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«SUPPORT DOCUMENT FOR COMPOST QUALITY CRITERIA NATIONAL STANDARD OF CANADA (CAN/BNQ 0413-200) THE CANADIAN COUNCIL OF MINISTERS OF THE ENVIRONMENT ...»

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In other words, the compost must not contain any sharp foreign matter measuring more than 3 mm.

6.2.1.1 Evaluation of Samples Containing Foreign Matter Compost samples containing various quantities of foreign matter were prepared by the Centre de recherche industrielle du Québec (CRIQ), thanks to the financial support provided by the Consortium québécois sur le compostage and AAFC. The objective of this procedure was to determine the relationship between the mass quantity of foreign matter and the visual aspect of compost.

In total, 49 compost samples (two independent series) with variable foreign matter content were examined by the Committee during two meetings, one held in February and the other in May

1994. The foreign matter, introduced according to compost dry-weight mass, included particles of heavy and light plastic, of glass and of metal measuring 2 to 25 mm in any dimension. All the samples were put into transparent plastic bags, numbered and placed on a table; the evaluators were not aware of the foreign matter content in the samples. The members present during the two evaluations then examined each sample and classified each one according to its apparent foreign matter content: Category A, Category B or as a product that should not be sold (rejected).

The members of the Committee were surprised to see the relatively uniform results achieved in the evaluations.

The visual evaluation of the samples brought out the following points:

There were no patterns to the results except for the foreign matter weight distribution as a percentage of the sample.

The Committee realized that the plastic content in compost could be better evaluated using dimensional limits and observation instead of weight. The Committee wanted to take into consideration the aesthetic, safety and market development aspects of compost but, after the first series of evaluations, it experienced some difficulties in determining dimensional and weight limits for foreign matter.

• The subjects of glass crushing, acceptable quantities and dimensions for plastic particles, as well as source separation, were all addressed. The foreign matter dimensional limit proved critical to the evaluation of foreign matter.

Support Document for Compost Quality Criteria While knowing that the safety and aesthetic aspects could be evaluated by a visual examination, the necessity of determining a weight limit (percentage of foreign matter by dry weight) was discussed.

It is necessary to have a sampling protocol and a standardized test for the visual and physical examinations of samples. The effect of rain, the definition of the word "sharp" and the representativeness of the samples were also discussed.

6.2.1.2 An Additional Method For Evaluating Foreign Matter

The Committee recognized the complexity of using a method based on foreign matter mass proportion and, therefore, also studied the possibility of using a simple visual method. The latter would rely on a visual examination and the collection of foreign matter from compost sifted with the help of a series of standardized sifters. With this approach, there is more tolerance of foreign matter in compost.

A specific quantity of compost would be spread out on a smooth and squared surface in order to facilitate the counting of foreign matter. The evaluator would visually identify the presence of foreign matter and would determine, by means of a dozen compost samples, the dimensions of

the foreign matter. This method was not adopted for the following reasons:

the method should be developed and tested to determine its validity;

standardized equivalent method does not exist; and

• the Committee did not reach a consensus on the adoption of such a method.

6.2.2 CCME Position In the guidelines prepared by the CCME, 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.

The CCME position is based on concepts similar to those of the BNQ committee regarding tolerance limits for foreign matter.

6.2.3 AAFC Position Compost must be free of harmful foreign matter that may cause harm or injury to humans, plants or animals, during or resulting from intended use. The compost must not contain any sharp Support Document for Compost Quality Criteria foreign matter measuring over 3 mm in any dimension. The AAFC position regarding foreign matter takes into consideration the product safety aspect by considering the level of tolerance for sharp objects; the aesthetic aspect of compost is not taken into consideration.

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6.3.1 BNO Standard

Within the context of the work being done on standardization, a "trace element" is defined as:

"A chemical element present in compost at a very low concentration."

The trace elements considered by the Committee include those that are essential to plant growth (particularly Cu, Mo, Zn) and heavy metals which, depending on their concentration in the soil, could be harmful to human health and to the environment. Environmental and agronomical concerns regarding the presence of trace elements in compost vary according to the aspect under consideration. Evaluating the level of risk and the possible consequences to human and environmental health for each of the trace elements considered is complex and requires a great deal of expertise. Given these constraints, the BNQ standardization committee considered concepts whose respective principles led to maximum trace element limits in compost that vary depending on the concept being considered.





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Before establishing the maximum acceptable trace elements limits for each of the three compost

classes, the following three approaches were taken into consideration:

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1) No net degradation The no net degradation approach is based on the principle that product use (e.g., compost) does not affect the normal background level of toxic compounds in the environment. According to this approach, "toxic", "normal" and "background" are fixed terms that can be precisely defined.

Support Document for Compost Quality Criteria The background is defined in an Environment Canada document (1991) as being "the concentration of chemical substances found in an environment removed from any source of industrial activity for a specific area and for a region considered to be relatively uninfluenced by industrial activity."

The no net degradation concept generally recognizes that the maximum acceptable trace element concentrations in compost should be calculated by taking the arithmetic average of the background levels and adding the equivalent of three standard deviations.

Of the three approaches taken into consideration, this one calculates the strictest critical limits. In Canada, the approach used to determine the critical limits for trace elements in compost is generally based on the concept of no net degradation or on a combination of the best achievable approach and the no net degradation approach.

