Biodegradable Plastic Mulches No Longer Allowed in Canadian Organics…..What Now? 13

After years of using biodegradable biobased mulch films (or biofilms for brevity), in early 2015 certified organic farmers in Canada were told that biofilms would no longer be considered an allowable input.

Farmers from across the country were understandably upset and confused.

Biofilms offer benefits in weed control and soil warming.  And they biodegrade within 2 seasons, eliminating the need to be picked up. Every ecologically-minded farmer who was using or wanted the benefits of regular plastic mulch, was happy to avoid adding more waste to the landfill.

When I first learned about non-GMO, corn starch-based biofilms, I was excited about the potential.

I had never been a fan of plastic mulch but neither was I happy to frequently cultivate my soil, which decreased my capacity to build soil organic matter and store carbon.

In our first season on our new farm, converting hay fields to beds of vegetables, using biofilm kept the plentiful weeds from taking over and helped us achieve enough yield to make a living.

Until the spring of 2015, Ecocert, our organic certifier, allowed us to use it.

So, what happened?

Well, it turns out that none of the biofilms currently available in the marketplace are 100% bio-based (which is the requirement in both the Canadian Organic Standard (COS) and the U.S. National Organic Program Standard) but rather contain only 10-20% biobased material.

The rest is made up of polymers from fossil fuels (petroleum and natural gas), dyes, minerals, and sometimes heavy metals.

There are no 100% biobased biofilms, nor are there any expected to be available in the near future (despite what I’ve heard from some salespeople).

On our farm, we started using a biofilm called BioTelo and then moved to a product called Bio360. Both of them include a material called Mater-Bi, produced by a company in Italy called Novamont. Mater-Bi is made with non-GMO cornstarch, but also contains proprietary, biodegradable ingredients from renewable, synthetic or mixed sources. And it’s those extra ingredients that are the problem.

The revised COS published in November 2015 authorizes the continued use of these biofilms—including tilling them into the soil after use—until 2017 only (to allow farmers time to figure out their new management plans).

As a result, the search is on for alternatives to biofilms at certified organic farms across the country.

We’d been thinking about this topic throughout last year’s season, and spoke with  many other farmers about it. Most of the other organic farmers I’ve spoken to who have been using the biofilms are still unsure of how they will replace their use. Here are some ideas we’ve considered or heard from other farmers:

Pulling up the biofilms at end of season

Last year (2015), we still had leftover rolls from the prior season so we covered some beds with biofilm and removed it by hand (and rakes). This could be an option some people might choose every season. But, what do you do with the biofilms you picked up? Throw them away like you would with regular black plastic, though that is an expensive choice since biofilms are pricier than black plastic mulch.

Philosophically, trashing biofilms over black plastic might seem attractive simply because the films are compostable under ideal composting practices and so they might break down in the landfill (though that is not an ideal composting situation). Truthfully, it is not easy to pick them up. Regular black plastic takes time to pull up and can definitely break apart but biofilms start breaking down within a single growing season and as soon as you grab some, bits break off.

Regular Plastic Mulch

While we’ve never purchased black plastic mulch, we were given a roll with our mulch layer and are used it last fall for overwintering onions. Black plastic mulch and black biofilms are comparable in terms of weed suppression, soil warming, moisture-conservation, and reduction of nutrient leaching.  Since many organic farmers have purchased expensive, mechanical mulch layers in order to lay their biofilms, the easiest thing for them to do is switch to regular plastic mulch (or sell their mulch layers).

Black plastic burdens landfills. Some landfills have stopped accepting plastic mulch while in other regions recycling programs have been created for black plastic waste (though it’s still cumbersome and expensive to transport). There is also the fact that some soil and crop residues are removed with the mulch.  While the volume of soil and organic matter removed may seem small on any given sheet of plastic, it definitely adds up and works against what organic farmers are trying to do, which is build their soils. This plastic not only ends up in landfills (which would be the ideal scenario for it), it also frequently gets burned (air pollution) or gets blown or washed away (80% of plastics in oceans comes from agriculture).

Landscape fabric/Geotextile

In previous years, we’d only used landscape fabric between widely-spaced crops like tomatoes and winter squash. The narrow space between the 2 sheets of fabric serves as the row, which we mulched heavily with compost to inhibit weeds. This system has worked well. There was only one weed to pull from our winter squash field last season!

We knew of many other farmers who used it for tighter spaced crops with success by burning holes at the proper spacing (cutting it leads to unravelling of the woven plastic) which we tried this year for cut flowers.

Increased use of landscape fabric is likely on our farm though we have heard concerns about plant diseases remaining in the landscape fabric since it is reused each year and difficult to sanitize.  A great benefit to the landscape fabric is that it breathes and rain can be absorbed in the soil underneath it. If you take care of it, it can last for 10 years or more.

Rolling/Crimping Winter Rye

We’ve been interested in the idea of rolling or crimping cover crops to create mulch.

As small, diversified farmers, it doesn’t make a lot of sense for us to invest in a roller crimper to attach to the back of our tractor, especially before knowing how this might fit into our overall system.

So, after hearing the idea from a friend in the States, we tried using our tractor-mounted rototiller as a roller crimper. The idea is to use the rototiller without the PTO turned on and just ground drive the rototiller over the rye after pollen shed (when it can be killed by crimping the stems). 2015 was our 2^nd season trying it.

