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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                                                                                                               110:1

Peanut shells                                                                                                                 35:1

Peat Moss                                                                                                                      58:1

Pine needles                                                                                                                  80:1

Printer Paper                                                                                                               129:1

Sawdust                                                                                                                       500:1

Straw                                                                                                                               75:1

Tissue Paper                                                                                                                  70:1

Wood chips                                                                                                                 500:1


Greens = High Nitrogen                                                                                  C:N

Alfalfa                                                                                                                              12:1

Ashes, wood                                                                                                                  25:1

Clover                                                                                                                             23:1

Coffee grounds                                                                                                             20:1

Fish Scraps                                                                                                                       5:1

Food waste                                                                                                                    20:1

Garden waste                                                                                                                30:1

Grass clippings                                                                                                             20:1

Hair / Fur                                                                                                                       10:1

Hay                                                                                                                                  25:1

Manure (chicken & poultry)                                                                                      10:1

Manure (cow)                                                                                                               20:1

Manure (horse)                                                                                                             25:1

Manure (pig)                                                                                                                   6:1

Manure (sheep)                                                                                                            20:1

Seaweed                                                                                                                          19:1

Vegetable scraps                                                                                                           25:1

Weeds                                                                                                                             20:1




This is not supposed to be an all inclusive list, but rather a basis to work from to figure out the carbon to nitrogen ratio of similar materials.


A higher nitrogen percentage in your compost pile will mean that it will be hotter, and compost faster, but it will also give off a slightly unpleasant odor. A higher carbon percentage in a compost pile will decompose slower at a cooler temperature and will not give off unpleasant odors, but is harder to keep "active". 


Many home gardeners prefer to put up with a slight odor from the pile and keep some excess nitrogen in the pile, just to make sure there is always enough around to keep the pile “cooking”. This method is also used by home gardeners to produce finished compost piles faster for use in their gardens in a matter of weeks instead of months.


You do not have to worry so much about the exact carbon to nitrogen ratio for your compost pile. Remember, if it is too difficult you will not do it, so keep it easy. Simply add about twice as much brown material as you add green. Remember, anything that was once living is made up of both carbon and nitrogen, and therefore it can be composted.


And yes, you can add bone and meat to a hot compost pile. Ignore the myths that say you cant add meat or dairy products to a compost. Meat and bones added in a hot compost actually add phosphorus to the compost which most plants material can not do. If you were to add a dead animal in a hot active compost pile, you would be surprised at how quickly it would completely disappear, being broken down into the compost. I was shocked the first time I saw it happen to a squirrel that wouldn't stay out of my garden.


I know at least one of you out there is wondering about composting a human body. And yes it is possible to compost a human body in a hot compost pile at home, but I am not going to divulge the carbon to nitrogen ratio to you and give you sick people any ideas. If you are so inclined and are wanting to know how to quickly get rid of your boss or your ex-wife, you can look that one up yourselves, lol.




Until Next Time,

Aloha & 73





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