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A key to successful composting is dynamic management that promotes rapid decomposition.

March 31, 2014

4 Min Read

Successful composting can be tricky but with the right tool, you can have improved results. Compost is a mixture of organic materials undergoing aerobic biological decomposition. These materials are mixed, piled and perhaps moistened to maximize that decomposition. The finished compost is a carbon-rich product, sometimes called humus. Its nutrients are readily available for release into the soil for plant uptake.

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A successful composting process is an active process resulting in rapid decomposition under mostly aerobic conditions. The more active the composting process, the faster the process will reach completion. The term "stable" is often used to describe the nutrients in finished compost. Good compost will not tie up nitrogen in the soil nor inhibit the growth of plants. Active composting minimizes greenhouse gas production and odors, and effectively destroys pathogens. A key to successful composting is dynamic management that promotes rapid decomposition.

Managing the composting process begins with a good compost recipe consisting of the right ingredients in the right proportions. Compost ingredients are commonly referred to as materials, amendments, bulking agents or feedstocks. A good recipe or mix of amendments will target a carbon-to-nitrogen ratio within a range of 15:1 to 35:1, moisture percentages within a range of 40 to 60%, and a particle size range between 0.1 to 2 inches. Keeping the mixture within these ranges will result in robust compost activity.

Heat production with temperatures ranging from 130 to 150 degrees Fahrenheit indicates an active compost process. Be sure to monitor the temperature within the composting mass. A decrease in temperature indicates that activity has decreased. Aerating, adding moisture or doing both will reactivate the composting process and the temperature will rise again. Properly timed aeration and moisture management will allow active composting to continue in repeated cycles for months.

If the compost recipe characteristics fall outside of the suggested ranges, the growth and reproduction of the microorganisms performing the main role in composting may be restricted. Typical problems with on-farm composting of manures and other organic amendments include:
•Too much nitrogen (unbalanced carbon-to-nitrogen ratio)
•Too dry (less than 40 percent moisture)
•Too wet (greater than 60 percent moisture)
•Too coarse (particle size greater than 2 inches)

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Recognizing the importance of a balanced compost recipe, Michigan State University (MSU) Extension released a computer tool in 2007 called the Spartan Compost Recipe Optimizer. It assists composters in assembling mixtures of organic materials that actively compost. In 2014, MSU Extension released an improved version, Version 1.04.

The Spartan Compost Recipe Optimizer is a Microsoft Office Excel application that simplifies the planning of compost recipes. This computer application uses Excel's Solver Add-In to automate the process of developing or formulating a compost recipe. Users can determine the amounts of materials they will use in compost mixes based on meeting the compost performance constraints or variables described above (such as percent moisture, carbon-nitrogen ratio and particle size) while minimizing cost. Material constraints and costs are set to limit the amount of individual amendments incorporated in the compost mix. The user sets performance constraints, or targets, for percent moisture, carbon-nitrogen ratio and particle size or bulk density. The user can manage both the material and performance constraints or set them to default values. Spartan Compost Recipe Optimizer incorporates a large library of commonly available amendments to choose from when developing a compost mix. Users may also easily add materials to the library or change the composition of existing library materials to fit their situations.

The 2014 version of Spartan Compost Recipe Optimizer contains an even larger library of materials than the previous version for users to select from when developing a recipe. In 2013, MSU Extension educators identified and collected samples of useful composting amendments available on Michigan dairy farms. Each material was analyzed tfor their compost qualities. Results were added into the library of ingredients. These materials represented waste feeds, manures and other products that producers might have readily available on their farms.

The material analyzed includes:
•Corn stover
•Pen pack manure
•Calf hutch-pack bedding/manure
•Aisle-scraped cow manure
•Maternity pen bedding
•Sawdust or wood waste
•Spoiled or rotten feed
•Refused feed or orts
•Raw sugar-beet chips

Spartan Compost Recipe Optimizer is the only tool available that automatically finds the least cost compost recipe that will actively decompose. Other computer spreadsheets available on the Web for making compost recipes require that the user manually set amounts for amendments in a compost mix. This time-consuming and confusing trial-and-error process does not provide the user with the tools or adequate information to reduce amendment costs. Producers can use the Spartan Compost Recipe Optimizer to analyze composting manures, organic and crop residues and animal mortalities. Using this tool program will lead to greater composting success and conservation of more nutrients and greater protection of the environment, and animal and human health.

Download the free Spartan Compost Recipe Optimizer from MSU Extension. Go to https://www.msu.edu/~rozeboom/. Click on "Composting Tools." You'll find the tool at the top of the list.

Dale Rozeboom is an MSU professor of animal science and an MSU Extension specialist. You can reach him at [email protected].

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