The wrong blend of compost ingredients will produce some pretty wicked sites and smells.
We don’t want you to make this mistake, so we’re going to teach you what to compost, as well as what not to compost. We’re also going to help you decide which materials to mix together, in the proper ratios, to create that rich black soil.
All Great Composters Understand This Ratio
Before we get to the lists of specific materials, we want to teach you about something called the composting carbon nitrogen ratio (C:N); or as some people think of it, the brown to green ratio. This concept is especially important to understand if you are going to be using materials that are completely dry (e.g. straw, newspaper, dried manure).
The C:N describes the proportions of various materials (e.g. food scraps and newspaper) that you’re going to be mixing together in your compost pile to create your finished product.
Ideal C:N = 20:1 – 40:1*
*These ratios are based on weight of the materials.
If you’re new to composting, please don’t get too caught up in these numbers. Trying to do all the math calculations can be quite frustrating. Instead, focus your attention on making sure your pile has a greater amount of carbon containing material than it does nitrogen containing material. For instance, if you add a lot of freshly cut grass (high nitrogen and moisture content) to your pile, you’ll also want to add some newspaper clippings (very high carbon content and minimal moisture).
Okay, let’s move on to the specific compost ingredients.
Common Sources of Carbon-Containing Ingredients
|dried grass clippings||50:1|
* newspaper must be black and white, and printed with 100% vegetable oil-based ink (e.g. soy). Please do not put colored papers into your compost pile.
** please read our notes below that refer to the use of pine needles in your compost.
Common Sources of Nitrogen-Containing Ingredients
|fresh grass clippings||15:1|
|freshly cut hay||25:1|
* weeds must be free of seeds.
Another interesting source of compost ingredients comes from the cotton industry. If you live in the Mississippi area, more specifically the Delta region, you probably know all about this product. Once composted it is often referred to as Cotton Burr Compost. This product offers many benefits, including increasing microbial activity, nutrient levels, and soil structure.
Eggs shells are a great compost ingredient; however, you’ll find that they break down a lot faster if you crush them, before you add them to your pile.
What NOT to Compost
|human feces**||pet waste**|
|large wood pieces||pine needles*|
|waxed cardboard||colored newspaper|
|oak leaves*||weed seeds|
|grease or oil||meats|
|animal carcases||pesticide treated plant waste|
* small amounts of pine needles and oak leaves are fine to add to your compost pile; however, avoid adding them in large amounts. These specific compost ingredients tend to break down more slowly than other materials in your pile. They also influence the pH of your pile when added in large quantities.
** for more information on composting human manure and pet wastes, please visit our composting toilet page.
Let’s Put it All Together
Now that you know what to compost and what not to compost, we suggest the following…
Figure out what compost ingredients you have on hand, and what materials you can get for free from your neighbors. Then use the above charts to determine the composting carbon nitrogen ratios of each material. Please don’t stress out by trying to find the perfect ratios.
As long as you have some materials with a low C:N, mixed with some materials with a high C:N, you should be off to a good start. For instance, if you have a wheelbarrow full of kitchen scraps (20:1), you’ll want to add about 3/4 of a wheelbarrow of dry leaves (70:1) to help balance it out.
Finally, refer to our how to make compost page to start building your compost pile.