Composting

Master Composter Programs are designed to extend composting information to the public through volunteers who have successfully completed a comprehensive training program. Currently, Grays Harbor and Pacific Counties Master Gardeners do not provide a Master Composting Program however, our Master Gardeners are available to give advice on composting.

Below are four sets of home composter plans. Download and use these plans to set up your own home composting operation.

Cinder Block Composting

Garbage Can Composting

Wire Mesh Composting

Wood and Wire Bin Composting

Composting is a sustainable gardening technique that quickly recycles raw organic material. Soil microorganisms break down the organic material, releasing nutrients in a form that living plants may utilize. Adding compost to your garden is one of the best ways to improve your soil. It may be either incorporated directly into your garden soil or used as a surface mulch around individual plants or within beds.

Composting has many advantages:

It speeds up the recycling of raw organic material, releasing important nutrients.
It reduces the amount of garden waste that is either burned or dumped in landfills.
When incorporated into the soil, compost also improves the soil structure by aiding in water and nutrient storage, and by making the soil more porous and easier to dig.
When compost is applied to the surface as a mulch, it aids in regulating the soil temperature, reduces the number of weeds, and helps to maintain soil moisture.

Composting Methods

Fast (Hot) Composting.

This method balances the food, water and air in the compost pile so that the growth of thermophilic (heat-loving) microorganisms is encouraged. These thermophilic microorganisms cause the internal temperature of the compost pile to rise rapidly to 120 – 150 degrees F, killing most of the weed seeds and pathogens that may be in the compost. After the thermophilic microorganisms have finished, other soil organisms complete the decay process. If properly done, the compost produced by the fast method has substantially fewer weed seeds and plant pathogens.

Slow (Cool) Composting.

Slow composting resembles the natural process of decomposition seen in nature. In slow composting, raw woody materials are simply mixed together and left to slowly decay for a year or more. It does not encourage the growth of thermophilic microorganisms, and therefore does not generate sufficient heat within the compost pile to kill weed seeds or pathogens.

The Composting Environment

The speed of the composting process, and the quality of the compost produced, depends on several factors:

Raw Materials

The organic material composted may provide either energy or bulk, or a combination of these two properties.

Energy materials provide nitrogen and high-energy carbon components. These usually have a high moisture content, such as grass clippings, fresh manure, and garden trimmings. These materials are sometimes called the “green” materials.
Bulking agents help keep the compost pile aerated. These usually are dry, and include materials such as wood chips, dried grass hay, and sawdust. These materials are sometimes called the “brown” materials.
Balanced raw materials have both energy and bulking properties. These have low to medium moisture and include materials such as ground-up tree or shrub trimmings, horse manure with the bedding, and deciduous leaves.

A balance between energy and bulking materials will give the best results. A mixture of one part energy sources and two parts bulking materials is a good mix for fast composting.

Particle Size

Smaller particles have more surface area for soil organisms to work on. In general, the smaller the particle size, the faster the raw materials will be transformed into compost. To speed up the composting process, you should grind, cut, chop, or smash the raw materials to reduce the particle size.

Material Mixing

If you have all of the raw materials on hand when you start your compost pile, simply mix all of the materials together (there is no need to layer the raw materials). If you are adding raw materials to an existing compost pile, open the pile and add the raw materials to the center of the pile whenever possible.

Pile Size

Larger compost piles hold more heat and moisture than smaller piles, and create finished compost faster. A pile of one cubic yard in size will work well even in cold weather areas.

Moisture

The materials in the pile should be moist, but not soaking wet. During dry spells, you may want to moisten the pile contents with a garden hose when you turn it. During excessively wet weather, you may need to cover the compost pile with a tarp to prevent it from becoming water saturated.

Aeration

The microorganisms responsible for fast composting need oxygen. For this reason, the compost pile should be porous to air so that the oxygen within the pile may be replaced as it is consumed. Including bulking materials in your compost pile will aid in aeration, as will turning the pile occasionally and using porous bins to contain the compost pile. If oxygen cannot penetrate into the pile, the compost process will slow down and the pile may develop an unpleasant odor.

