Let’s talk about compost—what it is and why we need to make it happen now more than ever. Every time we eat plants or animals who eat plants, the nutrients they and we need to grow are taken from the soil and put into our bodies for energy. We burn it as energy, but there are always leftovers. Up to 40% of the food in the United States is wasted according to the Natural Resources Defense Council (2011). If these leftovers are not returned to the soil to be reborn (dust to dust), then the cycles that sustain life are broken and things start to get messy. You’ve probably heard this before, but it’s worth repeating. A handful of compost contains more living organisms than there are people on earth. Our eyes cannot see it, but compost is dynamically alive! The nutrients, minerals, bacteria, fungus, and other microscopic life forms found in compost are vital for healthy soil.
In the United States, we use soil 10 times faster than the natural rate of replenishment, and we only have about 60 years of topsoil left in the world . Such an estimate has to give us pause, and a dose of healthy concern. We need compost in all its forms—backyard piles, turned under cover crops, worm bins, municipal compost operations, forest floors, manure left in the field or composted in the barn, compost toilets (yes, human compost)—and every other way we can think of. We need to balance our soil withdrawals with compost deposits.
This can happen in your own backyard, in a church kitchen, in a community garden, in a garage, and even in an apartment. I’ll discuss how to make compost piles unique to your life style a bit later, but for now I’ll sum up what makes composting work no matter what form it takes. There are 5 keys to creating a healthy compost pile—carbon, nitrogen, water, air, and mass.
1. Carbon and nitrogen are the main ingredients of compost. Vibrant compost piles need a ratio of 20-35 parts carbon to 1 part nitrogen. Carbon, the “brown” materials, are usually brown and dry. Bags of fallen leaves, newspaper, cardboard boxes, paper towels and napkins, wood chips, straw, brown grass clippings, and the morning croissant are all examples of carbon. These are what the compost microorganisms need for sustained energy. Smaller pieces of brown material will break down more quickly because there is more surface area for the microorganisms to work on. Chipping wood or mowing leaves helps to speed up the composting process.
2. Nitrogen, the “green” materials, are usually green and wet. Fresh grass clippings, kitchen scraps, manure of all kinds, coffee grounds, and nutrients like blood and bone meal are all good sources of nitrogen. These will be used by the microorganisms to build their microscopic bodies.
3. A compost pile should be as wet as a wrung out sponge. In order to move, breathe, and function, the microorganisms doing all the work need this water.
4. The microorganisms that break down organic matter also need oxygen. You can compost without oxygen, but it’s smellier. This is called anaerobic composting (more on that later). Making sure the pile has plenty of brown, carbon material to create pockets of air will ensure it has enough oxygen. The pile should be a bit fluffy, like a compost soufflé. As it breaks down, the cake will flatten and reduce in size. This is a good sign.
5. The last key is mass. If it’s not big enough, the compost pile will not be active. A 3’ by 3’ pile is the minimum size for decomposition to really start. But piles built outside need to be at least knee high and wide. You can put your pile inside chicken wire, straw bales, re-used pallets, or even a cheap garbage can buried a foot in the ground with holes drilled into the bottom. More about compost containers later.