We found we needed to go over the rye twice about a week apart to kill it (two passes is also typical for a roller crimper).

We ended up having too many weeds like dandelion that came through the mulch so decided not to plant into it but this was due to our initial bed prep prior to seeding the rye rather than it not being a worthwhile activity.

This would really only work in our region (Atlantic Canada) for late-season plantings since the stage where rye can be killed happens later in the season (early-July) in our region.

It also doesn’t contribute to warming the soil at all; in fact, it keeps the soil temperature cooler.

Mowing Winter Rye

This year we also experimented with mowing some overwintered rye after pollen shed.

It died off and left a nice residue into which we transplanted fall kohlrabi and cauliflower. We transplanted half our planting into a regular raised bed that had been tilled. It was not easy to transplant into the mowed rye and we needed trowels to create the holes for the transplants. The plants and yields were later and smaller overall in the no-tilled beds. I think next time we would increase the spacing of the plants in the no-till beds (from 18 inches to 24 inches or more).

We’re also planning on trying to solarise some overwintered rye next spring while it’s still short (with clear plastic though we may also use some black silage tarp to see how they compare) and then plant into that once the rye has been killed.

Paper-based mulches

We were interested in a product called Weed Guard Plus, which is a paper-like product and is the only OMRI (Organic Materials Review Institute) approved mulch in the U.S.

The soil warming properties are lower than with black or clear biofilms but it does inhibit weeds.

However, the company Weed Guard Plus has not applied for their product to be certified as allowable in organic agriculture in Canada due to the added costs and paperwork required. They don’t think the potential Canadian market is worth it at this time and their current Canadian distributors haven’t asked for them to certify it.

Another downside of this product is the cost which is higher than biofilms. The rolls are also heavier and so costs of shipping to Canada would also be higher.

I’ve heard conflicting reports on how easily the paper mulch can be layed with a mechanical mulch layer with some saying it’s a challenge and others saying it works fine as long as you take pressure off the wheels.

We’ve trialed some this year in a perennial flower bed (since flowers are not approved for organic certification in Canada anyway). It’s too soon for us to say whether we like it or not yet.

If you think this is a weed management tool Canadian organic farmers should be able to use, I encourage you to contact both the company (Weed Guard Plus) and the Canadian distributors of it (Vesey’s) and tell them you want it to be certified as allowable in Canada!

Mulching with other materials

Many people mulch with straw or hay though there are downsides like keeping the soil cool (which can be an upside but not as a replacement for biofilms), being a haven for slugs and rodents, being inaccessible or expensive to find organically and being either labour-intensive or needing specific machinery to apply.

We have used compost to strip mulch single rows between landscape fabric for crops that are planted farther apart (winter squash, summer squash, melons, tomatoes) which worked really well for keeping the weeds down.

Despite it being a pricier and more labour-intensive practice, we are very interested in increasing our use of compost as mulch to replace biofilms. The benefits extend beyond weed management and increased soil temperature to increasing soil organic matter and providing opportunities for non-mechanized no-till (a la Singing Frogs Farm in California).

Discontinue Organic certification

I’ve spoken with some farmers who feel that biofilms are still the best option for their production system and that discontinuing their use would reduce the profitability of their farm business too much, in terms of labour savings with regard to weeding, and removing the plastic at the end of the season.

In order to keep using biofilms and to continue tilling it into the soil after use, these farmers are considering discontinuing their organic certification. There are some farmers in the U.S. who followed that path when they weren’t allowed to use biofilms, feeling that plastic mulch was less of an “organic” option on principle. These farmers tended to be direct-marketers who could explain to their customers why they felt using the biofilms was important to them and how it fit with their values.

Physical cultivation/weeding

This is of course the old stand-by.

And the use of biofilms hasn’t replaced the need to weed. There are still plenty of crops that are not being grown with mulches.

The reason so many farmers have been happy to use these mulches is due to the high labour or machinery costs of weeding and cultivating.

Organic farming has been criticized for its high use of physical weed control which disturbs the soil biology and organic matter (exposing carbon molecules to the air, where they combine with oxygen to create carbon dioxide). Many organic farmers have been trying to move towards reduced tillage systems.

Organic farmers have been using many weed management practices very successfully, including the use of cover crops, crop rotations, stale seed bedding, solarisation (clear tarps to burn weeds and weed seeds), occultation (black tarps to exclude light) and flame weeding. Biofilms and other mulches haven’t replaced the need for these techniques, rather they reduced the associated labour for certain crops.

Ultimately, for our farm, no single method or product is going to be able to replace the benefits we thought we had with biofilms- there are no quick fixes or easy answers.

Our goal is to produce nutrient-rich food for the human species while minimizing harm to other species. And that is not easy (the general food-producing systems of our world have mostly done the opposite). This is why organic food costs more and why it should cost more. We’re not taking the path of least resistance; we’re recognizing that this planet is only ours to respectfully share.

I originally wrote this article for and it was published in The Canadian Organic Growers Magazine’s Spring 2016 issue. TCOG (for short) magazine is a great magazine that you can either subscribe to online or as a print/paper copy. Check it out! This article was written as a follow-up to the first article I wrote on this issue originally published in the ACORN newsletter (and later published in The BC Organic Grower).