Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs

Agricultural Utilization of Fertilizing Residual Materials: Questions and Answers


There’s been some debate in recent year over the benefits and safety of spreading fertilizing residual materials (FRMs) on agricultural land. The Ministry, along with other public and private-sector organizations, has released a number of information documents on the subject. To that same end, the following aims to provide clear answers to the main questions raised by the public, farmers and other stakeholders.

Q: What are FRMs?

A: Fertilizing residual materials (FRMs) are industrial and municipal wastes such as sewage sludge (biosolids), cement kiln dust and wood ash that have beneficial effects on crops or soil. Manure is generally not considered an FRM, because it is an agricultural waste and is governed by special regulations.

Q: How much FRM spreading is there in Québec?

A: Nearly one million tonnes of FRMs are spread on approximately 2.5% of agricultural soils in Québec each year. In fact, land application is one of the main forms of industrial and municipal waste reclamation, making it crucial to the achievement of the goals of the Québec Residual Materials Management Policy 1998-2008. Paper mill sludge accounts for roughly two thirds of all FRMs applied to agricultural land in Québec.

Agricultural spreading of reclaimed FRMs in 1999 (%)

Agricultural spreading of reclaimed FRMs in 1999 (%)

Q: Is land application of FRMs really a form of reclamation or just low-cost waste disposal in disguise?

A: Not all residuals can be converted into fertilizing material. The value of a given residual as a fertilizer or soil amendment must first be demonstrated through agronomic research. Then, analyses must demonstrate that the contaminant concentrations in the residual are within the permissible limits set by the Ministère du Développement durable, de l’Environnement et des Parcs, which are among the most stringent in the world. So fertilizing residuals are, in effect, useful material and not just waste, which is why their reclamation is not only possible, but beneficial.

Q: Does reclamation hinder surplus manure management?

A: Based on statistics, the answer is "no." According to the agro-environmental portrait of Québec farms, only 1% of agricultural soils in the main regions with a manure surplus received FRMs in 1998. And FRMs contributed only around 2% of the total nitrogen and phosphorus application in Québec as a whole, well below the amount added by mineral fertilizers, which are also non-agricultural products. Although FRM-derived loads could increase in the future, they should not account for much more than 5% of the phosphorus and nitrogen added to soil, given the limited amounts of potentially reclaimable residuals. That maximum contribution will be lower for regions with surplus manure, since FRMs tend to be used more in regions with a lack of solid manure. In fact, several kinds of FRMs are of special interest to these regions as a means of offsetting agricultural soil degradation through the addition of organic amendments.

  Distribution of nitrogen and phosphorus loads on agricultural lands in Québec in 1999 (%)

Distribution of nitrogen and phosphorus loads on agricultural lands in Québec in 1999 (%)

Q: Do FRMs contain contaminants?

A: Yes, the same as manure, mineral fertilizers and agricultural lime. Some of the contaminants found in FRMs occur naturally. Cadmium, for example, is a heavy metal that occurs naturally in wood and is therefore found in paper mill sludge. Other contaminants are caused by human activity, such as the presence of copper in municipal sludge, which is mainly the result of corrosion of copper pipes and fittings in household plumbing. However, the Ministère du Développement durable, de l’Environnement et des Parcs has adopted very stringent quality criteria, which has encouraged several industries and municipalities to streamline their processes in order to decrease the contaminant content of residuals ever further for the purposes of agricultural utilization. Interestingly enough, half of the "contaminants" commonly analyzed in FRMs, including copper, chromium, cobalt, iron, zinc, molybdenum, nickel and selenium, are also considered essential trace elements for plants or essential minerals for animals and humans. Their presence in FRMs or manure is therefore not a problem in itself, provided the maximum concentrations are not exceeded.

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Q: Can FRMs harm crops?

A: Agronomic research and the number of farmers applying FRMs to their fields tend to show the beneficial effects fertilizing residuals have on crop productivity and quality. Although there have been a few reported incidents of FRM application resulting in lower yields, subsequent assessment showed that the decreased yields were generally due to agronomic errors rather than to the presence of particular contaminants. Moreover, fertilizer, lime and even manure application can lead to similar problems under certain conditions. Municipal compost made from grass clippings may contain residues of persistent herbicides, such as Clopyralid. These herbicides damage susceptible market crops such as potatoes. Although no incidents of this type have been reported in Québec, an agronomist should be consulted when in doubt. Clopyralid residues in compost are not considered a threat to either human or animal health.

Q: Can spreading residuals contaminate well water?

A: Based on the results of recent risk modelling, the Institut national de santé publique du Québec deems that repeated spreading of FRMs is not liable to cause significant groundwater contamination from such pollutants as cadmium, dioxins and furans. And nitrate contamination of groundwater can be prevented by avoiding overfertilization, by making the participation of agronomists in fertilization plans mandatory, and by respecting the width of buffer zones around wells. Pathogen-related risks are also low when the recommended spreading practices are followed. In fact, there have been no reported cases of water contamination from FRM application in Québec. In spring 2001, the media reported cases of residents of Clarendon, in the Outaouais region, feeling sick, allegedly as a result of private well contamination from the spreading of paper mill sludge. However, after analyzing the well water and assessing the complaints, the regional health and social services board issued a news release saying that no wells had actually been contaminated.

