The primary method of backyard composting is aerobic composting which requires once a week turning and watering. The majority of commercial units employ this method of composting. However, another method of small scale composting involves anaerobic digestion. This method requires only final aeration before being used for gardening.

Organic material is formed into open piles or contained in composting bins that can be built or purchased in a variety of design types and materials. A more intensive system for institutions might include a paved area for heavy equipment maneuvering and multiple bins to allow for continuous composting.

A balanced compost mixture should contain approximately 25-30 parts carbon-rich materials such as leaves, wood waste, sawdust, and straw and one part nitrogen-rich materials such as grass clippings and food waste. Food waste will tend to attract scavengers, but burying it a foot below the surface of the pile will eliminate this problem. Meat, oil, or animal products should not be added to backyard compost since they will produce an unpleasant odor and attract animals.

For quicker and more homogenous compost, materials should be shredded, chopped, or chipped. However, particles should not be too small since the mixture needs to allow air to penetrate. A home or landscaping quality chipper can be bought or rented for occasional use. These machines will allow the inclusion of woody branches. These branches should be shredded prior to being included in a backyard pile, or it will take the branches much longer to decompose. In addition, these shredders will shred all material into a fine mulch that can be used directly in landscaping, or that will decompose in a few weeks/months into a fine soil amendment.

For backyard aerobic composting, a single pile should not exceed two cubic yards or it will be difficult to turn. If a front end loader is available for institutional composting, the piles can be larger. The piles should be watered and turned at least once a week for the first few weeks to produce compost in about one to two months. A well-aerated and well-mixed compost pile will smell clean and woodsy. Compost can be used when it is a rich dark brown color, individual particles are not distinguishable, and it is no longer producing heat.

States and/or localities may have additional regulations on composting which should be followed. The use of a front-end loader will increase fuels on site which may increase a facility’s need to comply with SARA (40 CFR 355 and EO 12856) reporting requirements and SPCC (40 CFR 112) issues. In addition, composting increases water use at a facility. Under EO 12902, federal facilities are required implement water conservation projects. CPG (60 FR 21370) states that in order to assist in compliance with Comprehensive Procurement Guidelines for yard trimmings compost, facilities can use compost generated rather than purchasing other soil amendments.

The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.

Consult the base safety office on proper personal protection equipment (PPE) and training prior to using mechanized equipment.

• Compost reduces the amount of waste to be disposed. Complete recovery of yard waste will reduce the amount of waste generated by an average of 15.9% while the addition of food waste will divert another 6.7% (U.S. EPA, 1994).
• Backyard or single facility composting incurs few costs for processing.
• No pick-up mechanisms or transport are required.
• Backyard composting is easily implemented and requires low technology.
• Backyard composting produces a nutrient-rich soil amendment for home gardening and landscaping.

• Composting potential to produce odors or attract pests.

Assumptions:

• Annual costs are "per household."
• Process 0.5 ton/yr. of yard waste and some food wastes.
• Produce 0.4 ton/yr. of finished compost.
• Composting bins : $50/ea
• Solid waste disposal costs: $13/ton
• Avoided topsoil purchases: $50/ton
• No labor requirements.

Economic Analysis Summary

Annual Savings for Diversion Method over Disposal: $27
Capital Cost for Diversion Equipment/Process: $50
Payback Period for Investment in Equipment/Process: < 2 years

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