Carbon-to-Nitrogen Ratios
What to add and how much is key to reaching the perfect balance of brown and green materials in your compost bin or pile. Here’s the numbers.
Best product
for Hot Compost
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). For best performance, the compost pile, or more to the point the composting microorganisms, require the correct proportion of carbon for energy and nitrogen for protein production. Scientists (yes, there are compost scientists) have determined that the fastest way to produce fertile, sweet-smelling compost is to maintain a C:N ratio somewhere around 25 to 30 parts carbon to 1 part nitrogen, or 25-30:1. If the C:N ratio is too high (excess carbon), decomposition slows down. If the C:N ratio is too low (excess nitrogen) you will end up with a stinky pile.
Convert kitchen, yard and garden waste into soil-nourishing organic matter with our backyard tested composting bins and supplies. Decreasing household waste and building your soil has never been so easy!
Below are the average C:N ratios for some common organic materials found in the compost bin. For our purposes, the materials containing high amounts of carbon are considered “browns,” and materials containing high amounts of nitrogen are considered “greens.”
Estimated Carbon-to-Nitrogen Ratios |
|
| Browns = High Carbon | C:N |
| Ashes, wood | 25:1 |
| Cardboard, shredded | 350:1 |
| Corn stalks | 75:1 |
| Fruit waste | 35:1 |
| Leaves | 60:1 |
| Newspaper, shredded | 175:1 |
| Peanut shells | 35:1 |
| Pine needles | 80:1 |
| Sawdust | 325:1 |
| Straw | 75:1 |
| Wood chips | 400:1 |
| Greens = High Nitrogen | C:N |
| Alfalfa | 12:1 |
| Clover | 23:1 |
| Coffee grounds | 20:1 |
| Food waste | 20:1 |
| Garden waste | 30:1 |
| Grass clippings | 20:1 |
| Hay | 25:1 |
| Manures | 15:1 |
| Seaweed | 19:1 |
| Vegetable scraps | 25:1 |
| Weeds | 30:1 |
Note: Many ingredients used for composting do not have the ideal ratio of 25-30:1. As a result, most must be mixed to create “the perfect compost recipe.” High C:N ratios may be lowered by adding grass clippings or manures. Low C:N ratios may be raised by adding paper, dry leaves or wood chips.
Many home gardeners prefer to put up with a slight odor and keep some excess nitrogen in the pile, just to make sure there is always enough around to keep the pile “cooking!” Learn more about building a compost pile here.
Related Questions
-
What products to compost
Hello,
You will be able to source all of the essential elements in order to build a great compost pile without having to look too far! As long as your carbon to nitrogen ratio is optimal (25-30:1) your compost pile will be breaking down properly. Here are some lists of acceptable additions:
Carbon Rich Material "Browns"
Cardboard (free of dyes)
Corn stalks
Fruit waste
Leaves
Newspaper
Peat Moss
Saw dust
Stems & twigs
StrawNitrogen Rich Material "Greens"
Alfalfa/Clover/Hay
Algae
Coffee grounds
Kitchen food waste
Garden waste
Grass clippings
Hedge clippings
Manures
Vegetable scraps
Weeds (that have NOT gone to seed)​Things to Avoid
Meats
Bones
Fats/oils/grease
​Diseased plant material
Colored paper
Coal/charcoal
Cat/dog waste
Manures from carnivorous animals
Onions
Garlic
Citrus peelsAs for the rhododendron and holly leaves, you can definitely put them in your compost pile. However, it is a good idea to really chop or shred them up, as they take much longer to break down due to their fibrous and waxy make up. It really depends on how quickly you are trying to create usable compost. It might be a good idea to have a separate pile going that you incorporate those leaves into and another pile that you do not. That way you can have a pile you know will rapidly break down into garden goodness and have yet another ready to use later on. Good luck!
Recommended Products
Compost Starter
Includes the microbes needed to speed up the decomposition of raw organic materials.
$9.95Read more
Compost Thermometer
Keep your pile cooking with this 20-inch long, stainless steel thermometer.
$29.95Read more
Red Composting Worms
Red wigglers (Eisenia foetida) convert food waste into nutrient-rich castings.
$34.95Read more
European Nightcrawlers
European nightcrawlers are amongst the best options available for composting worms.
$43.94Read more
Compost Turner
An easy and effective way to mix and add oxygen to the pile without heavy lifting.
$29.95Read more
Bucket Screen Sifter
Sifts your chunky materials into a finely-blended nutrition cocktail for plants.
$19.95Read more
Copyright © 2004-2023