Q: Will FRM application contaminate agricultural soils?

A: Research conducted by Agriculture and Agri-Food Canada, the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec, Université Laval and other research organizations indicate that agricultural utilization of FRMs does not result in soil and crop contamination in the short term. As for the long-term risks, the Institut national de santé publique du Québec considers that normal FRM spreading on the same parcels over a period of 100 years would not cause significant soil contamination from arsenic, cadmium, chromium, copper, mercury, lead or zinc. Theoretically, significant contamination could result if three heavily contaminated fertilizing residuals, each containing maximum contaminant concentrations permitted, were simultaneously applied to the same parcel over a 100-year period. Statistically speaking, however, only around 0.017% of agricultural land, or 345 hectares in Québec as a whole, would receive three heavily contaminated fertilizing residuals in the first year. And the probability of this scenario occurring for 100 consecutive years and of three fertilizing residuals containing the highest level of contaminants is very low.


Q: Is it possible for an unknown contaminant to be present in FRMs and cause irreversible damage to soil over time?

A: Theoretically, yes. However, the probability of that happening is very low. The German experience with municipal biosolids (municipal sludge) is very enlightening in this regard. Germany created a fund to compensate farmers for possible damage caused by land application of municipal biosolids. After eight years of biosolids spreading by 900 participating farmers, no compensation has been paid for either "unknown contaminants" or unforeseeable damage. A number of "safety nets" exist in Québec for minimizing the risk of unknown contaminants. To begin with, FRM characterization studies, particularly of paper mill sludge, were conducted to determine the highest-risk contaminants liable to require regular monitoring. Second, several FRM treatment processes (aerobic digestion, alkalinization, heat drying, composting, etc.) help break down organic contaminants. Receiving soils, which are biologically active, can also purify many organic pollutants. Third, the Centre d’expertise en analyse environnementale du Québec is currently developing toxicity tests (laboratory analyses) to detect the presence of contaminants that are not detectable through standard chemical analyses. These tools will be used for additional protection against unknown contaminants.

Q: Several fertilizing residuals can generate offensive odours. Why not prevent this problem by simply composting all residual materials?

A: The Ministère du Développement durable, de l’Environnement et des Parcs has received numerous complaints about FRM spreading. These complaints concern residuals that are particularly malodorous, such as certain biosolids generated by slaughterhouses and paper mills. The nuisances are generally caused by noncompliance with the prescribed criteria, such as inadequate treatment, too long of a period between application and incorporation into the soil, spreading on holidays or the weekend, etc. Notices of offence were issued, and investigations are under way. Choosing to take a precautionary approach, the Ministère recently required that a lime treatment, frequently used with slaughterhouse sludge, be carried out on site so as to reduce the problem at the source. And paper mills recently implemented additional treatments (including composting and acidification), on a voluntary basis, to substantially decrease odours and biosolids. The Ministère is contemplating making some of these treatments mandatory for strong-smelling FRMs. However, it should be pointed out that composting can also cause odorous emissions, in addition to reducing the nitrogen content of several residuals. Other solutions to odour problems are also being explored, including forest utilization and revegetation of abandoned sandpits located far from inhabited areas.

Q: Can FRM utilization cause health problems in farmers and consumers?

A: According to a recent study by the Institut national de santé publique du Québec, intensive use of FRMs with normal contaminant concentrations does not present a health risk to farmers or the general population where cadmium, dioxins, furans and other such pollutants are concerned. However, highly exposed farmers (intensive and simultaneous use of four FRMs with maximum contaminant concentrations for 100 years, consumption of products produced on the farm, etc.) could theoretically face a slightly higher risk in the long term. In the worst-case scenario, cadmium, which can cause kidney problems, would exceed the US reference dose by 5%, but would not exceed the Health Canada criterion. At the request of the Institut national de santé publique du Québec, the Ministère du Développement durable, de l’Environnement et des Parcs is considering introducing additional restrictions on FRM utilization to ensure the US reference dose is never exceeded in the most highly exposed people. The proposed measures are currently the subject of consultations. The Institut national de santé publique du Québec also warned of a theoretical long-term risk in dioxins and furans for highly exposed farmers (intensive and simultaneous use of four FRMs with high contaminant concentrations for 100 years, consumption of products produced on the farm, etc.). However, in the worst-case scenario, the additional estimated risk of cancer is relatively low (1 in 2500 chance to 1 in 435 000 chance among highly exposed farmers, according to the risk estimator used by the INSP). Moreover, the probability of high exposure in farmers is very low, notably because the dioxin and furan content of the main FRMs actually spread in Québec is well below the permissible limits.

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Q: The reclamation criteria may be very restrictive, but are they actually respected on the ground?

Photo MENVA: There are three types of regulatory violations: application of residuals without a certificate of authorization, application of residuals that do not meet the quality criteria (contaminant concentrations) and noncompliance with spreading conditions and limits.

