Large-scale Composting Overview

Large-scale compost production includes municipal and commercial facilities composting high volumes of yard materials and/or food scraps, along with on-farm composting of these materials and animal manure.

In the most common type of large-scale composting, the compostable materials are usually placed directly on the ground in orderly rows ("windrows"). The material is turned periodically to mix and aerate it. Aeration helps the microorganisms digest the materials and eventually produce "finished" compost. For more about compost quality, see the Compost Quality and Marketing page.

Other types of large-scale composting include:

• Static rows or piles that are aerated using perforated tubes or blowers instead of turning.
• "In-vessel" composting that uses a continuously turning vessel and blower to provide aeration in a building or other facility, a method used to compost sludge or mixed solid waste in addition to yard waste.
• Vermiculture (composting using worms), which can be done on a small (home) scale or large scale.

How Much Land?

Seven acres is the approximate smallest possible area needed for a 20,000-cubic-yard windrow composting facility. (There are additional regulations for facilities larger than this.) This estimate assumes the finished compost is produced in one year or less and rapidly moved off site. A much larger area would be needed if the materials were turned only infrequently or if portions of the property were unsuitable for the composting operation. It is important to follow state regulations on the siting of large-scale composting facilities [PDF 83KB] to protect surface and groundwater from contamination and avoid other potential hazards and nuisances.

Factors to Consider

Important factors in the composting process include:

• temperature;
• the ratio of carbon to nitrogen in compostable materials;
• the pH of compostable materials;
• moisture content; and
• oxygen content or concentration.

See the other pages in this section for additional information and links to more resources for large-scale composting.