A better way to dispose of pesticide rinsate

Biobeds are an environmentally friendly way to break down pesticides in the rinse water flushed out of sprayers as well as leftover or unusable pesticides once they’re sufficiently diluted. You’ll find biobeds in Sweden and other European countries, but they haven’t caught on with farmers in Western Canada. Farming Smarter, an applied research group that works in agriculture in southern Alberta, is trying to change that.

A few years ago, Farming Smarter built a biobed at its research farm near Lethbridge, Alta. The organization now has a portable model on a trailer it took on the road this past summer. The goal is to illustrate to farmers how biobeds work and how they can be built relatively easily and inexpensively. It’s something Farming Smarter planned to do before now, but the pandemic got in the way.

“We were first showing it off right at the beginning of COVID and were getting quite positive reactions,” says Ken Coles, executive director of Farming Smarter. “A number of farmers actually expressed some interest in implementing one on their farms and there were some counties that were interested. Not everybody, for sure, but it seemed like we were starting to generate some interest.”

Unfortunately, that interest tailed off with the pandemic, which limited Farming Smarter’s extension program and the organization’s ability to meet face to face with people. As a result, “we haven’t had a lot of uptake in people actually taking the step to build their own,” says Coles.

The original idea was to showcase the mobile biobed at trade shows and lend it out to interested farmers and county officials, so they can use it as a model to build their own biobeds.

“We’ve had some good results and we really want to make sure farmers can start using them,” Coles says. “My philosophy has always been to practice what you preach. And if you do it yourself, you’re going to learn the ins and outs of it and be able to share that with farmers. One of the things we wanted to do is just show it’s not that hard to do.”

Farming Smarter received some funding from the Canadian Agricultural Partnership in Alberta to construct its first biobed in 2019. They referred to a manual developed by Agriculture and Agri-Food Canada to build it, but used salvaged materials wherever they could to keep costs down. The final cost was $5,000.

“Of course, you could spend lots of money on this, or you can be frugal, too. For us, we were frugal,” Coles says.

Farming Smarter built this mobile biobed to show farmers how biobeds work and how they can be constructed relatively easily and inexpensively.

Farming Smarter

The biobed was built atop a pad made from old pieces of concrete pulled from a junk pile. It consists of two holding tanks for the rinsate and two biofilter stages made from a couple of inexpensive tanks with the tops cut off. The stages, which use biological metabolization to convert pesticide chemicals into inert forms, contain a bio-mixture of soil and compost straw.

The first holding tank can hold up to a year’s worth of rinsate, which is gradually moved through the first stage using drip tape. Anything that’s left then goes into the second holding tank, and the process is repeated in the second biofilter stage. Farmers who would like to learn more about the biobed can watch a virtual tour at the Farming Smarter YouTube channel.

Farming Smarter’s mobile biobed is built much like the one on the Lethbridge research farm, just a smaller version.

“We tried to use all of the same fittings, the same pumps, the same drip tape,” Coles says. “We just used some different tanks to miniaturize the scale. All the tanks are smaller, other-wise everything else is exactly the same.”

Coles views biobeds as a good practice that can boost chemical safety on farms and as a way farmers can address public concerns about the effects of agriculture on the environment.

“For me, it’s just another level of responsibility we can demonstrate to the general public and whoever is interested — that we’re taking the right steps,” he says. “I think there are a lot of farm businesses that are very much interested in doing what’s right on their farms. I think there’s growing appetite for this type of effort.”

Coles is hopeful but he’s also realistic. He says he believes it will take time for biobed technology to gain popularity in Western Canada, and most likely some change in the regulatory landscape around pesticide disposal.

“Probably the biggest thing that’s going to motivate people is if there’s ever a policy implemented, and then you have to do something like this. It’s unfortunate, but those types of regulations are really what drive adoption,” says Coles.

“I think down the road, we’ve already seen it happening in Europe. There’s a good possibility this may happen here. But in the meantime, we hope to get some experience with them and have the proactive folks engaged and even counties start implementing them,” he adds. “We’re fortunate at this point that we have some time to get ahead of the game.”

Many ways to build a biobed

Tom Wolf is a sprayer expert at Saskatoon-based Agrimetrix Research and Training who says a properly constructed biobed system can contain 90 to 99 per cent less pesticide than was introduced, depending on the pesticide.

