Qualified praise for biodegradable plastic mulch

We’re having a very busy time in the garden. Because of late cold weather followed by too much rain at once, all our transplanting has been delayed. We’re up-to-date in the permanent raised beds – we’ve planted out lots of lettuce, senposai, early cabbage, scallions, our first cucumbers and summer squash, and chard, tomatoes, eggplant, celery and okra. We’re also up-to-date on raised bed sowings of carrots, turnips, beets, snap peas, snow peas, bush beans, edamame and asparagus beans. But in the row-crop areas, it’s a different story. We have planted out our main-crop cabbage and broccoli, our “spring” potatoes and sown our first corn. We’re about a week behind on our big transplantings of Roma paste tomatoes, peppers, melons, sweet potatoes, and therefore watermelons. It’s also time to sow more beans, cucumbers and squash. But we’re getting to it as fast as we can!

We’ve added in late afternoon transplanting shifts, and some random evening weeding (which has helped us get the first round of carrot and beet thinning done). Yesterday I measured and flagged the areas for Roma tomatoes, peppers, melons, beans, edamame, watermelon, and sweet potatoes. I set out the mainline tubing for the drip irrigation and dropped the shuttles of drip-tape at the ends of the patch. I wrote about our drip tape shuttles a while back. They are part of our commitment to minimize our agricultural plastic usage by making our plastic stuff last. The shuttles let us fairly easily reuse the drip tape.

After running out the drip tape, flushing the lines, capping them off and testing (and fixing!) any leaks, next we’ll roll out biodegradable plastic mulch. This wonderful product has changed our lives! And yet we are not all firmly convinced it is an ecological choice. The language in the accessible information can be confusing.

We like using biodegradable plastic because it warms the soil, leading to much earlier crops, it keeps the weeds down for a few months, and then it falls apart, so we don’t have to remove it and add to the heaps of agricultural plastic trash. It’s especially good for vining crops like watermelons and sweet potatoes, because by the time the mulch disintegrates, the vines cover the ground and weeds have little chance. Why we qualify our praise is because it has been hard to find out what it’s made of, and what it disintegrates into. And for some, there’s that knee-jerk reaction to anything plastic!

Biodegradable is not the same as bioplastic, nor as bio-based. Bioplastics are a type of plastic made from biological substances rather than from petroleum products alone. Some are biodegradable, some are not. Wikipedia distinguishes two types of bioplastics 1. Oxo-biodegradable plastics (made partly from natural sources, with non-biological additives) – they break down into biodegradable materials;  and 2. Plastics made wholly or in part from vegetable material. The second type are often made of cornstarch or sugarcane, but could be made from other agricultural crops. Some biodegrade, others don’t (eg those made from sugarcane ethanol). I found the Wikipedia explanations confusing and some read as if they were funded by petrodollars: “It is difficult to see why . . . resources . . . should be used to produce them when the raw material for conventional plastics is so inexpensive and is available in unlimited quantities.” Really.

I found a European Factsheet on bioplastics which clears some of the confusion. There are conventional (petroleum-based) plastics and there are bioplastics. Bioplastics may be divided into three categories. The first is the bioplastics which are not biodegradable. The other two are biodegradable, and differ in whether or not they contain fossil-based materials or only bio-based materials. Our goal would be to get biodegradable bio-based materials.

The two most commonly available biodegradable plastic mulches in the US are Eco-One and Bio360  from Canada. Novamont, an Italian company, imports Biotelo, the original mulch film made from their product Mater-Bi.

Eco-One describes itself as Oxo-degradable. It claims “Environmentally sound degradation: Laboratory studies indicate that this degradable plastic breaks down into CO2, H2O and biomass without toxic residues. Degrades fully both above and below the soil.” It’s available clear (for encouraging early emergence of sweet corn) and black, including an extended lifespan version for those wanting a 5-6 month window before it degrades, rather than the usual 3-4 months.

Bio360 is made by Dubois. It’s entirely biodegradable, and made from Mater-Bi, a non-genetically-modified starch with vegetable oil resin. Mater-Bi® is a wide family of fully biodegradable bioplastics, sold in pellet form to the industry of bioplastic converters. Mater-Bi®’s ingredients consist of plant starches, “mainly corn starch, with fully biodegradable aliphatic-aromatic polymers from both renewable raw materials (mainly vegetable oils) and fossil raw materials. Mater-Bi breaks down into carbon dioxide and water, with no mulch residues in the soil.” (see also the Cornell University 2006, Biodegradable Mulch Product Testing). Ah! So even Mater-Bi contains some fossil raw materials. And of course, fossil fuels are used in the manufacturing process. Life is so full of trade-offs!

