Backyard Compost

Organic material makes up about 58 percent of what Denver residents send to the landfill every year. These items can be composted, which is the controlled decomposition of organic materials by microorganisms. This process results in compost, a crumbly, earthy-smelling, nutrient-rich, soil-like material.

Compost contains both carbon and nitrogen sources, which can be simplified as browns for carbon (e.g., leaves, straw, woody materials) and greens for nitrogen (e.g., grass and food scraps). Adequate sources of carbon and nitrogen are important for microorganism growth and energy. 

Organic materials are broken down through the activities and appetites of various invertebrates that will naturally appear in compost, such as mites, millipedes, beetles, sowbugs, earwigs, earthworms, slugs, and snails. These microorganisms need adequate moisture and oxygen to degrade the organic materials in the most efficient manner. 

Microbes in the pile create considerable heat and essentially "cook" the compost. Temperatures between 90 and 140 degrees Fahrenheit are common in properly maintained compost piles, but may not reach these levels in backyard compost piles. These high temperatures are necessary for rapid composting as well as for destroying weed seeds, insect larvae, and potentially harmful bacteria. When the compost is finished, it has a crumbly texture throughout the pile. 

Vermicomposting is a method of composting that uses a container of food scraps and a special kind of earthworm known as a red wiggler. Over time, the food is replaced with worm droppings, a rich brown matter that serves as an excellent natural plant food.  For more information on what to feed worms and a list of worm vendors visit the page Bins for Home Composting.
  1. Choose a level area at least three feet square (3' by 3'). The area should receive only partial sun. The area can be fenced off, or you can use a pre-manufactured composting bin (list of bins for home composting). 
  2. Open the ground with a pitchfork or shovel approximately an inch or so under your pile area. This allows the soil microorganisms access to the food sources in your compost pile.
  3. Add an alternating mix of four-inch to six-inch layers of finely chopped high carbon and high nitrogen materials. 
  4. To introduce friendly microorganisms to your pile, throw a handful or garden soil on top of the layers. Mix the carbon and nitrogen layers with a garden fork.
  5. Water the layers until they feel like a wrung-out sponge.
  6. Continue building your layers of carbon and nitrogen materials, remembering to throw a handful of soil on top of each layer. Mix each new carbon and nitrogen layer before watering.
  7. Direct sunlight slows the composting process, so cover the top of your pile with black plastic or straw. This also keeps the pile from drying out and slows the loss of soluble nutrients.
  8. Once a week, turn or stir your pile to provide air channels. A spading fork or commerical aerating tool can help with this.
  9. Keep your carbon and nitrogen layers finely chopped, add a little soil, build the pile a minumum of three feet high, maintain the moisture so it's like a wrung-out sponge, and turn it for air. In just two months, you will have your own brown gold compost!

If you supply the proper conditions (volume, surface area, moisture, air and variety of materials), you should have little difficulty maintaining your compost system. Occasionally, though, problems occur in any biological system. They usually can be dealt with fairly easily by following these tips:

  • Odors - Odors can be caused by not supplying enough air to the mixture. Turning the pile can help. If the pile is too wet, turn the pile and add extra sources of coarse carbon, such as shredded twigs, alfalfa meal or straw. Of there is too much high nitrogen material, add extra sources of coarse carbon as above.
  • Pile doesn't heat - Typically, this is due to a lack of nitrogen material. Mix in high nitrogen sources, such as grass clippings or bloodmeal. The pile also may not be large enough to heat well. In this case, add more material until the pile is at least 3' x 3' x 3'.
  • Center of pile is dry - If the pile is dry, it is not getting enough water. Remember to moisten the pile as you build it.
  • Flies - Flies are attracted to decaying food scraps. Bury food scraps well within the compost pile. Food scraps may also be composted indoors using a ventilated worm box and redworms.

Compost is ready to use when it is dark and crumbly. You should not be able to recognize most of the materials, and it should smell like a damp forest floor.

  • For vegetables, flowers and herbs - Fork it lightly into the soil several times during the growing season. It will conserve moisture, open up air channels in the soil, and slowly release nutrients for your plants.
  • For trees and shrubs - After cultivating the soil at base of the plant, spread an inch or two of compost around the drip line. Leave the area surrounding the trunk free of compost to prevent mice from burrowing there in winter.
  • For lawns - Spread aged compost thinly over newly aerated grass. Eventually, it will help loosen clay soild and allow a healthier, deeper root structure for grass plants. Deeper roots allow plants longer time periods between watering.
  • For houseplants - Enrich potting soils by adding up to 20 percent finely screened compost. Make a good moisture retaining potting soil by mixing finely screened compost, sphagnum peat, and perlite.
For more information about composting, call Denver Recycles at 3-1-1. We can offer additional resources, and provide information about composting classes.

Denver Urban Gardens (DUG) sponsors free, hands-on composting classes at the Gove Community Garden, usually from mid-May through October. Call DUG at (303) 292-9900 to register, or visit their web site at 

www.dug.org. Also, Master Composter classes are offered on an annual basis. Sign-up usually begins in December and classes start in early March.

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