Wolf helped introduce the biobed concept to Canada in the 2000s when he was a research scientist with Agriculture and Agri-Food Canada (AAFC). He built biobeds as part of his research and has a how-to article on his Agrimetrix website, which you can find at the Sprayers101 website.

Wolf points out there are many possible variations of biobeds, from something relatively simple to others engineered to meet certain needs.

“You can dig a hole in the ground, you can use a plastic tub above ground, you can use them in sequence. There’s a lot of different ways of slicing and dicing this.”

Wolf says biobeds work best when there’s a central place that’s frequently used to fill and clean sprayers, such as an area set aside in a farmyard. He acknowledges many farmers find it easiest to rinse their sprayers in the field once they’re finished the job, rather than driving back to the yard. And, if it’s done properly, it can be safe to do so, he adds.

“The opportunity now to have a biobed on a farmyard has value because, let’s face it, every farmer that sprays has a spot on their yard where they do the filling and the cleaning and the rinsing and the dumping,” says Wolf.

“It’s usually not front and center. It’s often a place where after some quick evaluation they think it’s the right spot, but it’s usually not necessarily good either. It could cause runoff into a slough, pond, dugout or certainly groundwater,” he adds.

“It’d be much better if you did your cleaning on some kind of a containment pad. It could be concrete that’s bermed, or it could be just a membrane of plastic collecting rinsate that’s pumped into the biobeds. A little bit more infrastructure is required, for example, to bypass the system when it rains, but it’s certainly a preferred way.”

Wolf stresses farmyard biobeds should be placed somewhere with good drainage to reduce the risk of flooding. “The microbial population is aerobic. It will die if it’s waterlogged,” he says.

“Most biobeds will have a layer of this pea gravel in the bottom so that you can readily pump it out if it’s full of water,” says Wolf. Some biobeds will also include a top layer of grass or shrubbery to reduce the risk and a roof covering of some sort is recommended to avoid waterlogging from excessive rainfall, he adds.

This rinsate collection through is where sprayer operators at Ag-Quest’s research station in Minto, Man., dispose of leftover pesticides. The rinsate is then pumped into a 1,000-gallon seasonal holding tank.


Ag-Quest biobed

Ag-Quest is an organization that performs contract agricultural research at five field stations in Manitoba, Saskatchewan and Alberta. It constructed a biobed at its research station in Minto, Man., last year and plans to build more. Robert Doell, who is a project coordinator with Ag-Quest, says the move just made sense.

“We do a lot of research with pesticides, testing crop tolerance and product efficacy on various new products and formulations and uses. At each of our research stations we end up with a quantity of rinsate that has pesticides in it,” Doell says. “With increasing volumes, we were unhappy with our rinsate disposal — collecting and spraying it on field margins — so we set up a biobed at our Minto station.”

Doell says Ag-Quest managers at Minto studied the AAFC manual on making biobeds as well as articles on different methodologies and models from Europe before coming up with their own design.

The biobed is comprised of three, 1,000-litre totes, each filled with a bio-mixture of soil, peat and straw over a layer of crushed stone and separated by landscape fabric. A quantity of rinsate is pumped up to the top of the column each day and trickles over the material in the top tote, moving through them in sequence until it drains out of the bottom tote.

“Most of the literature will indicate that by running rinsate through a number of different vessels like we are — depending on what the product is — you can get rid of upwards of 95 per cent of whatever pesticide residues are left in there,” says Doell .

“We haven’t done any testing in terms of getting lab samples of the water sent away for analysis. But just on an anecdotal basis, the rinsate we collected had a strong pesticide odor and a color from various products.

The Ag-Quest biobed is comprised of three, 1,000-litre totes, each filled with a bio-mixture of soil, peat and straw over a layer of crushed stone. Rinsate is pumped into the tower from the seasonal holding tank beside it.


“Once we ran it through our three vessels, it came out the bottom as clear, odorless water. I wouldn’t assume that there are no residues in it, but visually and in terms of smell it appears to be a much safer or a much less obnoxious product. It looks and smells much better than what we were dealing with coming out of these sprayers,” says Doell.

“We’ll probably do a test on the exudate at some point, but we haven’t yet. (It’s a) vast improvement over past practices, so we’re happy with that right now, but we would like to get a handle on what’s actually happening,” Doell says. “We’re looking at instituting a similar system at the rest of our stations in the near future.”

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