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#118 - Carbon to Nitrogen Ratios (C:N)

After uploading my last post I received an email asking about the carbon to nitrogen ratio of a few common items that people add to the home compost piles, so I thought I would upload a list of common compostable items along with their Carbon to Nitrogen ratios.


All organic matter is made up of substantial amounts of carbon (C) combined with lesser amounts of nitrogen (N). The balance of these two elements in an organism is called the carbon-to-nitrogen ratio (C:N ratio). 


Although we want to have an ideal balance of around 30:1 that does not mean that we want to have 30 times more brown material than green material. It all goes by the C:N ratio of each item.


Even green items which are considered high in nitrogen contain a higher ratio of carbon than nitrogen. Take for instance fresh green grass clippings. Everyone considers them to be "green" because they are full of nitrogen and we consider them a great source of nitrogen for the compost, yet the C:N ratio of fresh green grass clippings is actually about 20:1 so they actually have much more carbon in them than nitrogen.


Anything with less than about a 30:1 ratio is considered "green" and a good source of nitrogen. Anything higher than a 30:1 ratio is considered "brown" and is a good source of carbon.


Here is a handy list of common composting materials and its associated ratio:


Browns = High Carbon                                                                                    C:N


Cardboard, shredded                                                                                                350:1

Corn stalks                                                                                                                     75:1

Fresh Leaves                                                                                                                 37:1

Fruit waste                                                                                                                     35:1

Leaves, brown                                                                                                               60:1

Mushroom Compost                                                                                                   40:1

Newspaper, shredded                                                                                                175:1

Paper Towels