2) No observable adverse effects level The no observable adverse effects level (NOAEL) approach, also called the risk

approach, is based on the following assumptions:

• there is sufficient information on trace element dynamics in the ecosystem to predict, with certainty, the acceptable levels of contaminants; and

• there are sufficient observations on the absence of adverse effects linked to applications of metals contained in the sludge of purification plants.

This information is used to establish critical limits for contaminants at levels that ensure the absence of adverse effects on the health of both humans and the environment.

Three major reasons justify why the Committee chose not to adopt this approach: the risk analysis is complex and costly, the methodology used to analyse risk is debatable and the limits obtained using this approach would be much more permissive than those obtained using the no net degradation approach.

3) Best achievable approach The best achievable approach concept rests on the assumption that the best available technology for obtaining the desired final product should be used to define the maximum acceptable trace element concentrations in compost (Bureau de normalisation du Québec 1995). In line with this concept, British Columbia regulations (British Columbia, Waste Management Act 1993) regarding trace element concentrations in compost were established to encourage source separation management programs.

Support Document for Compost Quality Criteria Analytical data from Alberta, Ontario and Quebec on trace element background concentrations in agricultural soils were made available to the CCME committee. Thus, these are the data that were used in considering metal standards. Table I presents trace element background concentrations in Canadian soils for the provinces of Quebec, Ontario and Alberta. Using an identical approach, the background concentrations for these three provinces were obtained by calculating the average trace element concentration in the soil and adding three standard deviations (X + 3 õ).

The Quebec data come from the analysis of the total amount of trace elements in Ap horizon topsoils taken from the 76 major soil series found in the 12 agricultural regions of Quebec. The analyses were conducted on samples ground to 100-mesh fineness and extracted with aqua regia (HCI + HNO3) (Giroux et al. 1992).

The Ontario data come from the analysis of trace elements in rural soils taken at a depth of 0 to 5 cm. The analysis was conducted by the Laboratory Services Branch of the Ontario Ministry of the Environment in accordance with the standard techniques cited in Ontario, Ministry of the Environment, 1989.

For Alberta, the trace element data were obtained by analyzing agricultural soils taken at a depth of 0 to 15 cm (Alberta Environmental Protection 1994).

Table I also presents the trace element concentrations of the British Columbia Class I compost regulations, which were obtained using the best achievable approach (British Columbia, Waste Management Act 1993). The maximum acceptable limits suggested for use of sludge on agricultural land, which were calculated using the NOAEL approach and can be found in the (EPA) Regulation 503, are also presented in Table I (United States, Environmental Protection Agency 1992). Finally, the maximum acceptable concentration limits for products, according to AAFC's Trade Memorandum T-4-93, are also included in Table I.

Initially, the standardization committee decided to adopt the no net degradation approach for establishing the maximum trace element limits for Types AA, A and B. The Committee initially set the trace element concentration limits for Types AA and A based on the highest background concentrations for each of the trace elements found in soils in Alberta, Ontario and Quebec.

However, due to various considerations, the combined approach suggested by the CCME - no net degradation and best achievable approach - was adopted for Types AA and A by the Committee.

Support Document for Compost Quality Criteria The adoption of this approach for trace element limits of compost of Types AA and A compost

was based on the following considerations:

• the background concentrations for in-soil trace elements were provided by only three provinces;

• the comments made during the public consultation process;

• the adoption of the highest limits of the three provinces for which background concentrations were available may cause difficulties in staying true to the no net degradation concept because of the variations in background concentrations among provinces;

• the soil concentration that would result from compost with metals meeting British Columbia's best achievable approach may not actually conflict with the no net degradation;

• the adoption of maximum trace element limits for the micronutrients (Zn, Cu and Mo), from the no net degradation approach, generated low concentration limits in compost; and

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Retained limits for Types AA and A compost of the BNQ standard 1 Giroux et al. 1992 2 Ontario, Ministry of the Environment 1989.

3 Alberta Environmental Protection 1994.

4 British Columbia, Waste Management Act 1993.

5 Folliet 1993.

6 Agriculture Canada 1991.

Support Document for Compost Quality Criteria For BNQ standard Type B compost, the maximum acceptable concentration limits of trace elements come from AAFC Fertilizers Act (Trade Memorandum T-4-93). These limits have been in force for over 15 years: they were developed by a committee of experts that referred to the first version of the guide on the use of sludge on agricultural land prepared by the Ontario Ministry of Agriculture and Food (OMAF 1978). The OMAF document deals particularly with maximum acceptable soil additions for 11 trace elements (kg/ha). After analyzing the available information, AAFC committee revised the OMAF concentrations in 1980 and adopted those included in the Trade Memorandum T-4-93.

Table II presents the trace element concentrations adopted by the BNQ's standardization committee.

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6.3.1.2 Elements Not Considered During the public consultation process, certain individuals expressed a need for limits on the maximum acceptable concentrations of some trace elements in compost, particularly iron (Fe), aluminium (Al) and boron (B). Based on the list established in the CCME and AAFC discussion paper, the standardization committee limited the number of trace elements addressed. The Committee decided to postpone the establishment of limits for these three elements (Fe, Al and B). Differences in speciation and bioavailability of the elements were also not addressed due to the fact that there is no precedent for these kinds of limits and because to investigate the possibility would have been expensive and very time consuming.

6.3.2 CCME Position



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