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Cleaning up the leftovers

AAFC has prepared a comprehensive manual on how to use “biobeds” to process pesticide sprayer rinsate

Despite careful calculation to mix just the right amount of pesticide to cover a field, there’s sometimes that little bit left over, or the rinsate which gets dumped onto a grassy or non-crop area, which can harm the environment. Up to 80 per cent of contaminants found in water bodies trace back to farms, according to Agriculture and Agri-Food Canada.

“If there’s groundwater and surface water nearby, that’s where contamination issues can happen,” says AAFC research scientist Claudia Sheedy.

To help farmers manage the problem, AAFC is promoting biobeds, a pesticide disposal system which has proven successful in Europe. It’s prepared a comprehensive manual on how to install them, as well as offering some assistance with installation.

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“We’re using the microbes existing in soil to degrade the pesticides, but in a biobed everything is contained so it doesn’t go anywhere. It’s a much safer manner to get rid of the pesticide residues,” says Sheedy. “The biobeds were built to deal with pesticide rinsate from sprayers, mostly. That’s what we are targeting.”

Biobeds can treat herbicide, insecticide and fungicide rinsates separately or in mixtures. They contain a mix of topsoil, compost and straw to absorb and then break down the pesticides to the point where they pose no further threat to the environment.

In June, AAFC released a manual on biobed operation and installation, based on four years of laboratory and field studies and three years of testing the proposed design in Saskatchewan and Alberta, as well as on European experience.


The first biobed was built in 1993 by Göran Ohlsson at his farm in southern Sweden. Sheedy estimates over 3,000 biobeds are now in use in Europe. They appeared on Canada’s radar back in 2001, when they were brought to the attention of former AAFC spraying specialist Tom Wolf by well-known EU agricultural consultant Eskil Nilsson, who took him to some installations in southern Sweden.

“Tom deserves all the credit for bringing biobeds to Canada and beginning research on their application for our climate,” says now-retired AAFC water quality engineer Larry Braul.

“On return to Canada, we recognized that this was an idea worth investigating and began to apply for funding,” says Wolf, now president of Agrimetrix Research & Training. Initially rejected by the Agriculture Development Fund (ADF) in 2004, the Pest Management Centre provided a small grant for proof-of-concept research in 2007.

Plants growing on top of a biobed remove water through evapotranspiration and can support microbial growth.
photo: Tom Wolf, Agrimetrix Research & Training

“We used the grant to conduct lab-scale work to see if the biomix can accelerate the breakdown of pesticides. We then built some field biobeds and expanded the range of products tested,” Wolf says.

Funding from Bayer CropScience in 2009 led to the building of the first commercial biobed in Canada at AAFC’s research site at Indian Head, Sask., followed by three more biobeds in Saskatoon and Indian Head in 2010.

Adapting to Canada

When Braul and Sheedy co-led the subsequent project to develop a Canadian biobed, they found European models needed modifying to take into account Canada’s climate differences.

“The most significant factors to adapting the biobed to the Canadian climate were addressing the heavy rainfall and the cold climate,” says Braul.

The heavy rainfall issue was addressed by testing the impact of rain on biobed efficiency and providing controls to divert rainwater from the collection pad and prevent overtopping of the storage tank.

By diverting rainfall away from the biobed with a diversion valve, flooding of the storage tank was prevented.

“For the case where the diversion valve is not activated and an extreme rainfall occurs, the float system in the storage tank provides redundancy by activating a pump at high water levels and pumps excess liquid onto the biobeds, thereby ensuring that the storage tank does not overtop,” Braul says.

Pesticide rinsate is stored in a tank, moved to the biobed for biological breakdown, and finally to a vegetative bed.
photo: AAFC

Braul says that in Canada’s cold climate, biobeds may not thaw until the middle of June, preventing use in spring and reducing the degradation of pesticides. The team addressed the problem by adding a heating coil to raise the temperature of the biomix in spring.

“This can be done using either electric heat tape or solar-heated liquid, and is relatively inexpensive — about $30 of electricity,” Braul says.

By raising the temperature to 25 C in early spring, the biobed is fully functional at an early date and enhances the micro-organism activity, Braul says. The warmth of the sun and the air maintains the temperature once the biomix is heated in spring.

AAFC tested single and two biobeds in series, with results showing a single biobed removed 90 per cent and two in series usually over 98 per cent of the pesticides. AAFC also found that challenging pesticides were often removed at a higher rate in the second biobed. Sheedy says two units are recommended for farms that use a lot of pesticides and generate a lot of rinsate.

Assistance available

Wolf says biobeds are also used in parts of Central and South America, while Canada has six research sites in the West and 17 more in Quebec.

“Bottom line, though, is that farmers have not been building biobeds and the current installations are at government sites. With the recent publication of an excellent biobed manual by AAFC, this could change,” says Wolf.

Although Canadian adoption is slow, Sheedy expects adoption to gain ground, due to the manual and assistance from the Canadian Agricultural Partnership program. Pesticide rinsate biobeds are eligible for funding in several provinces under that federal-provincial co-funding program — up to $10,000 — which covers the majority of the cost of building a biobed, Sheedy says.

“Our current designs are between $8,000 to $12,000,” she says, noting the major part of the cost is the cement collection pad that sprayers drive onto.

Most biobeds only need winterization in late fall, which amounts to removing the pumps, timers and tubing which might be susceptible to freezing and cracking, Sheedy says.

In the spring, the biobed is topped up with biomix, a mixture of either chopped straw or wood chips with topsoil and compost.

The mixture’s longevity in Canada isn’t fully known, but in Europe the recommendation is to change the biomix entirely after eight years. Under colder Canadian climate conditions, longevity should be longer, Sheedy estimates. AAFC’s oldest biobed is six years old and its performance hasn’t decreased, still removing 98 per cent of what’s applied to it, she says.

Once biomix reaches the end of its lifespan, AAFC says disposal includes composting for one year before spreading it with a manure spreader at the lowest possible application rate. Composting should be carried out in an area that is away from any water body or well to prevent any contamination issues, AAFC says.

The manual titled A robust biobed design for managing pesticide rinsate under Canadian conditions is available online — visit AAFC’s website and search for “biobed.”

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