«SUPPORT DOCUMENT FOR COMPOST QUALITY CRITERIA NATIONAL STANDARD OF CANADA (CAN/BNQ 0413-200) THE CANADIAN COUNCIL OF MINISTERS OF THE ENVIRONMENT ...»
In 1993, draft documents on the five categories of criteria (trace elements, pathogenic organisms, organic contaminants, maturity and foreign matter) were prepared to sustain and stimulate discussion on these five main aspects of compost safety and quality. These five discussion papers were distributed to the provinces, the territories and the BNQ. The standardization committee used these papers as references during the process of developing the standard. A list of these Support Document for Compost Quality Criteria discussion papers is presented in Appendix A.
The work done by the BNQ, the CCME and AAFC will produce the following three documents:
a normative document for the industry (the standard), CCME guidelines and an AAFC trade memorandum describing the criteria adopted under the Fertilizers Act.
"Composting" and "compost" are two distinct terms. The former refers to the bio-oxidation process and the latter refers to the resulting product: stabilized organic matter.
Within the scope of the standardization efforts for compost quality, and after consulting several references, it was decided that the definition of the term "compost" would include the notion of process so that it could correspond to AAFC terminology. Appendix B presents all the definitions that were taken into consideration at the committee level.
In the BNQ standard (P 0413-200/1995), the word "compost" is defined as follows:
"A solid mature product resulting from composting, which is a managed process of bio-oxidation of a solid heterogeneous organic substrate including a thermophilic phase. French: compost."
The Fertilizers Act defines "compost" as follows: "A homogeneous and friable mixture of partially decomposed organic matter, with or without soil," and as a synonym for humus and leaf mould. AAFC is aware that this definition no longer reflects the current composting activities in Support Document for Compost Quality Criteria Canada and is working to modify it. AAFC has suggested that since the definition of "compost" used in the BNQ standard corresponds to the concept promoted by AQIC, the provinces and other countries, it should be adopted by AAFC in accordance with the Fertilizers Act. The
following is the definition of "compost" that AAFC anticipates adopting:
"A solid mature product resulting from composting, which is a managed process ofbio-oxidation of a solid heterogeneous organic substrate including a thermophilic phase."
The implementation of a single class of compost, as well as the development of a multi-class approach, was considered and discussed at length by the standardization committee. The Committee reached a consensus to establish a standard comprising of more than one class.
A classification approach based on compost use (non restricted use and restricted use subject to a permit issued, or regulations determined, by regulatory authorities) was also considered by the members of the BNQ standardization committee.
For the five main criteria categories and for each type of compost, the Committee took the
following into consideration when establishing the different acceptable limits:
existing Canadian regulations, policies, laws and guidelines;
existing scientific literature and technical information;
the agronomic value of compost;
analyses of compost made in Canada;
the needs, constraints and interests of compost producers;
the compatibility of the approaches used by the various participants (the CCME, the AAFC and the BNQ);
• the requirements of environmental organizations, various experts and the many concerned stake holders, as expressed during the public consultation.
Support Document for Compost Quality Criteria The BNQ standard, which comprises three types of compost, classifies the products in decreasing order of quality: Types AA, A and B. Globally, the recognition of Types AA, A and B compost is based on the level of compost quality and safety, and not on the end use of the product. The classification itself is based on the total organic matter, foreign matter and trace elements in the compost. The other criteria do not differ between the 3 classes of compost.
Compost classified as Types AA and A is of high quality, while the specified requirements for Type B compost are considered to be the minimum necessary to obtain a good compost. Because of its trace element content, Type B compost must be accompanied by appropriate use instructions when sold and distributed (Bureau de normalisation du Québec 1995).
Types AA and A compost have the same concentration limits for trace elements. All three types of compost have the same criteria regarding water content, maturity and pathogenic organisms.
Regarding trace element concentration, the CCME guidelines recognize two compost categories:
A and B. Category A compost can be used for all types of applications: on agricultural lands, in residential gardens, in horticultural operations, in nurseries or others. For trace elements, Category A criteria meet or are more stringent than the current CCME interim soil quality criteria for contaminated sites. Category A criteria for trace elements are achievable using source separated municipal solid waste feedstock Category B compost may be subject to use restrictions. This compost may require authorization (control) when judged necessary by the provinces or the territories. For Category B compost, the provinces could develop sub-categories according to regional needs.
AAFC recognizes the existence of only one class of compost. This class recognizes the importance of product safety, is based on the limits of Type B compost for trace elements and refers to the requirements of the standard on pathogenic organisms, maturity and the presence of sharp objects. This position represents the fact that AAFC, through the Fertilizers Act, establishes the minimum safety criteria for all compost sold as fertilizers or supplements in Canada.
Support Document for Compost Quality Criteria
6.0 MAIN CRITERIA CONSIDERED FOR THE COMPOST STANDARDIZATIONPROJECT
6.1 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. The many CCME, BNQ and AAFC stakeholders have determined that maturity is an inherent compost characteristic: if the product of the composting process is not mature, the term "compost" cannot be used. This is why the term "mature" is included in the definition of compost as it is defined in the normative document.
