University of Missouri Extension

G6957, Reviewed October 1993

How to Build a Compost Bin

Composting is a natural biological process where bacteria, fungi and other organisms decompose organic materials such as leaves, grass clippings, and food wastes. The end product is called compost. While composting occurs naturally, the process can be accelerated and improved by human intervention.

Selecting a compost method

Methods

Compost can be made by five different methods: holding units, turning units, heaps, soil incorporation, and worm composting. The method of composting selected will depend on when finished compost is desired, the materials to be composted, and the space available for composting.

Alternatives to composting

Remember, many organic materials such as leaves, grass clippings and chipped branches can be used as a mulch Mulches placed on the soil surface control weeds, reduce evaporation, make soil temperature cooler in summer and warmer in winter, and reduce soil erosion.

In addition, grass clippings do not need to be collected for composting. Grass clippings will filter down to the soil and rapidly decompose if you mow frequently, fertilize properly and remove no more than one-third of the leaf blade.

Holding unit
Containers or bins that hold yard and garden materials until composting is complete. Allow 6 months to 2 years for finished without turning. Wire mesh (Figure 1) Snow fence (Figure 2)

Easy to build and least labor intensive. Good for small compost amounts of yard wastes. Slowest way to compost.

Turning unit
A series of bins or a rotating bin that allows organic material to be turned on a regular schedule.Two general forms: either a series of bins, as shown in Figure 3a, or a horizontally mounted rotating barrel, as shown in Figure 4.

With a substantial input of labor, a large volume of yard waste can be composted in a relatively short time (3 weeks to 6 months). Turning bins can require a greater expense to buy or effort to build.

A rotating barrel Figure 4
A rotating barrel composter.
 

Worm composting
Food wastes can be digested by red worms (red wigglers) placed in a bin with shredded and moistened newspaper, corrugated cardboard, peatmoss or sawdust. Requires temperatures between 50 and 70 degrees Fahrenheit so a basement or semi-heated indoor space is required. Worm bin (Figure 5a)

Small amounts of worms turn fruit and vegetable scraps into a high-quality soil amendment. Generally, every pound of food waste to be composted per week will require 1 square foot of surface area. Two pounds of worms are needed for every pound of garbage produced per day.

Heaps
No structure is required for heap composting. The pile should be at least 3 feet high and 3 feet wide; its length will vary depending upon the amount of material used. Heaps (Figure 6)

Least expensive way to compost as no physical structure is needed. Heaps may not appear as neat and tidy as using a bin(s) for composting. Composting will be faster if the heap is turned regularly.

Soil incorporation
Non-fatty food wastes can be buried at least 8 inches below ground level. Burying at least 8 inches discourages animals from digging up the waste. Soil incorporation (Figure 7)

Good method for disposing of small amounts of food wastes. Mix soil with the food waste to hasten decomposition. Wastes break down in one month to one year depending on soil temperatures, number of organisms in soil, and the carbon content of the wastes. Do not bury meat, bones or other fatty materials as it may attract pests.

Wire-mesh holding unit

A wire-mesh holding unit Figure 1
A wire-mesh holding unit.
 

A wire-mesh holding unit is inexpensive and easy to build out of either galvanized chicken wire or hardware cloth. Non-galvanized chicken wire also can be used, but it will not last as long. Posts provide more stability for a chicken-wire bin, but make the bin difficult to move. A wire-mesh bin made without posts is easy to lift and provides access to finished compost at the bottom of the pile while the compost at the top of the pile is still decomposing.

Materials

Tools

To build a wire-mesh unit with chicken wire

To build a wire-mesh unit with hardware cloth

Snow-fence holding unit

A snow-fence holding unit. Figure 2
A snow-fence holding unit.
 

A snow-fence holding unit is simple to make. It works best with four posts pounded into the ground for support.

Materials

Tools

To build a snow-fence holding unit

Wood and wire three-bin turning unit

A wood and wire three-bin turning unit. Figure 3
A wood and wire three-bin turning unit.
 

A wood and wire three-bin turning unit can be used to quickly compost large amounts of yard, garden and kitchen wastes. Although relatively expensive to build, it is sturdy, attractive and should last a long time. Construction requires basic carpentry skills and tools.

Materials

Materials for optional lids

Tools

To build a wood and wire three-bin system

Worm composting bin

A worm composting bin
Figure 5
A worm composting bin.
 

Worm composting is suitable for composting fruit and vegetable scraps. The worms eat kitchen scraps, turning the material into valuable organic matter.

Materials

Tools

To build a worm composting bin

Adding the worms
Moisten the bedding material by placing it in a 5-gallon bucket and adding water to achieve a 75 percent water content, by weight. Weight the dry material and multiply the weight by three to determine the weight of the water to add. If the material cannot be weighed, or if it is already wet, add enough water to dampen all the bedding. Excess moisture will drain off most materials when they are placed into the composting bin; however, peat moss may hold too much water.

It is a good idea to put wet bedding material into the bin outdoors and wait until all the water has drained out (one to two hours) before setting the bin up indoors. Add about 8 inches of moistened bedding to the bottom of the bin. Place the worms on top of the bedding, and leave the lid off for a while. The worms will work down into the bedding, away from the light.

Adding your wastes
Dig a small hole in the bedding and add your vegetable and fruit scraps. Then cover the hole with bedding. Small amounts of meat scraps can be added in the same way. Do not add any inorganic or potentially hazardous materials, such as chemicals, glass, metal, or plastic.

Maintaining your worm composting bin
Keep your compost pile moist, but not wet. If flies are a problem, place more bedding material over the wastes, or place a sheet of plastic over the bedding. As an alternative, try placing some flypaper inside the lid. Every three to six months, move the compost to one side of the bin, and add new bedding to the empty half. At these times, add food wastes to the new bedding only. Within one month, the worms will crawl over to the new bedding and the finished compost on the "old" side can be harvested. New bedding can then be added to the "old" side.

Heap composting

Heap Figure 6
The width and height of a compost heap — the length can vary according to the materials available.
 

Heap composting is similar to turning-unit and holding-unit composting except that it does not require a structure (Figure 6). The heap should measure about 5 feet wide and 3 feet high; its length will vary depending upon the amount of materials used.

The pile may be turned regularly or not at all. If the heap will be turned, vegetable and fruit scraps can be added (check with local authorities for ordinances that may be in effect for composting). If the pile will not be turned, adding vegetative waste may attract pests.

Incorporation

Incorporating food wastes into the soil well below ground surface is the simplest method for composting non-fatty food wastes. With time, the wastes will break down to fertilize established or future plantings. The wastes will decompose in one month to one year, depending on the soil temperature, the number of organisms in the soil, and the carbon content of the wastes.

Non-fatty food wastes can be incorporated outside the drip line of trees or shrubs, or buried in areas that are not being used to grow plants. The hole must be large enough to allow the waste to be buried under at least 8 inches of soil. Burying to this depth discourages animals from digging up the waste.

Chopped food wastes should be mixed into the soil before they are buried. Care must be taken to avoid damaging large roots when digging near trees and shrubs. Incorporation of meat, bones, or other fatty food wastes are not recommended as they may attract pests.

Soil incorporation Figure 7
Soil incorporation is a useful composting technique if you need to dispose of small amounts of food waste. Waste is mixed with soil to speed decomposition and covered with at least 8 inches of additional soil.
 

Published with permission from the Northeast Regional Agricultural Engineering Service, Ithaca, N.Y. 14853.
607-255-7654
G6957 How to Build a Compost Bin | University of Missouri Extension

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