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Get to Know Your Organic Materials: C:N Ratio Tables for Effective Composting

In our guide to the Carbon: Nitrogen ratio, we took an in-depth look at the role of the essential nutrients in composting. 

As discussed there, you CAN compost with a wide range of C: N ratios. 

Moreover, while you can calculate exact ratios, it’s complex, time-consuming and probably far more involved than the average home composter needs to worry about. 

Sometimes even finding the C:N ratio of different materials can be challenging.

When you DO find them, sources can disagree, as you can tell from the table on manure below!

At the same time, if you are a keen composter, it is handy to have a rough idea of the C: N ratio of different materials.

So, using various sources, I’ve compiled a table showing the C: N ratios of common organic materials. I hope you find it useful!

Carbon: Nitrogen ratios for food waste

Organic Material C:N RatioSource
Cocoa shells22:1On-Farm Composting Handbook
Coffee Grounds20:1On-Farm Composting Handbook
Corn cobs56:1 -123:1
(Average: 98:1 
On-Farm Composting Handbook
Food waste14:1 -16:1On-Farm Composting Handbook
Fruit waste15:1 – 35:1Pavlis, Compost Science
Poultry carcasses5-1On-Farm Composting Handbook
Vegetable produce19:1On-Farm Composting Handbook
Vegetable waste11:1 to 13:1On-Farm Composting Handbook

Carbon: Nitrogen ratios for grasses, straws and hays

Organic Material C:N RatioSource
Alfalfa pellets15:1Pavlis, Compost Science
General straw48:1-150:1Average: 80On-Farm Composting Handbook
Oat straw48:1-98:1On-Farm Composting Handbook
Wheat straw100:1-150:1On-Farm Composting Handbook
Legume hay15:1-19:1Average: 16On-Farm Composting Handbook
Rye grass30:1LibreTexts
Grass Clippings9:1-25:1
On-Farm Composting Handbook

Carbon: Nitrogen ratios for woody materials

Organic Material C:N RatioSource
Paper from domestic use127-178On-Farm Composting Handbook
Fir bark540:1LibreTexts
Hardwood bark116:1 – 436:1On-Farm Composting Handbook
Softwood bark131:1-1,285:1On-Farm Composting Handbook
Redwood sawdust1020:1LibreTexts
Corrugated cardboard563:1On-Farm Composting Handbook
Sawdust200:1-750:1On-Farm Composting Handbook
Shrub trimmings53:1On-Farm Composting Handbook

Carbon: Nitrogen ratios for manures

ManureC: N Ratio
(Modern Farmer)
C: N Ratio Average
(On Farm Handbook) 
Humanure10:16:1 – 10:1
Poultry7:16:1 (for laying hens)

Carbon: Nitrogen ratios for other organic materials

Organic Material C:N RatioSource
Blood meal3:1Pavlis, Compost Science
Fresh weeds10:1 – 30:1Pavlis, Compost Science
Leaves40:1-80:1On-Farm Composting Handbook
Oak leaves26:1Compost Fundamentals
Peat moss58:1Compost Fundamentals
Pine needles60:1 to 110:1Compost Fundamentals
Seaweed5:1-27:1On-Farm Composting Handbook
Yard waste30:1Pavlis, Compost Science

Wrapping up

Before finishing, I think it’s worth noting that ratios can vary from source to source. 

What’s more, the final ratio can vary on many factors. 

For example, if you are pulling weeds out, it might depend on how much soil is clinging to the roots. 

If you are cleaning out animal droppings, it’s going to depend on the bedding material you use.

So while these are handy as a rough guide, it’s difficult to be exact when it comes to adding C: N ratios. 

The key here is don’t worry too much – get it roughly right, and you’ll still get great compost.


On-Farm Composting Handbook Appendix A: Table A.1
LibreTexts: Carbon/Nitrogen Ratio
Washington State University: Compost Fundamentals
Modern Farmer: Get a Load of Our Manure Guide
Robert Pavlis, 2023, Compost Science for Gardeners

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