Tag: Mater-bi

Qualified praise for biodegradable plastic mulch

Tomato transplants waiting in the cold frame. Credit Kathryn Simmons
Tomato transplants waiting in the cold frame.
Credit Kathryn Simmons

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.

Re-using drip tape, unreeling it using our shuttle and garden cart system. Photo credit Luke Stovall
Re-using drip tape, unreeling it using our shuttle and garden cart system.
Photo credit Luke Stovall

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!

Peak Watermelon Day?

This morning we picked 99 watermelons. I hope this is the peak day of harvest! We’ve been harvesting on Monday and Thursday each week since 7/30 or maybe 7/26, I’ve already forgotten! Numbers have leapt up: 10, 34, 37, 99. We need 22 melons a day during hot weather, to keep 100 people happy. So for all of August, September and a few days of October, we need 700-800.

But today’s 99 is not our all-time record. In 2010 we picked 120 on 7/31. And in 2008 we picked 320 on 8/20. That was too many and too late in the year. I’ve only got records back to 2000.

2000 was a bad watermelon year. We used to transplant into hay mulch, for weed control. Of course, we knew hay would cool the soil, and watermelons love heat. But we just couldn’t deal with the weeds any other way. We hadn’t started using drip tape irrigation back then, so our overhead sprinklers watered all the weed seeds in the aisles between the rows too. We used a vast space, with 10′ between the rows. We didn’t get ripe melons till well into August. 2001 wasn’t much better.

In 2002 I did some research into plant spacing and found we didn’t need to give the plants (and weeds) so much space. So we cut the row spacing down to 5.5′ and planted twice as many melons. 5.5′ is just the right width for unrolling big round hay bales between the rows. We started harvesting 8/3. Much better! We got 60/week in the middle of August and 100/week by the end of August. Still peaking much later than sensible. Watermelon in October is like yesterday’s newspapers – there’s not much demand.

2003 had a wet spring, we planted into mud. The harvest peaked 9/16. In 2004 transplanting dragged out. Our new rowcover had a manufacturing defect and disintegrated like wet toilet paper all over the field. We got our money back but the plants were set back by the lack of cover when they needed it. We started saving our own seed that summer, selecting for early ripening and good flavor. Also presumably for spring cold-hardiness as they were from plants that didn’t die.

In 2005 I did more research into spacing, and we planted 2.5′ apart in our 5.5′ rows. It seemed wiser to plant closer and go for more plants and so more first melons (one on each plant), as it is early ones that we want. Keeping geriatric vines alive to produce a third melon or so seemed to be missing the whole point of eating watermelon in hot weather.

At this point in our history, we were still harvesting up until frost (average mid-October here). We were planting about 1260′. We started to track how many melons we had on hand and what rate we were consuming them, so we could decide when we had enough and stop picking.

In 2008 we had no hay mulch available. From this disaster came a wonderful thing: we discovered biodegradable plastic mulch. We have used two brands: Eco-One Oxo-Biodegradable mulch  (made in Canada) and Bio-telo (made in Italy). This product is made from non-GMO corn and it starts to disintegrate after a couple of months in the field. It’s very thin and easily torn if the soil underneath is not smooth. It’s perfect for vining crops, because it stops the weeds growing and doesn’t disintegrate much until after the vines cover the whole area. And the big plus is that the bio-mulch warms the soil, rather than cooling it. Biodegradable mulches are now available in smaller pieces for backyard growers, from Johnnys Selected Seeds and Purple Mountain Organics.

We planted 1800′,  more than usual because the area the rotation brought them to was a bowl shaped garden where crops sometimes drown in wet years. We started harvesting 7/31, and numbers rose rapidly.We didn’t get any floods.  By 8/20 we had harvested 1000. That was the year we decided not to wait for frost, but to disk the patch in early and get a good cover crops established for the winter.

2009 had a peak harvest of 174 on 8/15. I think we stopped at 835 total on 9/2. 2010 records show an early start with 2 harvested on 7/18. We stopped at 665 on 9/8. We tried to experiment with various row spacings and plant spacings, but once the vines all meshed together and the weather got hot, our enthusiasm for science waned! We were planting 1060′. August had an inhuman workload, and we decided to see what we could do to reduce August tasks for future years.

In 2011 we decided to plant less, as were short of workers. We planned on 1080′ but then cut back further, and only planted 900′. This year we only planted 800′, with plants 36″ apart, so a lot fewer plants than in the old days of 1800′ and 30″ spacing. The melons are huge this year – I bet we don’t eat 22 of these a day!

So, having looked at the numbers here in the relatively cool office, I deduce that we haven’t picked anything like enough yet, and need 5 more 99-harvest days before we think about quitting. Time to start using the truck rather than the garden carts, for hauling them away. We’ve found the hard way that even though we can get 20 or so melons in a garden cart, it damages the carts and wrecks the tires. So now we keep to a 16-watermelon limit and save the carts.