Pesticides, applied as and when necessary, are a beneficial and generally accepted agricultural reality. Pesticide rinsate, however, which is often disposed in a dedicated field or strip of land, is a lot more problematic.

Despite being diluted via rinse water, rinsate exposes the ground to significantly higher concentration of pesticide due to the volume of material dumped in a small area. This can reduce soil fertility of the exposed area, can lead to pesticide run-off/leaching, and may one day soon prove problematic from a public relations perspective.

Lethbridge-based Agriculture and Agri-Food Canada research scientist Dr. Claudia Sheedy has a simple, proven, relatively new-to-Canada solution: pesticide rinsate biobeds that contain and naturally degrade pesticide residue.

Currently, Sheedy has research facilities across the country testing biobeds in various farming cropping systems. Whether via legislation or producers’ choice, biobeds may soon be reality on many Canadian farms.

“Pesticide rinsate is that thing no one talks about, but farmers don’t like it either. No one likes unnecessary pesticides in the environment. The issue is that once you dump the rinse water from your tank, you have no control over where that rinsate goes,” says Sheedy. “The biobed approach works because it’s practical, it’s not too expensive, it’s simple and effective, and it helps manage rinsate disposal.”

A biobed is a lined, waterproof, below-ground pit or above-ground box designed to remove pesticides from sprayer rinsate. Filled with a substrate of straw or wood chips, compost and/or peat plus soil, the biobed contains the rinsate and provides an ideal habitat for naturally-occurring soil microbes and bacteria to break down the pesticide residues.

“Naturally present bacterial and fungal communities seem to thrive after rinsate application. The majority we could identify are not known to be pesticide degraders, so there is a lot of research potential there. The more you apply rinsate, the more the communities thrive because it becomes their source of food,” explains Sheedy.

Depending on the size of the sprayer, collection can occur via a collection platform/pad or through a V-shaped trough. Thwe rinsate is pumped into a collection tank then slowly drips onto the biobed surface. The most effective biobeds are two-cell systems where effluent percolates to the bottom of an initial biobed then gets pumped to the top of a second biobed.

A biobed can effectively manage 10 litres of rinsate per square metre per day. Translated to a 100-day growing season, a single square metre of biobed can process 1,000 litres of rinsate per year. According to Sheedy’s research, the liquid at the bottom of the second bed contains between 90 and 98 per cent less pesticide than the original rinsate applied to the top of the first biobed.

“We seed the surface of both biobeds with grasses,” says Sheedy. “The first biobed, nothing grows on it at all. But on the second biobed, there is a lot of growth. It is a great way to visually see the effectiveness of the system.”

Pioneered in Sweden several decades ago and now numbering at least 3,000 across Europe, biobeds are only now gaining attention in Canada. Currently, Quebec leads the charge approximately 17-20 biobeds operational in both experimental and private farm capacities. Interest is slowly growing in other provinces. There are currently five experimental biobeds in operation across the Canadian prairies and two new ones coming at orchard and vineyard research stations in BC and Quebec in the spring of 2019.

Sheedy and Farming Smarter are awaiting a research funding decision to construct a biobed at the AAFC-Lethbridge experimental farm. If funding is approved, the project’s primary objective is to test a trough system adapted to sprayers with large booms. This biobed, with an existing one already on site, would allow management of 100 per cent of the pesticide rinsate produced at the farm.

Though Sheedy says biobed technology is ready for on-farm implementation today, she intends to continue biobed research from various angles. Top priorities include researching exactly which bacteria are most effective at consuming which pesticides; whether microbial inoculants may be useful to manage certain harder-to-degrade pesticides (like clopyralid, bentazone and imazethapyr); and whether more frequent fungicide-based rinsate applications is detrimental to the biomix’s bacterial communities.

Several European countries mandate biobeds. In Canada, Ontario may legislate their use. Whether (or when) Canada opts to follow Europe’s lead, the most cost effective time to install a biobed may be now, since CAP funding in certain provinces may support a significant portion of a biobed’s $10,000- $12,000 installation cost.

“I think it’s just a matter of time before they are common on Canadian farms. Our goal has always been adoption by growers. I am glad that the research we are conducting on pesticide rinsate biobeds serves our growers’ needs,” says Sheedy.

Interested in more information? Check out AAFC’s biobed construction, operation and maintenance manual at: