Building a compost pile with layers of different raw materials is a technique based on solid science that will help you produce more desirable final compost. Alternating layers of high-carbon “browns” and high-nitrogen “greens” helps keep the preferred balance of carbon-to-nitrogen.
We build our compost pile starting with a base of high-carbon, highly-absorbent material, like leaves or sawdust, topped with finished compost or garden soil. The finished compost and soil provides some starter populations of our “compost critters,” microorganisms that will decompose the pile’s raw materials. We like using a high carbon base layer to define the bottom of the pile and soak up any water that drizzles down through the compost heap.
Building the next layers of the compost pile involves alternating greens and browns. This involves adding a little bit of math to the science of high-carbon browns and high-nitrogen greens. Most backyard composting recommendations suggest that you aim for a “carbon-to-nitrogen ratio” somewhere between 25:1 to 40:1. We use a lot of shredded leaves, and our leaves seem to decompose best when we estimate their carbon-to-nitrogen ratio around 60:1. That means we have to mix them with a high-nitrogen source (like our neighbor’s chicken litter, which is around 15:1) to achieve a proper mix in the pile.
We’ve found it works best to make a four-inch to six-inch layer of shredded leaves followed by either an inch or two of chicken litter or two to four inches of kitchen wastes, grass and plant trimmings. This adds enough nitrogen to heat up the pile and help decomposition increase, especially if the pile is turned. You will also want to sprinkle each layer with water, to add moisture needed by the bacteria that will do most of the work of composition.
Our area heavily wooded, and we collect oodles of shredded leaves each fall – too many, in fact, when we start our compost pile. So we stockpile some piles of leaves out of sight, at the edge of the woods, using them to “feed” a new compost pile when we build it in the spring. If left alone, these piles will also decompose into compost, but the process will take more than a year, closer to two years. That’s why we prefer to build a layered compost pile. Mixing the leaves in layers with higher-nitrogen yard and food wastes helps us more quickly make compost which may be used in our flower beds.