Microorganisms

The microorganisms necessary for the decomposition of organic material are already found on the raw materials you add to your compost pile, so there is no need to add soil or “compost starters”. While it is not necessary, if you wish to innoculate your pile with microorganisms, simply incorporate a small amount of finished compost into your new pile.

Nutrients

The microorganisms that break down plant material require nutrients to grow and thrive. The raw plant material in the pile usually provides all of the nutrients necessary. However, if your pile consists mainly of bulking agents (low in nitrogen), adding a small amount of nitrogen to the pile may benefit the microorganisms. Adding large amounts of extra fertilizer to your compost pile will not contribute to how well it functions.

Composting Containers and Bins

It is not necessary to have a container or bin to make compost. If you are using either the fast or slow method, a pile of the appropriate size and composition, turned occasionally to aerate the pile in hot composting, will make excellent compost.

Commercial or home-built composting containers and bins may also work well, especially if you have limited space or wish to continuously compost materials. These may have multiple chambers where compost in various stages, from raw material to finished compost, may be stored. Or the container or bin may have a single chamber where one pile of raw materials is composted at a time, all within a confined space. Composting containers or bins should be rugged, allow easy access to the pile, and allow for air penetration.

When is the Compost Done?

After the initial mixing, a new fast compost pile will heat up quickly, remaining hot for several weeks or a month. At this early stage, the internal heat will drop when you turn the pile but will quickly rise again due to the air and raw organic material which turning brought into the center of the pile. ……

…… By the end of this initial composting stage, the volume of material will have shrunk to about one half of its original volume, and the raw organic material in the pile will have been transformed into a crumbly, brown substance with few identifiable plant fragments.

Using uncured compost may harm some plants, so it is important for you to let your new compost cure completely. Let your uncured compost sit until at least eight weeks has past since the initial mixing, it does not rise in temperature when the pile is turned, and has become even darker in color. At this point, your compost is finished and may be used freely in your garden as a mulch or soil amendment.

Words of Caution

As mentioned earlier, slow composting does not reach the internal temperatures necessary to kill weed seeds and plant pathogens. Even fast composting, which is produced at much higher temperatures, does not kill all of the weed seeds and plant pathogens.

With this in mind, you should be selective about what plant materials you add to your compost pile. Do not compost material from diseased plants, for you may spread the disease around your garden when you eventually use the compost. Also avoid composting weeds that have gone to seed, for the seeds may survive the composting process and spread when the compost is used.

There is a slight chance that herbicides used in the garden will survive the composting process, eventually harming other plants when the finished compost is used. For example, such contamination may occur when grass clippings from a lawn that has been treated with a “weed and feed” product are added to a compost pile. If you suspect that herbicides may have contaminated your compost, let the compost sit unused for a year or more so the herbicides will have had time to break down.

Remember that some raw materials, such as fruit and vegetable waste and kitchen scraps, may attract pests. It is best to bury potentially attractive materials deep within the pile. If this is not successful in keeping pests away, you may need to either screen your pile or avoid composting these materials.

Resources

Gardening in Washington: Organic Gardening.
WSU Extension web site that offers many links to organic gardening topics.
Backyard Composting EB1784e.
WSU Extension bulletin with an explanation of the basic interactions of “fast” and “slow” composting, term definitions, and composting materials explained by moisture, porosity, and nitrogen content. Troubleshooting tips with health and safety information. Learn how to build and turn a pile, what NOT to add, and how to use your finished compost.
Composts and Nutrient Management.
WSU Puyallup Organic Farming Systems and Nutrient Management site with current research results considering the effects of compost applications on nitrogen availability and soil properties, useful composting, and publication links.
Cornell Composting.
Cornell University site with access to a variety of composting educational materials and programs.