Product Quality
CalRecycle regulations (Title 14, CCR, Division 7, Subchapter 3.1) require that compost produced by commercial scale composting operations and facilities protect public health and safety. This includes testing product quality, including metal concentrations, physical contamination levels, and pathogen levels. Compost purchasers require additional information from suppliers in order to ensure the product meets specific needs, such as for erosion control or specific crops. The quality of compost and mulch products can be determined by testing for specific characteristics, including pH, soluble salts, nutrient content, organic matter, maturity, stability, and physical contaminants (i.e., inerts, including glass, metal, and plastic). Appropriate ranges for specific characteristics depend on the type of application.
Specifications
Compost and mulch specifications identify the value ranges for parameters that ensure products meeting these values are suitable for a given use. Caltrans incorporates CalRecycle’s product quality standards for metals and pathogens, but its physical contaminant requirements may differ slightly. Caltrans specifications require that compost meet the values shown in the following tables:
| Quality characteristic | Test methoda | Requirement | |||
|---|---|---|---|---|---|
| Fine | Medium/Coarse | ||||
| pH | TMECC 04.11-A | 6-8.5 | 6-8.5 | ||
| Soluble salts (dS/m) | TMECC 04.10-A | 0-10 | 0-10 | ||
| Moisture Content (% dry weight) | TMECC 03.09-A | 25-60 | 25-60 | ||
Organic matter content (% dry weight) | TMECC 05.07-A | 30-70 | 30-100 | ||
| Maturity (seed emergence) (% relative to positive control) | TMECC 05.05-A | 80 or above | 80 or above | ||
| Maturity (seedling vigor) (% relative to positive control) | TMECC 05.05-A | 80 or above | 80 or above |
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| Stability (mg CO2-C/g OM per day) | TMECC 05.08-B | 5 or below | 8 or below |
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| Pathogen Salmonella (most probable number per 4 grams dry weight basis) | TMECC 07.01-B | < 3 | < 3 | ||
| Pathogen Fecal coliform (most probable number per gram dry weight basis) | TMECC 07.01-B | < 1,000 | < 1,000 | ||
| Physical contaminants (% dry weight) Plastic, glass, and metal | TMECC 02.02-C | Combined Total: < 0.5 | Combined Total: < 1.0 |
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| Film plastic (% dry weight) | TMECC 02.02-C | Combined Total: < 0.1% | Combined Total: < 0.1% |
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a TMECC refers to Test Methods for the Examination of Composting and Compost, published by the United States Department of Agriculture and the United States Compost Council (USCC).
The particle size must comply with the requirements shown in the following table:
| Quality characteristic | Test methoda | Requirement | |||
|---|---|---|---|---|---|
| Min | Max | ||||
| Gradation Fine:(dry weight % passing) 1-inch sieve 3/8-inch sieve | TMECC 02.02-B | 100 95 | -- -- |
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| Gradation Medium:(dry weight % passing) 2-inch sieve 3/8-inch sieve | TMECC 02.02-B | 95 40 | -- 55 |
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| Gradation Coarse:(dry weight % passing) 3-inch sieve 3/8-inch sieve | TMECC 02.02-B | 95 25 | -- 35 |
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a TMECC refers to Test Methods for the Examination of Composting and Compost, published by the United States Department of Agriculture and the United States Compost Council (USCC).
How to Verify that Compost and Mulch Products Meet Specifications
In order to verify that compost and mulch products meet a given specification, test for the parameters identified in the specification in accordance with standardized methodologies, such as the Test Methods for the Examination of Compost and Composting (TMECC) used for purposes of the United States Composting Council’s Seal of Testing Assurance (STA) program. The STA program requires compost be tested by an approved laboratory capable of performing all the specified methods and meeting other program requirements. A laboratory approved through the STA program tests submitted compost samples in accordance with the TMECC. The laboratory sends a Technical Data Sheet containing the results to the person that submitted the sample. Note that the Technical Data Sheet verifies that the compost sample submitted for testing meets the above Caltrans specification for a fine gradation of compost as all parameters are within the ranges identified in its specifications.
Resources
Compost and Mulch Specifications
- Caltrans Standard Specifications. The California Department of Transportation (Caltrans) website has Standard Specifications and related information.
- Caltrans Erosion Control Toolbox. The Caltrans website has resources for project managers including specifications, publications, compost calculators, and event schedules.
- “Improving Roadside Revegetation and Stormwater Quality with Compost-Based BMPs.” The Caltrans Landscape Architecture Program, in partnership with CalRecycle, University of California Riverside, University of Washington, Filtrexx Sustainable Technologies, Salix Applied Earthcare, United States Composting Council, California Compost Coalition, and R. Alexander Associates, Inc., provided training on compost-based Best Management Practices to improve roadside revegetation, control erosion, filter stormwater, reduce runoff, and improve stormwater quality.
How to Find the Right Product
- Compost: Matching Performance Needs with Product Characteristics. CalRecycle created a publication to assist you in finding the right product for your specific needs.
For more information contact: Organic Materials, organics@calrecycle.ca.gov