Agronomic utilization of residuals

Agronomic utilization of residuals : making the most of residues

• Background
• Industrial and municipal residues
• The advantages
• Quality control
• Odours
• Residuals and manure management
• For information

The use of fertilizing residuals (FR) in agriculture is by no means a recent phenomenon. Québec’s farm producers have long been using manure and harvest residuals as fertilizers on their farms. The spreading of other types of residuals, such as wood ash and fishing waste, has been recommended and practised for over 100 years, since the turn of the last century. Closer to home, bone meal, animal flour and compost are used extensively as fertilizers by professional and recreational gardeners.

Over the past twenty years, new residuals with useful properties have become available and there has been renewed interest in residual recycling. The materials in question include sludge (also known as biosolids) from municipal and industrial wastewater treatment plants, cement kiln dust, wood ash and compost. Their use, especially in agriculture, is a logical carry-over of Québec’s water and air clean-up efforts and initiatives and the collection of source separated organic waste. The agronomic use of FRs has therefore been included in the Québec Residual Materials Management Policy, 1998-2008. This policy promoted cost-effective alternative environmentally-friendly recycling methods that create jobs.

The advantages

There are three main benefits to recycling residuals. First, farm producers have access to new fertilizers and soil conditioners that help improve crop production, reduce costs or promote soil conservation. Second, by recycling residues that contain trace elements and which comply with the Ministère’s contaminant guidelines, industries and municipalities reduce the cost of managing and eliminating some of their waste. The environmental benefit of this type of nutrient recycling is that fewer resources are wasted and less waste goes to landfills or incinerators. An estimated 2 million tons of quality residuals therefore do not go to disposal sites every year, which reduces emissions of hundreds of thousands of tons of greenhouse gases. Just over one-third of these residuals are composted before being spread.

Fertilizing residuals that can be spread have important fertilizing or soil conditioning properties. Research carried out in Québec by various groups, including universities, the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation, Agriculture, Agri-Food Canada and industry, has shown that these substances positively benefit crops and soils. These findings confirm the results of research in the U.S. and Ontario, where residuals have been recycled for many years.

For practical purposes, the cost of FRs is determined on the basis of its ability to replace inorganic fertilizers, organic matter in livestock manure or commercial lime. For example, the average estimated value of some wood ashes is $45 per ton due to its nutrient value (P-K) and liming capacity¹. Papermill biosolids contain less potassium, but more nitrogen. Their use may significantly increase corn yields, for example, and improve soil humus levels.

Fertilizing residuals can be used in a number of different ways – for example, fertilizing and amending soils in agriculture, horticulture, forest management, revegetating degraded sites, etc. In some cases, the waste is composted first to eliminate odours, destroy pathogens and subsequently produce an “all-purpose” product.

[1] Hébert, Marc and Bruno Breton. 2008. Recyclage agricole des cendres de bois au Québec - État de la situation, impacts et bonnes pratiques agro-environnementales. Agrosolutions 19:18-33.

Quality control

The simple fact that a residual has agricultural value is not enough for the Ministère du Développement durable, de l’Environnement et des Parcs to authorize spreading. Residuals must meet a range of environmental quality guidelines that are among the most stringent in the world. Products must also be analyzed regularly. Residuals that are spread on crops destined for human consumption require an added level of quality control. This additional inspection is performed either by the Bureau de normalization du Québec (BNQ) or by a testing firm certified by the Centre d’expertise en analyse environnementale du Québec (CEAEQ).

In Québec, spreading municipal biosolids to fertilize crops destined for human consumption is prohibited, including in vegetable gardens, unless the biosolids have been certified by the BNQ to be compliant.

In addition to mandatory quality control and a ban on spreading over certain types of crops, agricultural recycling of FRs must be carried out under the supervision of an agrologist and in compliance with regulatory guidelines and best management practices. For example, FRs or manures cannot be spread within 30 m of a well or 3 m of a watercourse. In many cases, an authorization certificate is required before spreading can begin. The Ministère also performs on-site inspections when FRs are used².

If you have any doubts about the source or the quality of the products proposed, contact one of the regional offices of the Ministère de l'Environnement et de la Lutte contre les changements climatiques.

Odours

Some residuals emit very little odour. This is the case of wood ash, cement kiln dust and mature compost. Other organic residuals, however, may be malodorous and therefore must undergo treatment to reduce odour or are subject to stringent storage and spreading requirements, which are often stricter than those for farm manure. Neighbours of a spreading site must be informed before spreading begins and setback distances to neighbouring homes must be observed. A municipality may also prohibit manure and residuals from being spread for a maximum of 12 days each year, particularly during the summer.

Residents who, despite of all these preventive measures, experience inconveniences as a result of odours can contact one of the regional offices of the Ministère du Développement durable, de l’Environnement et des Parcs.

In 2007, an estimated 1 million tons of residuals were spread over cultivated land in Québec, compared to 30 tons of solid and liquid farm manures. Residuals accounted for fewer than 2% of the phosphorous input to farmland, compared to 35% for inorganic fertilizers². There is consequently no competition between FRs and manures. The competition is instead from inorganic fertilizers. 

Some residuals that are low in phosphorus and nitrogen, such as liming de-inking papermill residuals and cement kiln dust, also have properties that complement manure and inorganic fertilizers. These FRs are used mainly as organic amendments of replacements for agricultural lime.

Other residuals that are richer in phosphorous and nitrogen, such as papermill and municipal biosolids, have properties similar to manure. They are used in priority by crop-producing farms (corn, potatoes, etc.) that do not have easy access to manure or that are experiencing soil deterioration problems (due to a lack of organic matter).

In 2007, farm producers spread industrial and municipal biosolids over approximately 2.8% percent of all cultivated land in Québec.

[2] Hébert, Marc, Guillaume Busset and Elisabeth Groeneveld. 2008. Bilan 2007 de la valorisation des matières résiduelles fertilisantes. Ministère du Développement durable, de l’Environnement et des Parcs. 14 pages.

For information

To submit a project for use of fertilizing residuals, or for more information regarding guidelines and to obtain reference documents, please contact your nearest regional office of the Ministère.

You may also contact the reception and information service of the Ministère or consult our website.