«SUPPORT DOCUMENT FOR COMPOST QUALITY CRITERIA NATIONAL STANDARD OF CANADA (CAN/BNQ 0413-200) THE CANADIAN COUNCIL OF MINISTERS OF THE ENVIRONMENT ...»
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. This approach was adopted by the BNQ standardization committee for Types AA and A trace element concentrations in compost.
Other issues that were discussed include the following:
• cumulative application limits ultimately affect long-term soil trace element levels more than product quality standards;
• the no-net degradation and best achievable approach for the product quality are not based on risk assessment; and
• both the no-net degradation and best-achievable criteria ultimately lead to the source- separation on MSW.
Table III presents the maximum trace element limits proposed by the CCME for Categories A and B compost.
6.3.3 AAFC Position AAFC's limits for trace elements in compost are those described in Trade Memorandum T-~93.
These limits have existed for over 15 years and no modifications of the existing numbers are currently being contemplated. There is, however, the possibility of additional elements being added to the list.
Table IV presents the maximum acceptable trace element concentrations in specified products from Trade Memorandum T-4-93. These limits were adopted by the standardization committee for Type B compost. Table IV also presents the maximum acceptable cumulative metal additions Support Document for Compost Quality Criteria to soil, as described in Trade Memorandum T-4-93.
Based on the maximum acceptable cumulative limits for metal additions to soil, the maximum acceptable trace element concentrations in compost were calculated by assuming an application rate of 4,400 kg/hm2/yr1of dry-weight compost, which may contain up to 5 percent of nitrogen (by dry weight) and 50 percent humidity, based on a 45 year-period.
As an example, the maximum acceptable cumulative addition for arsenic (As) is 15 kg/ha. If we were to apply 4,400 kg of dry weight compost/ha for 45 years, the maximum As concentration in
compost would be calculated as follows:
When the present standard was being developed, the maximum acceptable concentration limits for chromium (Cr) and copper (Cu) did not exist in the Fertilizers Act. As a result, the calculations for these two trace elements were done according to the equation used for the other trace elements (cumulative addition, application rate and period of application). The maximum acceptable limits for cumulative additions of chromium and copper, 210 and 150 kg/ha respectively, were taken from the OMAF document (1978), which was revised in January 1986.
Based on the calculations presented above, the maximum acceptable cumulative addition limits are 1,060 mg/kg for Cr and 757 mg/kg for Cu.
The standardization committee adopted these two limits, which are presented in Table II for Type B compost.
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6.4 PATHOGENIC ORGANISMS The feedstocks used to make compost sometimes contains pathogenic organisms. As a result, the compost may also contain pathogenic organisms; this is a concern, given the possible ensuing health risks.
From a regulatory standpoint, two approaches exist for evaluating compost and sludge safety, as
• the evaluation of processes to further reduce pathogens (PFRPs); and
The ability to eliminate or diminish the number of pathogenic organisms was evaluated for a number of sludge treatment methods. PFRPs are processes that reduce the number of pathogenic organisms to an acceptable level. These processes specify the treatment standards for products (temperatures, time of exposure). These treatment standards were proposed by the U.S. EPA in 1979 and, since then, have been used by many organizations as a substitute for direct analysis of pathogenic organisms (Appendix A, discussion paper no.5, 1993).
The approach that identifies the type and number of pathogenic organisms in products bears no relation to the type of treatment and does not discriminate against any new processes. To reduce the cost inherent in these types of analyses, indicator organisms are used as substitutes for pathogenic organisms.
Finally, in order to ensure product safety, a combination of these two approaches can be used to detect the presence of pathogenic organisms in compost and in sludge (Appendix A, discussion paper no.5, 1993).
6.4.1 BNQ Standard In the early stages of its work, the Committee took into consideration the combination of the two approaches (PFRPs with the faecal coliform and salmonellae count) and the use of two additional criteria for sludge-based compost (viruses and helminth ova).
The standardization committee faced a problem: PFRPs are linked to processes that must maintain a proper temperature for a specified time. Within the scope of the standardization efforts, these conditions are difficult to verify by analyzing the final product, which creates a problem determining if the compost complies with the standard.
Moreover, the standardization committee wished to give industry the necessary flexibility to develop new composting treatment methods that would allow for a further reduction in the number of pathogenic organisms.
Initially, the Committee adopted two additional criteria for sludge-based compost. But in the end, the requirements regarding pathogenic organisms became identical for all types of compost. This decision was made based in part on the fact that available evaluation methods for viruses and helminth ova are very costly, complex, not very sensitive and not always reliable. Moreover, the sophistication level of these methods of analysis limits the number of laboratories capable of conducting this type of analysis.
Support Document for Compost Quality Criteria 28 Therefore, for the three types of compost described in the BNQ standard, the pathogenic
organism content must not exceed the following limits:
These organisms (faecal coliforms and salmonellae) serve as compost safety indicators with respect to the potential presence of pathogenic organisms in compost.
