#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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