogen in a material is known as the C:N ratio.
Note:
If your compost mix is too low in nitrogen, it will not heat up. If there is too much nitrogen the compost may become too hot, killing the tiny organisms that break it down.
The recommended C:N ratio at the start of the composting process is about 30/1 (30 lots of carbon to 1 lot of nitrogen).
How to work out the C:N ratio
To work out the C:N ratio of your rubbish you can use the chart below.
Example:
2 x bags of grass clippings (C: N = 20:1)
1 bag of leaves (C: N = 60:1)
Add the C: N ratios together then divide by the number of bags:
20:1 + 20:1 + 60:1 = 100:1 / 3 = 33.1
C: N ratio = 33:1
| Material | C:N Ratio |
| Coffee Grounds | 20:1 |
| Corn Stalk | 60:1 |
| Cow manure | 20:1 |
| Fruit Wastes | 35.1 |
| Grass Clippings | 20:1 |
| Horse Manure w/ Litter | 60:1 |
| Leaves | 60:1 |
| Newspaper | 50-200:1 |
| Oak Leaves (green) | 26:1 |
| Pine Needles | 60-110:1 |
| Rotted Manure | 20:1 |
| Sawdust/ Wood | 600:1 |
| Sawdust weathered for 2 months | 325:1 |
| Straw | 80-100:1 |
| Table Scraps | 15:1 |
| Vegetable Trimmings | 12-20:1 |