The limits proposed by the BNQ committee are based on USEPA limits and are in accordance with those proposed in the CCME's compost guidelines and with those included in the AAFC proposals.
6.4.2 CCME Position 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 Section A or B depending on the feedstock source.
A. When a 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 a 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 550C 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.
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Salmonella sp. 3 MPN/4g total solids calculated on a dry weight basis Note: faecal coliforms are good long-term indicators of pathogenic bacteria B When compost contains feedstock know to be high in human pathogens, the following
criteria shall be met:
1. Undergo a treatment (described in Section A, above) or other process recognized as equivalent by the relevant province or territory.
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 6.4.3 AAFC Position For regulatory organizations to allow the sale and use of compost and sludge, these products must be safe, that is, they must not contain any pathogenic organisms or the type and number of such organisms must be reduced to an acceptable level. For the application activities and
compliance with these requirements, the following limits have been retained:
• non-detectable salmonellae ( 3 MPN/4g total solids).
It should be noted that the requirements are the same as those adopted by the BNQ standardization committee and that they come from the U.S. EPA's sludge regulations.
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6.5 ORGANIC CONTAMINANTS There is likely a very high number of organic contaminants to be found in compost made from collected and treated industrial and household waste. Each year, the use of new compounds increases by a few thousand. Some of these compounds break down or undergo a transformation during the composting operations, while others remain stable. The presence of organic contaminants in compost used on soils could represent a potential risk to the environment and to the quality of crops intended for human or animal consumption.
6.5.1 BNQ Standard The Committee decided that, at the present time, there is no valid reason for including organic contaminant criteria in the standard. This stance can be reconsidered and modified should any information or scientific findings justify a review.
In light of the results obtained during a study commissioned by the CCME and the AAFC (Appendix A, discussion paper no.1, 1993) on the current world-wide situation regarding organic contaminants (FlAPs and PCBs), the standardization committee did not adopt criteria for these compounds or for the following compounds: dioxins, furans, chlorinated benzenes, pesticides, organochlorines, ester phthalates, haloethers, nitrosamines, phenols, cresols, etc. The
Committee's decision was based on the following considerations:
• Very little information exists on organic contaminants in Canadian compost. For Canadian sludge, data are limited and unreliable. Reliable data must be obtained to evaluate the risks associated with the application of these organic contaminants on soils (Appendix A, discussion paper no.1, 1993).
• Even if the current data do not allow for an evaluation of risk, it would seem that the concentrations of organic contaminants in sludge and compost of Canadian origin, and from elsewhere, are low and do not pose a significant risk to the food chain or the environment (Appendix A, discussion paper no.1, 1993). For one thing, the assimilation of PCBs in soil, through plants, is limited. Also, the compost analysis program conducted by AAFC, in 1993 and 1994, did not discover any traces of PCBs in the approximately 50 different composts that were evaluated.
The study on leaf and yard waste composting conducted in 1993 (Association of Municipal
Recycling Co-ordinators 1993) presents the following information:
The data compiled on compost made with green waste show trace or non-detectable concentrations of the main organochiorinated pesticides. The concentrations of these compounds are generally found at the detection limit of the instruments used in this type of analysis.
Many commonly available and commonly used insecticides and herbicides are nonpersistent; i.e., they quickly break down or disperse following their application. As a result, the residue concentrations in compost made from green waste (Canadian or American) are not of major concern.
6.5.2 CCME Position The CCME decided that, at the present time, there is no valid reason to support the inclusion of organic contaminant limits in its document. This stance will be reconsidered and modified should any information or scientific findings justify a review.
The provinces and territories may wish to establish specific requirements for organic contaminants based on to feedstock source.
6.5.3 AAFC Position The AAFC decided that, at the present time, there is no valid reason to support the adoption of criteria for organic contaminants in compost.
The compost and sludge sold in Canada are regulated by the AAFC in accordance with the Fertilizers Act and Regulation. For compost, organic contaminants can be evaluated on a caseby-case basis depending on the feedstock used.
NOTE: The CCME, the BNQ and AAFC all require further information on organic contaminants in Canadian compost. Therefore, a review, compilation and evaluation of research in this field is required. Special attention should be paid to dioxins, furans and pesticides.
During the development of the standard, the inclusion of limits on organic contaminants in compost could not be supported or justified by reference to the scientific data. However, this stance may have to be modified when scientific advancement in the field and new scientific data justify a review.
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7.0 OTHER CHARACTERISTICS
In the area of safety and health concerns regarding the use of compost, the standard takes into consideration the following four categories of criteria: foreign matter, maturity, pathogenic organisms and trace elements. However, compost, which is primarily an organic soil conditioner, also has other characteristics by which its agronomic value can be evaluated.
7.1 BNQ STANDARD
7.1.1 Organic Matter Organic matter content in compost is an important characteristic for evaluating product quality.