Backyard Composting

— Written By

Woman moving composting materials with pitchfork

(Taken from the NC State Extension Publication “Backyard Composting of Yard, Garden, and Food Discards”)

 What is Composting?

Composting is the controlled decomposition of organic materials into a soil-like substance called compost. Home composting is an easy and economical way for individuals to convert their organic waste into a soil amendment that they can use to mulch landscaping, enhance plant growth, enrich topsoil, and provide other benefits to plants and soil.

What can go into Compost?

Organic materials that can be composted are commonly characterized as “browns” and “greens.” Browns are sugar-rich carbon sources (carbonaceous) that provide energy to microorganisms, absorb excess moisture, and provide structure to your pile. Browns include dead fallen leaves, newspaper, straw, sawdust, napkins, cardboard, twigs, hay, dryer lint, and bark. Greens are protein-rich nitrogen sources (nitrogenous) that provide moisture to microorganisms. Greens include grass clippings, vegetables and fruit, coffee grounds, tea leaves, livestock manures, and alfalfa.

Some materials may pose a health hazard or create a nuisance and therefore should not be used to make compost. Some of these products might include:

  • Dog or cat feces, litter, or dirty diapers (may contain parasites and pathogens)
  • Meat, fish, bones, fats, grease, lard, oils, eggs, or dairy products, such as butter, milk, yogurt, and sour cream (may create odors, attract rodents and flies)
  • Diseased or insect-infested plants (diseases and insects may survive and be transferred to other plants)
  • Weeds that have gone to seed and weeds with invasive roots, such as alligatorweed or bermudagrass

Compost Construction

Set up your compost pile or bin in a convenient location and place it in a shaded area within reach of a garden hose. The location should be a flat, open space that is protected from flooding or runoff to surface waters or wells. Keep the areas in front of and above the pile or bin clear so you can work without difficulty.

You do not need to use a bin to compost. Some choose to use a bin to keep the pile neat, help retain heat and moisture, or because they live in a neighborhood where a bin would be more appropriate than an open pile. For more information on bin construction visit the Extension Gardener Handbook.

Build your compost pile three to five feet high and at least three feet in diameter so it can become self-insulating to retain heat. Add four or five inches of carbonaceous materials (browns), then two or three inches of nitrogenous materials (greens), and keep alternating the layers. Another method is to thoroughly mix up browns and greens during loading. Be sure to thoroughly water each layer to ensure even moisture distribution. Toss in a handful of soil on each layer to introduce more microorganisms. Top the pile with four or five inches of carbonaceous materials to prevent flies and other pests and provide a filter for odors.

For a simple compost recipe, combine leaves, grass, food scraps, and coffee grounds at a 2-to-1 ratio mixture of browns and greens. To help get your compost pile hot, dust small amounts of one or more of the following (in meal form) on top of your greens: alfalfa, bone, hoof, soybean, canola, cottonseed, or blood. Adding a mixture of water and molasses, sugar, syrups, or flat soft drinks also helps to activate your compost pile.

Compost Maintenance

Compost piles produce heat as microorganisms feed on waste. Pile temperatures must exceed 131°F to kill most pathogens harmful to humans and pets, and they must surpass 145°F to destroy most weed seeds. A pile temperature that climbs to 160˚F, however, can kill decomposers and slow the composting process. Temperatures will be hottest in the center of the pile, and they will be cooler on the outer edges. If the pile does not heat adequately, it may be too small, there may not be enough oxygen or nitrogen, or it may be too dry or too wet. Turn the pile when the center begins to feel cool to the touch. Turning the pile helps revive the heating process by introducing oxygen and undecomposed material into the center.

When heating ceases, cover the pile with a fabric weed barrier and let it cure for six to twelve weeks. During that time, mist the compost to keep it slightly damp and poke it occasionally to let air in. Compost is basically ready to use when you cannot recognize the original materials, the pile temperature is less than 10 degrees warmer than ambient, it is dark brown or black, and it smells earthy (not like ammonia or rotten eggs). To make sure the compost is fully mature and stable, test it on radish seeds to make sure it does not prevent germination or damage the plants.

Compost Uses

Potted plants, garden and field crops, lawns, shrubs, and trees can benefit from compost. In clay soils, compost improves aeration and drainage, and makes it easier to work with hand tools. In sandy soils, compost increases water-holding capacity and increases soil aggregation. Compost may suppress some plant diseases and pests, and it encourages healthy root systems. Although compost contains macro- and micronutrients, it is often not enough to supply all plants’ needs. Thus, you should have your lawn and garden soils tested and fertilize accordingly. For information on soil testing, you can visit the North Carolina Department of Agriculture & Consumer Services Agronomic Services or you can contact Daniel Simpson at the N.C. Cooperative Extension of Pamlico County office at 252-745-4121 or daniel_simpson@ncsu.edu.