How Is Compost Made?

Compost is a productive fertilizer that enriches the soil.

Compost is a productive fertilizer that enriches the soil.

Composting turns common organic yard and kitchen wastes into a productive organic fertilizer that enriches soil in gardens and cropland. While there are several variants of composting, the basics are simple and require an average of just several minutes per week after starting. The keys to effective composting are air, water and the right mix of ingredients to maintain a good biochemical balance in the compost pile.

Select a composting site. The location should be naturally flat and dry (sheltered from both standing water and rain) and shady. Pick a site far enough away from your house or woodpile to reduce the risk of bugs or rodents going where they shouldn't -- 30 feet is a good minimum distance. Keep the site within reach of a hose for when you need to moisten the compost pile.

Select a composting bin. While in principle, compost piles can be left open and uncontained, a bin will help keep the pile orderly, safer from animals and easier to manage. Whichever bin you select should keep the compost materials secure and allow adequate airflow, especially at the bottom.

Gather and prepare your compost materials. A good compost pile contains a mix of items that are high in nitrogen (grasses, weeds, plants, vegetable waste, coffee grounds) and high in carbon (leaves, wood chips, sawdust, shredded cardboard, newspaper). High-nitrogen items are often called "greens," while high-carbon items are "browns." Break any bulky materials or chunks into smaller pieces to speed decomposition. The target ratio of carbon to nitrogen in the compost pile is about 30 to 1. Consult a composting expert or online resource to check the specific carbon and nitrogen contents of the materials you're using.

Filter out items that shouldn't be there. If using kitchen waste, make sure you've removed any dairy items, meat, bones, whole eggs, grease and oils. These can create a foul odor and attract rodents. Keep human or pet wastes out of the compost pile; they can contain harmful bacteria, parasites and bugs. Any plants that are diseased or bug-infested must also be left out; bugs and diseases may survive the composting process, then go on to infect new plants.

Add the waste materials and form the pile. Add the "browns" and "greens" in thin layers of 3 to 6 inches, lightly wetting each layer as you add it, if dry. Try to make your bottom layer "brown" and lightweight (such as dead leaves) to help air circulate to the center of the pile. A few thin sprinklings of garden soil or topsoil between layers will help composting bacteria get started faster.

Turn the pile weekly and monitor it. Use a pitchfork to poke holes and turn the compost pile inside-out once per week. This keeps air and bacteria circulating. Check your pile at each turning interval. If the pile seems too dry, add water in moderation. By contrast, a "slimy" looking pile needs less water. Adding more "browns" can help dry a pile. A sour or "vinegar" smell indicates that the pile needs more air and turning. A happily composting pile will gradually shrink, brown and start to emit a fair-smelling, "earthy" odor.

Harvest your compost. After one to two months, you should have a pile of cool, crumbly, earthy, sweet-smelling material that's ready for work. Add or dig in a thin layer of the compost into your garden, and watch your plants grow.

Items you will need

  • Composting site
  • Composting bin (optional)
  • Organic yard and kitchen waste
  • Pitchfork or turning tool

Tips

  • Greasy and fatty items do not decompose well in a compost pile and may delay the composting process.
  • A compost thermometer can give you a good read on your pile's internal temperature. The center of the compost pile should be between 100 and 140 degrees Fahrenheit.

Warning

  • Pet manure must never be included in a compost pile.

About the Author

Aaron Zvi has been a writer and photojournalist for 10 years in Washington, D.C., and the Middle East. A student of political science and psychology from the University of Maryland, he also does technical and market analysis for a green technology company. His work has appeared in local newspapers, commissioned research and a patent or two. He began writing professionally in 1998.

Photo Credits

  • Justin Sullivan/Getty Images News/Getty Images