I found explanation of the chemistry from the Biodegradable Products Institute, as part of a 2012 petition to the USDA National Organic Standards Board to allow “Biodegradable Mulch Film Made From Bioplastics”.  The bioplastics they were petitioning for are not polyethylene like regular plastic mulch, but “polyesters, polymers formed by the reaction of a hydroxyl group and a carboxyl group. The natural world is full of ester linkages. Living cells and organisms have developed enzymes to hydrolyze the ester linkage. Examples of natural esters are fats and oils, where three fatty acid molecules are esterified to glycerol/glycerin; natural waxes, where long-chain alcohols are esterified to a fatty acid; and some natural flavors, such as banana flavor, n-amyl acetate, an ester of n-amyl alcohol and acetic acid.” Biodegradable bioplastic mulch film materials can contain carbon black to make the film black to absorb heat from the sun. Or titanium dioxide to create  white mulch, which can cool surface soil temperatures slightly, by reflecting most of the sun’s heat.

NatureWorks‟ PLA INGEO, Ecoflex® F Blend C1200, Ecovio® F Film and Ecovio® F Blend, Mirel™, were also listed in the petition as suitable Biodegradable Mulch Films made from bioplastics. In contrast, oxo-biodegradable materials were not included in their petition, because they did not fulfill the two criteria proposed to address the concept of “fully biodegradable plastics”.

The Organic Standards are inconsistent, as §205.206(c)(1) permits “mulching with fully biodegradable materials” but §205.206(c)(6) requires that “plastic or other synthetic mulches . . . are removed from the field at the end of the growing or harvest season.”

I’ve been buying from Nolt’s Produce Supplies in Leola, PA (717) 656-9764. They sell Bio360 BTB645 4′ x 5000′ for $345 plus shipping, and Eco-One E1B548 4′ x 8000′ for $243 plus shipping. They are a company that doesn’t use email or websites, and they’re closed on major Christian holidays, so don’t call then! Johnny’s sells 32′ lengths for $17.95. Robert Marvel sells whole rolls of Eco-One and Bio360 (call for prices).

The first biodegradable plastic we used was Bio-Telo, (Mater-Bi). Since then we have sometimes bought that and sometimes Eco-One. I had not appreciated the difference. Knowing what I know now, I’ll buy the Mater-Bi types in future, rather than the oxo-biodegradable ones.

Next time I’ll write about how we set out biodegradable mulches without he use of any machines. Sorry for the delay in posting. I’m working on making improvements to my website, honest!

I wrote this article for ACORN’s summer 2015 newsletter and am now republishing it here.

At the end of March of this year (2015), we found a memo in our inbox from Ecocert (the organic certifying body that we are certified with). In this memo, we were told that we would no longer be able to use the biodegradable plastic mulch (made with non-GMO corn starch) that we had been using unless we removed it after use. We were surprised and concerned. It was definitely a little last-minute! We still had leftover rolls of it at the farm from last season and had made our order for this season back in December (when we do a lot of our inputs purchases). And the removal part….it’s pretty tough to completely remove something that biodegrades as it’s in use.

Bryan and I have been using biodegradable plastic mulch (which I will refer to from now on as biofilm to reduce typing) since the first year we started Broadfork Farm. As small farm operators, we have appreciated the reduction in our time spent weeding in particular. But there are other benefits to using plastic mulch, like warming the soil and retention of moisture in the soil. With our deep feelings of stewardship for the soil, we have also liked how we have been able to keep more of the soil covered during the season (with the biodegradable mulch in the beds, our pathways have been maintained in living mulch that we mow). Soil left bare tends to create its own “cover” of a dry, dead, erodible soil layer.

We knew that, as a manufactured product, biofilm wasn’t the perfect solution in our utopian organic vision. But it was a solution we preferred to regular plastic mulch (with the required pulling up at the end of the season and taking to the landfill) or frequent cultivation.  There are of course other mulches like straw or leaf mulch but they didn’t fit in as well with our whole system (but rather have fit in with some crops in certain instances when we could access sufficient quantities without prohibited substances).

We had often talked about the fact that we didn’t think we could have made 100% of our household income from our farm from our first year without the use of biofilm. We even listed it as one of our 5 favourite market gardening tools! Especially in our first year while we converted hay fields to vegetable fields…while growing vegetables. The sod clumps that we’d overturned were too lumpy to be able to use a wheel hoe (or any other kind of hoe for that matter) for weeding.

