Compost Analysis Proficiency Program


The CAP program

CAP is a laboratory quality assurance program which is conducted as tri-annual exchanges of three [3] compost materials, each submitted in blind triplicate (3 × 3 × 3 = 27) for each of two testing tiers. Tier I. Inorganic; and Tier II. Inorganic plus Biological. Refer to Compost Analysis Proficiency Program Test Parameters(link to Test Methods #4). With the completion of each exchange, participating laboratories will be provided a statistical report with data as to their individual performance on each analysis. Statistical results of each exchange (Link to #2) and list of participating laboratories (link to #3) are accessible as Acrobat Reader pdf files.

Work Plan

The project will include the collection of up to nine [9] reference compost materials from across the United States, corresponding to the diversity of feed stocks and composting technologies employed by Participating STA Certified Compost Facilities.

Tier I
Each Tier I reference sample material is air dried, pulverized to pass a 1.0-mm screed and blended in a Patterson-Kelley V shell blender. Samples are packaged in 600 gram HDPE bottles. Three [3] air dry samples are submitted in blind triplicate [3] to the participating laboratories using regular mail.

Tier II (Required for STA Certified Compost labs)
Each Tier II reference sample represents a biologically active, moist compost. Individual samples are packaged in 600 gram HDPE bottles. quantities at wet ice temperature using chemical ice packs. Three [3] as-received moist samples are submitted in blind triplicate [3] to the participating laboratories using overnight express delivery. The STA Certified Compost Chain of Custody Form is used to track sample condition, timeliness of delivery and laboratory sample preparation. All USCC Seal of Testing Assurance Laboratories (STA) are required to enroll in the Tier II CAP Program. Each lab receives advance notice of sample delivery; notification is made by E-mail and fax one week prior to sample shipment. Confirmation of scheduling with CAP Project Leader is required.

Lab Proficiency Evaluation
Selected test methods from TMECC will be utilized in the CAP program. Results for each of the three compost sample exchanges will be statistically analyzed using median and MAD (median absolute deviation statistics), and measures of intra-laboratory repeatability and inter-laboratory reproducibility will be calculated. Laboratories providing data exceeding a 90% confidence interval of the median of each analysis parameter will be flagged as an outlier. Within 30 days of completion of an exchange, labs will be receive a report on proficiency. Project budget is based upon the enrolment of laboratories in the Tier I program, and laboratories enrolled in the Tier II program. The CAP program was first implemented in 2001.

CAP Project Management and Evaluation

Dr. Robert O. Miller is CAP project leader. He oversees collection of sample materials, compiles analytical data, performs statistical analysis, and prepares CAP reports. Summaries of CAP test results are monitored by the US Composting Council Lab Practices Subcommittee of the USCC Standards and Practices Committee.

Soil and Crop Sciences Department
Colorado State University
Fort Collins, CO 80523
Phone: 970-686-5702
Fax: 970-491-0564

With increasing utilization of compost, testing compost for quality is on the increase.

The publication of the Test Methods Manual for the Examination of Composting and Compost (TMECC), benchmark compost methods now exist for the testing lab industry. To ensure accurate and precise analysis and meet ISO 9001 requirements, a laboratory proficiency program is needed to provide testing labs with an external means of quality control evaluate laboratory performance, and evaluate inter-lab method performance.

CAP Exchange Report

CAP Summaries and Program Reports are provided in pdf v.4 format. Please download and use the most current version of Acrobat Reader. Go to the Adobe site to download free Acrobat Reader.

Known Browser Problems: If your browser cannot open pdf files, right-click the hyperlink text of interest and save the target file to your hard drive. Then open the downloaded pdf file using Acrobat Reader.

CAP Participating Laboratories

    • The underlined laboratory names are links to that labs web site.
    • How to sign up for Tier I or Tier II sample exchanges. [form]
    • Where to send payment when enrolling in the CAP program [form]
    • How to sign up for Tier I or Tier II sample exchanges.
    • Where to send payment when enrolling in a CAP program.


2018 Tier II CAP Participants

A&L Great Lakes Labs
3505 Conestoga Drive
Fort Wayne, IN 46808
Phone: 260-483-4759
Fax: 260-483-5274

A & L Western AG Labs
1311 Woodland Ave #1
Modesto, CA 95351
Phone: 209-529-4080

Ag Analytical Services Lab
Penn State University
Tower Road University Park, PA 16802
Phone: 814-863-0841
Fax: 814-863-4540

AgroLab Inc.
101 Clukey Drive
Harrington, DE 19952
Phone: 302-566-6094
Fax: 302-258-0766

E3 Laboratories Inc.
360 York Road, Unit 10
Niagara on the Lake, ON, L0S1JO, Canada
Phone: 905-641-9000 ext.555

Environmental Research and Innovation Center
University of Wisconsin-Oshkosh800 Algoma Blvd.
Oshkosh, WI 54901
Phone: 920-424-3148

Midwest Laboratories Inc.
13611 B St.
Omaha, NE 68144
Phone: 402-334-7770
Fax: 402-334-9121

Soil Control Lab
42 Hangar Way
Watsonville, CA 95076
Phone: 831-724-5422
Fax: 831-724-3188

Soil Test Farm Consultants
2925 Driggs Dr.
Moses Lake, WA 98837
Phone: 509-765-1622

Spectra Laboratories
2221 Ross Way
Tacoma, WA 98421

4915 W Monte Cristo Rd.
Edinburg, Texas 78541
Phone: 956-383-0739


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