Reader’s Q & A
BioCycle May 2004, Vol. 45, No. 5, p 14

Q: More and more attention is being given to compost classification criteria by producers and users as well as soil scientists and landscape designers. What key factors are involved in such systems?

A: A good example of what goes into a Compost Classification System (CCS) is provided in the Rocky Mountain Region. Last month, Bob Yost of A1 Organics in Eaton, Colorado and his colleagues prepared a final 2004 version of the region’s CCS which reflected valuable input from industry professionals. “We feel the system in our Rocky Mountain Region offers an effective tool for standardizing the manufacture and use of compost,” writes Yost. Following are excerpts from his report:
The CCS utilizes three basic areas of evaluation to determine the correct class for a given compost product: Analytical – Identifying stability/maturity indicators plus laboratory data; Manufacturing – Certifying that producers follow applicable state, local and federal guidelines to generate the equivalent of Class A compost product; Application/ Risk Assessment – Listing generally appropriate application uses and incorporation information for each class of material, with a corresponding assessment of risk to plant germination and health.
The Rocky Mountain Region CCS assigns specific parameters and acceptable ranges for each class of material. Yost emphasizes that it “endeavors to improve customer confidence in compost, and the additional use of valuable compost products.” The system is divided into these four classes:
Class I – Fully composted, stabilized and mature product that is generally made from nonmanure feedstocks; Will germinate and sustain plants without much risk due to over-application or poor incorporation; May be lower in total nutrient values.
Class II – Fully composted, stabilized and mature product that is generally made from manure based feedstocks (dairy, poultry, equestrian, etc.); Proper application quantity and incorporation is important to plant germination and sustainability; Normally has increased level of nutrients and can be used to supplement fertilizer needs.
Class III – Partially composted or dehydrated product; May be “shredded” or screened but is not mature or stable.
Class IV – Represents raw feedstock materials, such as manure.
APPLICATION RECOMMENDATIONS
Class I – Horticultural, nursery container mixes, turf, seed bed preparation, raised garden, vegetable gardens, topsoil blends, erosion control; Watering to leach excess salts not required; Can be applied at high volume; Incorporation can be at shallower depths; Can be used as a high percentage of the soil profile; Incorporation not critical (top four-inches recommended).
Class II – Turf, sod, seedbed preparation, raised garden, vegetable garden, topsoil blends, erosion control; If possible, incorporate at least 60 days prior to planting and water thoroughly before and after planting; Incorporation is important; Should not be used as high percentage of the soil profile (30 percent maximum); Incorporation in top six inches recommended.
Class III – Crop production, turf and topsoil blends with limitations, erosion control, mulch; If possible, incorporate at least 90 days prior to planting; Deep incorporation and thorough mixing very important; Cannot be used as a high percentage of the soil profile (15 percent maximum); Incorporation in top eight-inches or more recommended.
Class IV – Agriculture; Cannot be used as a high percentage of the soil profile; Incorporation in top ten-inches or more recommended.
Bob Yost is vice president of A1 Organics which operates three composting facilities in Colorado: Eaton; Golden (Lost Antlers) and Keenesburg (Rattler Ridge). Yost can be contacted via phone at (800) 776 1644. Our thanks to him and his colleagues in Colorado for compiling this information on Compost Classification Systems in the region. Readers are invited to send BioCycle their experiences in classifying compost. E-mail: biocycle@jgpress.com along with your questions for this department.