What is composting?


Compost is simply rich, organic soil that is made as micro-organisms decompose yard and kitchen waste.  It can make grass greener, tomatoes bigger, and bushes bushier.  Compost can replace some fertilizer and reduce the amount of water a yard needs because it adds nutrients and increases the water-holding capacity of soil.

There are other methods of composting, for this section we will focus on the most common, composting with bins. Click here for composting with chickens or Bokashi composting.

What can I compost?

Anything that was a plant can be composted.  All plant materials contain nitrogen and carbon.  Materials high in nitrogen are called “greens” (grass clippings, manure, and kitchen scraps).  Materials high in carbon are called “browns” (leaves, sawdust, and wood chips). 

Most food waste can be composted. But you should avoid grease, fat, bones, fish, and meat scraps because these materials attract animals like dogs and often develop odors while composting.

Do not use diseased vegetable or flower plants for composting.  These diseases may be returned to the garden with the compost.

Before adding materials to the compost bin, chip or shred items so they are no more than 2-3 inches long. This will help these materials break down faster.  Do not compost charcoal ashes, sick or diseased plants, or treated wood and weedy plants, especially the roots.

Click here to see city of Phoenix’s Backyard Composting Guide.

Where should I locate my compost pile?

You can compost anywhere that’s convenient.  A shaded, well-drained spot may be best because partial shade keeps the pile from drying out and good drainage keeps water from collecting under the pile.  Consider a spot that is close both to a water source and the places where you’ll be using the compost.  Do not place the pile adjoining a wooden fence, deck, or building as it will cause these structures to rot over time.  Avoid slopes that drain to surface water or locations near wells and avoid placing your pile under acid-producing trees such as pines.

There are four things your compost bin needs:

  1. Carbon producing material: This category includes branches, twigs, and dead leaves. It is also called the brown category.
  2. Nitrogen producing material: Also called the green category, this includes organic table scraps and grass clippings.
  3. Water: Water helps aid in the decomposition of these materials.
  4. Oxygen: To speed up the process, turn the compost periodically.  You can do this by turning the material into another pile or by moving the materials from the outer sides to the center. 

How do you control odor?

There is an easy fix to odors in your compost.  Odors occur when not enough air (oxygen) is present in the materials. This can be prevented by incorporating more brown material and thoroughly mixing or turning the compost materials, which allows more air into the material.

When is composting ready to use?

The compost is finished composting and ready to use when it has a uniform look (like soil): dark color, small particle size, and “earthy” odor.  Most of the materials you put in will no longer be recognizable.  It will take about two months to generate your first batch of compost, depending upon how much work goes into it. You may want to remove large materials that have not yet decomposed and throw them back into the bin. Use finished compost as a mulch, soil amendment, or potting soil. 

Where can I get a compost bin?

You can buy a bin online; many cities offer damaged trash cans as compost bins for free or for a small fee.  Click here to get more info on city of Phoenix’s composter or click here to watch a video on building your own composter with wooden pallets.  

Benefits of composting

  • Incorporating compost into the soil can help to increase the soil’s ability to retain moisture and reduce the need for fertilizers, herbicide or fungicide on farms, gardens and landscaping.
  • Improves the soil structure, porosity, and density, thus creating a better plant root environment.
  • Increases moisture infiltration and permeability of heavy soils, thus reducing erosion and runoff.
  • Improves water-holding capacity, thus reducing water loss and leaching in sandy soils.
  • Supplies a variety of macro- and micro nutrients.
  • May control or suppress certain soil-borne plant pathogens.
  • Supplies significant quantities of organic matter.

Did You Know?

Composting can be as simple as making a pile of leaves and letting them sit until it decomposes

Compost aids in erosion control, promotes soil fertility, and stimulates development of healthy roots.

By composting, a typical household can reuse more than 500 pounds of  waste each year.

Do not use diseased vegetable or flower plants for composting.  These diseases may be returned to the garden.