So, after receiving the Ecocert memo, I contacted other people involved with the Organic Standards and asked, what’s up with this? It turned out, that our Canadian Organic Standards had never allowed the use of the biofilms (without removing from the field after use) that are currently available in the marketplace. But there was a lot of confusion around this, both by farmers and certifiers. I think the confusion stemmed from the language of the Standard (very Standard-y) and the uncertainty of exactly what substances each biofilm on the market contains.

This is what the Standards said:

Fully biodegradable films: permitted without removal if they do not contain substances prohibited by par. 1.4.1 of CAN/CGSB-32.310, Organic Production Systems — General Principles and Management Standards.

I think it was clear to everyone that the biofilms couldn’t contain GMOs or pesticides. And the ones organic farmers were using don’t contain these.

Many organic farmers had happily been using this input for years and so, when the memo came out right at the beginning of the growing season, it was a big shock. People involved with the Crops Permitted Substances List (PSL) working group of the Organic Standards Technical Committee, the Standards Interpretation Committee (SIC), and the Canada Organic Office (COO) at the CFIA all started trying to figure out an appropriate and fair solution.

So, why aren’t biofilms allowed? Well, all of the biofilms on the market currently contain a certain percentage of petroleum source materials (which are prohibited) that seem to be referred to as raw fossil-based ingredients (by manufacturers). The biofilm that we had been using, while having the lowest percentage of petroleum source materials of any other biofilm, is still around 20%. I didn’t like learning that. And I was disappointed it wasn’t clearly expressed by the companies that were manufacturing and selling these biofilms. I had thought the biofilm we were using was actually 100% non-gmo corn starch.

Then there is the issue of biodegradability. Most farmers who have used these biofilms know that the biodegradability varies (so the ‘fully biodegradable’ part of the above Standard was a tricky one). It varies from farm to farm, field to field, season to season. In particular, it varies based on the life in the soil, the soil temperatures, and the soil moisture. There has been a bit of research done on this but not enough. The primary ingredient in the biofilm we’ve used, the corn-starch material Mater-Bi, is shown to be compostable in ideal composting situations but that’s not the same as using it on top of the soil in highly variable field conditions.

As I was trying to learn as much as possible about this input, I realized that there are currently too many unanswered questions. Like what happens to all the bits (even the bits we can’t see with the naked eye) that don’t fully biodegrade? Are they contributing to those floating garbage islands in the ocean? Are they being taken up into the web of life through food chains (insects, birds, mammals) and their materials concentrated? And to what effect? Are the microorganisms in the soil changing…adjusting to a new food source….and if so, is this harmless or harmful on the balance of life in the soil? Are there residue buildup issues we should be concerned with (the labelling always says “No toxic residues’ but what is this claim based on? Over how many years and with how much biofilm use? Is this claim unlimited?)?

With both the sustainability of farm businesses and care of the soil in mind, the Organic Technical Committee brought forward a revision to the 2015 Canadian Organic Standards. This is that these biofilms with the prohibited substance of petroleum products (all that are currently on the market, remember) will no longer be allowed unless removed from the field….but that, in order for farmers to figure out new systems without the use of these products…or, fingers-crossed, time for the manufacturers to figure out a way to change their products to be compliant….organic farmers will still be allowed to use the biofilms as they have been (i.e. tilling back into the soil) until 2017. And, for this 2015 season, since the newly-revised 2015 Organic Standards won’t come out until the fall, the Canadian General Standards Board has sent out a bulletin saying that this new Standard will be in effect for this season  as well (you can read that bulletin here).

As organic farmers, we are committed to being stewards of the soil. While we need all the help we can get with improved products and efficient techniques in order to provide ourselves a livelihood, as small-scale organic farmers, we realize that we are only the caretakers of this land for the tiny time period of our lifetime. This land needs us to consider our impact on the generations that follow ours. So, we are always researching, learning, and questioning what we thought we knew.

Bryan and I have decided that, beyond using up our leftover biofilm from last year (we cancelled the order we had made back in December after the memo came out), we wouldn’t use any more biofilm (unless the manufacturers make some serious improvements in the future). But how will we replace it’s benefits in our operation?

At this point, we’re thinking about increasing our annual use of landscape fabric (which can be rolled up at the end of each season and re-used for many years). This reduces our opportunities for living mulch in our pathways which we’ve really liked having…though there are always plenty of beds that don’t get any mulch at all (like beds of salad mix, carrots, salad turnips, radishes) that will still have the living mulch pathways.

We’ve also been experimenting with rolling/crimping rye and flail mowing rye and then planting fall brassicas (like cauliflower, broccoli, kohlrabi) into it.

Since biofilms haven’t been allowed on U.S. organic farms (but many farmers there have wanted to), there has been some thought and a little research coming from there on this topic.  Here are a few resources you may find interesting for further reading:

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