According to the available data, nearly 100% of paper mill sludge spreading is carried out under a certificate of authorization. On the other hand, a not-insignificant amount of septic sludge is spread without being authorized, either through direct spreading or application following disposal into slurry tanks. This practice is not only illegal, but it is also dangerous, because septic sludge contains pathogens and has not undergone the required treatment. The Ministère du Développement durable, de l’Environnement et des Parcs and several member federations of the Union des producteurs agricoles du Québec have published non-scientific articles sensitizing farmers to the associated risks.

In an independent quality control of nearly 30% of residuals spread with authorization on agricultural land, the Ministère du Développement durable, de l’Environnement et des Parcs found that all of the residuals sampled met the minimum quality criteria, and the majority of analyses performed by plants and municipalities were reliable. The findings are to be published in a detailed report. Eight other FRMs were also submitted to an independent quality control by the Bureau de normalisation du Québec, and certificates of compliance were issued to all of the producers concerned.

In the controls performed by the Ministère du Développement durable, de l’Environnement et des Parcs, noncompliant spreading practices resulted from failure to comply in full with some of the conditions and limits; for example, the minimum distance from wells and ditches, not spreading malodorous residuals on the weekend, etc. In some cases, the noncompliance was attributable to negligence on the part of the person spreading; in others, the responsible agronomist had neglected to inform the farmer properly. To remedy these problems, the Ministère is contemplating increasing on-the-ground controls and sensitizing farmers’ representatives and the Ordre des agronomes to the importance of complying with spreading conditions and limits, the same as for manure spreading and pesticide use.

Q: Should BNQ certification be required for all FRMs?

A: To date, eight fertilizing residuals have been certified by the Bureau de normalisation du Québec (BNQ), including six liming materials and two types of compost. Together, they represent around 10% of all FRMs reclaimed. BNQ certification of FRMs is a progressive approach on the world scale, and one with which the Ministère du Développement durable, de l’Environnement et des Parcs and the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation have been actively associated since 1993. However, some residuals remain difficult to certify, such as those produced in limited quantities. Therefore, their spreading still requires authorization from the Ministère du Développement durable, de l’Environnement et des Parcs.

Q: Can FRMs be used in organic farming?

A: The Ministère du Développement durable, de l’Environnement et des Parcs considers land application of FRMs to be safe and in keeping with the principles of sustainable development when carried out in accordance with the Québec criteria. However, certain organic certification bodies may prohibit FRM use, as they have done with synthetic fertilizers and pesticides. Farmers who have or wish to obtain organic certification should therefore contact the certification body to inquire about FRM application.

Q: Can FRMs be spread after October 1?

A: The main risk associated with FRM application in the fall is nitrogen leaching into watercourses or groundwater. That is why spreading in the fall is permitted only for FRMs with a lower ammonia nitrogen content than solid and liquid manures. Residuals with a similar ammonia nitrogen content to manure may be applied only during the growing season. Spreading conditions and limits are also very stringent.

Q: Can municipalities adopt a by-law restricting or banning the use of FRMs?

A: Actually, some municipalities have adopted by-laws banning or restricting the use of FRMs within their territory. However, there has been some debate over the legality of such by-laws given that the Ministère du Développement durable, de l’Environnement et des Parcs oversees the environmental aspects of FRM reclamation. The courts have not yet ruled definitely on the matter. Nevertheless, municipal managers must see to it that these by-laws do not compromise the waste reclamation objectives imposed on municipalities by the Québec government and do not go against user rights.

Q: Shouldn’t the issue of agricultural utilization of FRMs be debated publicly?

A: In 1996, the Bureau d’audiences publiques sur l’environnement du Québec (BAPE) conducted vast consultations on waste management. It even devoted separate sessions to composting and FRM spreading. The final report highlighted the need to restrict landfilling of residual materials and increase reclamation in various forms. In response to the BAPE’s recommendations, the Québec Residual Materials Management Policy 1998-2008 sets reclamation objectives and calls for the development of agricultural utilization and composting. In 1998, the Ministère du Développement durable, de l’Environnement et des Parcs submitted its FRM reclamation criteria to its main partners, including the Union des producteurs agricoles and the Ministère de la Santé et des Services sociaux (MSSS), for consultation. Acting on their recommendations, the Ministère du Développement durable, de l’Environnement et des Parcs made substantial changes to the criteria, and is currently considering making further changes to give the criteria a more permanent character. To that end, the Québec government held consultations on the principle of agricultural utilization and the reasons underpinning its reclamation criteria.

Q: When all is said and done, what are the primary risks associated with FRM use?

Every human activity involves some degree of risk. That being said, the risks inherent in agricultural utilization of FRMs would appear to be relatively low in Québec. The primary risks arise from illegal practices, particularly unauthorized spreading of septic sludge. As for odours, improvements have been or will be made to ensure that FRMs do not create a nuisance for neighbours.

For further information, contact the Ministère du Développement durable, de l’Environnement et des Parcs information centre

Telephone: Québec City (local calls), 521-3830
Elsewhere in Québec, 1-800-561-1616
Fax: (418) 646-5974
Web site:

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