California Integrated Waste Management Board

Purchasing Compost & Mulch

Compost Quality Standards

Quality Standards for Finished Compost
Indicator Quality Standard for Finished Compost
Visual  All material is dark brown (black indicates possible burning).
 Parent material is no longer visible.
 Structure is mixture of fine and medium size particle and humus crumbs.
Physical  Moisture: 30-40%, Fine Texture (all below 1/8" mesh)
Odor  Smells like rich humus from the forest floor; no ammonia or anaerobic odor.
Nutrient  Carbon:Nitrogen Ratio  <17:1
 Total Organic Matter  20-35%
 Total Nitrogen  1.0-2.0%
 Nitrate Nitrogen  250-350 PPM
 Nitrite Nitrogen  0 PPM
 Sulfide  0 PPM
 Ammonium  0 or trace
 pH  6.5-8.5
 Cation Exchange Capacity (CEC)  >60 meq/100g
 Humic Acid Content  5-15%
 ERGS Reading  5,000-15,000 mS/cm
Microbiological  Heterotrophic Plate Count  1 x 108 -  1 x 1010 CFU/gdw
 Anaerobic Plate Count  Aerobes: Anaerobes at 10:1 or greater
 Yeasts and Molds  1 x 103 - 1 x 105 CFU/gdw
 Actinomycetes  1 x 106 - 1 x 108 CFU/gdw
 Pseudomonads  1 x 103 - 1 x 106 CFU/gdw
 Nitrogen-Fixing Bacteria  1 x 103 - 1 x 106 CFU/gdw
 Compost Maturity  >50% on Maturity Index at dilution rate appropriate for compost application.
 Compost Stability  <100 mg O2/Kg compost dry solids-hour
 E. coli  < 3 E. coli/g
 Fecal Coliforms  <1000 MPN/g of dry solids
 Salmonella  < 3 MPN/4g total solids
Prepared by:
Organic Ag Advisors
P.O. Box 942
North San Juan, CA  95960 
(530) 292-3619

BBC Laboratories, Inc.
1217 North Stadem Drive
Tempe, AZ  85281
(480) 967-5931
www.bbclabs.com
Last updated: March 18, 2004
Organic Materials Management http://www.ciwmb.ca.gov/Organics/
Contacts: http://www.ciwmb.ca.gov/Organics/Contacts.htm