The existing methods of evaluating compost maturity are numerous; but many of them are still being perfected. The complexity of interpreting results is one of the problems in choosing a method to evaluate compost maturity. Taking into consideration the current level of knowledge on compost maturity evaluation and the absence of a single test that can adequately evaluate this criterion, the standardization committee determined that the use of several indicators is still necessary to determine compost maturity.
6.1.1 BNO Standard Taking into account the draft discussion paper prepared for the CCME and the AAFC (discussion paper no.3, Appendix A), the Committee considered and adopted three tests for the evaluation of compost maturity. In light of the existing technical information, the standardization committee concluded that there is no single test that is sufficiently trustworthy and scientifically valid to evaluate compost maturity adequately. The Committee therefore recognized the necessity of adopting more than one test to evaluate compost maturity.
The three tests to be used as compost maturity indicators are: C/N ratio, oxygen uptake, and germination and growth rates of plants. The interpretation of the combined and quantifiable results obtained with these methods provides sufficient indicators to determine compost stability levels and to evaluate the qualitative risk factors of using the compost on plants.
According to the BNQ standard, a compost will be deemed mature if it meets two of the
• oxygen uptake rate 150 mg 02/kg volatile solids per hour; and Support Document for Compost Quality Criteria 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.
Initially, it was proposed that compost with a C/N ratio 25 should be acceptable providing the compost producer could provide valid written scientific proof to demonstrate the absence of negative effects on the germination seeds and the growth of plants. Since it is difficult for the BNQ to evaluate and interpret this type of information, it was suggested that two of the three criteria be required instead of eliminating the C/N ratio criterion.
6.1.2 CCME Position
The CCME suggests using the following tests or methods of analysis:
The requirements regarding the criteria and their limits are the same as those adopted by the BNQ standardization committee and which are already in existence in certain provinces. Two of
the three following criteria must be met:
• an oxygen uptake 150 mg 02/kg volatile solids per hour; and
• a germination and growth test using cress (Lepidium sativum) seeds and radish (Raphanus sativus) seeds, which demonstrates an absence of phytotoxic effects.
• Compost will not reheat upon standing to greater than 200C above ambient temperature;
• compost must be allowed to mature for at least 21 days after the thermophilic phase is completed.
• 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.
Support Document for Compost Quality Criteria 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.
6.1.3 AAFC Position For AAFC, a compost must be mature (stable) at the time of sale. AAFC believes that the three compost maturity test indicators described in the BNQ standard are acceptable and satisfactory.
6.2 FOREIGN MATTER When developing an industry standard for compost quality, the presence of foreign matter in compost should be taken into consideration since it has a negative impact on consumers and on the composting industry in general. The consumers look for compost free of visible foreign matter or otherwise harmful foreign matter. In Canada, such compost has been manufactured for many years.
6.2.1 BNO Standard The standardization committee established three different foreign matter mass content limits for Types AA, A and B compost.
After discussion, the standardization committee agreed that soil, sand, rocks and pebbles found in compost are not considered foreign matter. Foreign matter is defined in the BNQ standard as
"Any matter over a 2 mm dimension that results from human intervention and having organic or inorganic constituents such as metal, glass and synthetic polymers (e. g., plastic and rubber) that may be present in the compost but excluding mineral soils, woody material and rocks."
To establish the minimum foreign matter size at 2 mm, the Committee took into consideration that, in geoscience, arable mineral soils are defined according to the distribution of mineral particles smaller than 2 mm for sand (2.0 to 0.05 mm), from 0.05 to 0.002 mm for silt and less than 0.002 mm for clay.
Support Document for Compost Quality Criteria Moreover, for the practical identification of foreign matter, the Committee decided that
particles measuring 2 mm would not be considered foreign matter for the following reasons:
• the possible long-term effects of applying foreign matter of 2 mm on soil were discussed but remain unknown and unexpected.
For the three types of compost, foreign matter of 2 mm in compost must meet the requirements
Type AA compost must not, for all intents and purposes, contain any visible foreign matter (
0.01 percent of the dry weight of the compost). This type of compost has already been commercialized (mostly in bags) by many compost producers in Canada.
To determine the maximum allowable mass percentages for Type A and Type B compost, the Committee evaluated two series of compost samples with varying types and quantities of foreign matter that were unknown to committee members. The evaluation procedure used by the Committee is described in Section 126.96.36.199.
All three types of compost (AA, A, B) must not contain sharp foreign matter, defined in the
standard as follows:
"Any foreign matter measuring over a 3 mm dimension that may cause damage or injury to humans and animals during or resulting from its intended use."
Although the following items do not constitute an exhaustive list, they are the most common
forms of sharp foreign matter:
• objects made mostly of iron or non-ferrous metal objects, such as utensils, electrical cords and appliances, pins, needles, staples, nails and bottle caps; and Support Document for Compost Quality Criteria
• objects made of glass or porcelain, such as containers, dishes, glass panels, light bulbs, fluorescent light tubes, mirrors and broken glass.