CCME COMPOST CRITERIA
The term compost is defined as “A solid mature product resulting from composting,” where composting is defined as “a managed process of bio-oxidation of a solid heterogeneous organic substrate including a thermophilic phase."
Four categories of quality criteria assess if you are successful in producing a Class ‘A’ compost. The four categories are:
- 1.0 Maturity,
- 2.0 Foreign matter,
- 3.0 Trace elements, and
- 4.0 Pathogenic organisms.
1.0 Maturity
“The maturity of compost is an important characteristic to consider when evaluating the quality of the product, given the harmful effects of immature compost use on plant growth. Maturity is an inherent compost characteristic: if the product of the composting process is not mature, the term "compost" cannot be used” .
The CCME position on compost maturity suggests that compost is considered mature if it meets “two of the following three criteria:
- a C/N ratio , 25,
- an oxygen uptake < 150 mg O2/kg volatile solids per hour, and
- germination of cress (Lepidium sativum) seeds and of radish (Raphanus sativus) seeds in compost must be greater than 90 percent of the germination rate of the control sample, and the growth rate of plants grown in a mixture of compost and soil must not differ more than 50 percent in comparison with the control sample
OR
- compost will not reheat upon standing to greater than 200C above ambient temperature, and
- compost must be allowed to mature for at least 21 days after the thermophilic phase is completed.
OR
- Reduction of organic matter must be 60 percent by weight, and
- compost must be allowed to mature for at least 21 days after the thermophilic phase is completed.
OR
- If no other determination of maturity is made, the compost must be cured for a six-month period. The state of the curing pile must be conducive to aerobic biological activity. The curing stage begins when the pathogen reduction process is complete and the compost no longer reheats to thermophilic temperatures."
“Immature composts continue to break down once they are incorporated into the soil. This can affect plant health by consuming or tying up two resources that growing roots need. The high level of microbial activity in unfinished compost requires a large intake of oxygen, and the microbes may pull this from the surrounding soil, essentially suffocating the roots.”
Based on the above requirements compost maturity can be evaluated based on oxygen uptake rate. Oxygen uptake rate is a measurement of “the amount of oxygen consumed by the metabolic activity of aerobic micro-organisms in a compost sample over a period of time, which permits an estimate of the biological activity of the compost. As the biological activity of compost diminishes as the composting process nears completion, oxygen uptake decreases and may be used to provide an indication of compost maturity.” “Compost shall be mature at the time of sale and distribution”
2.0 Foreign Matter
The CCME guideline states, “mineral soils, sand, rocks and wood are not considered to be foreign matter. Both Category A and Category B compost must be virtually free of foreign matter that may cause nuisance, damage or injury to humans, plants or animals, during or resulting from intended use. The compost must not contain any sharp foreign matter measuring over 3 mm in any dimension or any foreign matter greater than 25 mm in any dimension” .
3.0 Pathogenic Organisms
“As pathogenic organisms may be present in the compost feedstock, the compost itself may also contain pathogenic organisms and, as a result, may pose health risks. To adequately reduce these health risks, the compost shall conform to the criteria outlined in either Clause A or B below depending on the feedstock source.
Clause A: When compost does not contain feedstock known to be high in human pathogens, the following criteria shall be met:
1. The compost shall undergo the following treatment or other process recognized an equivalent by the relevant authority.
Using the in-vessel composting method, the solid waste shall be maintained at operating conditions of 550C or greater for three days.
Using the windrow composting method, the solid waste shall attain a temperature of 55ºC or greater for at least 15 days during the composting period. Also, during the high temperature period, the windrow shall be turned at least five times.
Using the aerated static pile composting method, the solid waste will be maintained at operating conditions of 550C or greater for three days. The preferable practice is to cover the pile with an insulating layer of material, such as cured compost or wood chips, to ensure that all areas of the feed material are exposed to the required temperature.
OR
2. Organisms shall not exceed the following:
faecal coliforms < 1000 most probable number (MPN)/g of total solids calculated on a dry weight basis, and
Salmonella sp. <3 MPN/4g total solids calculated on a dry weight basis
Clause B: When compost contains feedstock know to be high in human pathogens, the following criteria shall be met:
1. Undergo a treatment (described in Clause A, above) or other process recognized as equivalent by the relevant province or territory.
AND
2. Organisms shall not exceed the following:
faecal coliforms < 1000 MPN/g of total solids calculated on a dry weight basis, or
Salmonella sp. <3 MPN/4g total solids calculated on a dry weight basis.”
4.0 Trace Elements
“For the CCME, Category A trace element concentrations come from the maximum background concentrations derived from the arithmetic mean plus 3 standard deviations of rural and agricultural soils from Alberta, Ontario and Quebec, and from limits established through the British Columbia best achievable approach.”
CCME Maximum Trace Element Concentration Limits for Category A Compost
Parameter |
Unit S |
Compost Quality Criteria Category A |
| Arsenic |
ppm |
< |
13 |
| Cadmium |
ppm |
< |
3 |
| Chromium |
ppm |
< |
210 |
| Cobalt |
ppm |
< |
34 |
| Copper |
ppm |
< |
100 |
| Lead |
ppm |
< |
150 |
| Mercury |
ppm |
< |
0.8 |
| Molybdenum |
ppm |
< |
5 |
| Nickel |
ppm |
< |
62 |
| Selenium |
ppm |
< |
2 |
| Zinc |
ppm |
< |
500 |
|
