ANR-850, Reprinted Jan 1996. James Donald, Extension Agricultural Engineer; John P. Blake, Extension Poultry Scientist; David Harkins, Extension Associate, Environmental Management; and Kevan Tucker, Extension Associate, Environmental Management

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Questions and Answers about Using Mini-Composters

What are the main differences between mini-composting and full-scale composting?

One difference between mini-composting and full-scale composting is in the equipment. Full-scale composting requires a tractor with loader for loading, turning, and removing large amounts of litter and compost whereas mini-composting requires manual labor to move small amounts of litter. Another difference is that full-scale composting requires a secondary bin for turning the compost. Mini-composting is a single-stage process that does not require turning.

What are some of the advantages of mini-composting over full-scale composting?

The major advantage of mini-composting over full-scale composting is cost. A mini-composter can be constructed for approximately 25 percent of the cost of a full-scale composter. In addition, front-end loading equipment is a major cost for full-scale composting. Such equipment is unnecessary for mini-composting. Another advantage is that less litter is required to operate a mini-composter than is required for a large-scale composter.

Why is turning the compost not necessary in mini-composting?

Turning the compost increases the air flow through the composting material. Mini-composters are constructed with spaces between side boards to allow air to flow easily through the material. The use of cake litter also helps to increase the air flow. These two factors make turning unnecessary.

What are the components of a mini-composting operation?

The components of a mini-composter are wooden boxes to hold dead poultry and other composting materials and a shed with a concrete slab. The 4 x 4 x 4 foot boxes are constructed from pressure-treated lumber with 1/2-inch air spaces between the side boards. The boxes are placed on concrete under a shed, which is separate from the poultry house. A shed ensures all-weather operation and controls the moisture content of the compost. Concrete prevents soil contamination, excludes vermin, and most importantly, provides an excellent working surface for manure-handling equipment.

How is the mini-composter operated?

The mini-composter is easily operated by an individual. First, place a 4- to 6-inch layer of litter on the concrete floor. If you are using straw, add it now. Next, place a layer of birds. When placing carcasses, be sure to keep them at least 6 to 8 inches away from the sidewalls of the bin. Cover the layer of carcasses with another 3- or 4-inch layer of litter. Repeat layers beginning with straw, then adding carcasses and litter. When the bin is full, cap the bin with a 6-inch layer of litter.

Should water be added?

Water is added to maintain a moist but not saturated condition. The use of cake litter may reduce or even eliminate the need to add water, depending on the moisture content of the cake itself. If it is necessary to use water, apply it to the cake. Add it only if you think the moisture content of the litter is insufficient.

Is the use of straw necessary?

Straw is used as a carbon source and as a passageway for air. If you use litter from a broiler house, it will contain wood shavings that should provide a sufficient amount of carbon. The mini-composter box is constructed with 1/2-inch spaces between the side boards. These spaces usually allow enough air flow. If you use caked litter, which does not pack down, straw is usually not necessary.

How do you monitor the mini-composting process?

Monitor the composter by checking the temperature of the material. A 20-inch probe-type thermometer is all you need. If the temperature readings are in excess of 135°F, then the composter is functioning properly. If the readings are below 135°F, then the ingredients are not generating enough heat to compost the carcasses. One reason for low temperatures is insufficient litter or cake moisture. Try adding a little more water, and wait a few days to see if the temperature increases. Another reason for low temperatures is not enough air flow. This could be caused by too much packing of the ingredients in the bin. Try adding a little straw, and be certain that you are using caked litter, which will not pack down easily.

Are flies a problem?

Fly breeding is not a problem in mini-composting provided the process is done properly. If proper moisture levels are maintained and carcasses are completely covered, flies will not be a problem.

How long does the mini-composting process take?

The mini-composting process is fairly rapid. If moisture content and temperatures are properly maintained, the process should be complete in 21 to 25 days after the bin is capped.

Will mini-composters handle larger carcasses?

Mini-composters are capable of handling larger carcasses. The composting process, however, may take 4 to 7 days longer. These larger carcasses are still broken down completely. Composting larger carcasses may require more boxes than would be needed for smaller carcasses.

Will mini-composters handle large die-offs?

Normal bird mortality for a 20,000-bird house can be handled by 4 to 5 mini-compost boxes. Larger die-offs would require other disposal methods.

What is the cost of construction?

Mini-composters are very inexpensive to construct. Costs range from $1,200 to $1,500 depending on the current price of lumber. This cost includes enough material for the bins, the shed, and the concrete floor.

Printed by the Alabama Cooperative Extension System in cooperation with the Alabama Department of Environmental Management and the Environmental Protection Agency with Clean Water Act Section 319 Demonstration Funds.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.