A viable alternative to plastic?
Since the early 1960s, commercial growers have unrolled countless feet of black plastic film on their fields, and at the end of every growing season looms the job of peeling it back from the soil, packing it up and disposing of it. This end-of-the-season chore costs money, not only in the form of labor, but also in potential disposal fees. In 1991, Oklahoma Cooperative Extension Service’s Dean McCraw and James E. Motes estimated it takes eight hours of labor to remove 1 acre of plastic film. In 2006, Dr. Anu Rangarajan, a horticulturalist and senior extension associate at Cornell University, reported labor and landfill disposal fees associated with black plastic film can cost anywhere from $25 to $100 per acre.
Anyone who uses plastic film factors in the cost of purchasing, laying, removing and disposing of the plastic. Presumably, the benefits reaped outweigh the costs, but what about environmental costs? By 2006, roughly 400,000 acres in the United States were covered with plastic film, and most of that film was carted to the landfill at season’s end. However, plastic is a petroleum-based product, and did you know it takes about 400 years to degrade in a landfill?
There are an increasing number of degradable mulch films on the market, ranging from oiled paper to plastics coated with special chemicals that allow the plastic to break down over time. I’d like to focus here on what I’ll call biofilms. Their main ingredient is corn or wheat starch, and soil bacteria, algae and fungi break those starches down over time, turning them into carbon dioxide and water. If you have healthy soil and suitable growing conditions with respect to temperature, moisture and sunlight, then your soil is capable of degrading biofilms.
Are biofilms as functional as plastic? A number of researchers have set out to answer that question.
In 2006, in Freeville, N.Y., Rangarajan compared muskmelon yields among four Mater-Bi-based biofilms (Mater-Bi black, Mater-Bi brown, Mater-Bi green and BioBag) with black plastic film. Mater-Bi is a material largely derived from cornstarch that is not genetically modified cornstarch, and Novamont, a company based in Italy, developed and manufactures it. At the end of the season, Rangarajan concluded muskmelons grown on biofilms produced yields equivalent to those grown on plastic film. Average melon size and weight were similar across the board. The biofilms did start to break down by the end of July, but overall yields did not seem to be affected.
In 2006 and 2007, Dr. Carol Miles of Washington State University’s Vancouver Research and Extension Unit led a study that compared plastic film to 10 degradable alternatives in 2006 and eight degradable alternatives in 2007. Growth and yields of four organically grown crops (lettuce, peppers, watermelon and broccoli) were monitored. The four biofilm products included in the study were Garden Biofilm, Garden Biofilm NF01U/P 15 mic, Garden Biofilm NF803/P 12 mic and Garden Biofilm NF803/P 15 mic. By early August, two of the biofilms (Garden Biofilm and Garden Biofilm NF803/P 12 mic) had degraded by 50 percent. The remaining two (Garden Biofilm NF01U/P 15 mic and Garden Biofilm NF803/P 15 mic) were considered somewhat durable and associated with high crop yields. All films were tilled into the soil at the end of the season. In the spring, no residues were evident to the naked eye.
In 2007, Dr. Brandon Smith, Dr. Dennis Deyton and Dr. Carl Sams of the University of Tennessee’s department of plant sciences set out to determine whether biofilms are as durable as plastic films when it comes to strawberry production. They compared four of them (.6 mil BioTELO, .8 mil BioTELO, 1 mil Ecofilm and .7 mil BioBag Agrofilm Commercial) to 1.25 mil polyethylene. After the films had been on the ground for 89 days, the .7 mil BioBag product was the only biofilm that did not hold up as well as the plastic film.
It is no surprise that biofilms cost more, sometimes three times more, than regular old black plastic. It is a relatively new industry and demand has not managed to drop those prices quite yet. However, biofilms can be laid using current mulching machines, so no new equipment is required, and because biofilms do not have to be removed at the end of the growing season, you do not have those end-of-the-season labor and disposal costs associated with plastic. Lastly, they are easier on the environment.
At the moment, only noncertified organic growers can use biodegradable films, as these films are not approved for use on certified organic farms in the United States. If you are a noncertified organic farmer and are interested in biofilms, you may want to try one that is approved for organic farms in other countries. BioAgri, a film made from Mater-Bi and manufactured by BioBags (www.biobagusa.com), is approved for use on certified organic farms in the European Union. BioTelo, another Mater-Bi-based film, is approved for use on organic farms by the International Federation of Agriculture Movements, and its biodegradability is certified by Ecocert CAN-USA. BioTelo is manufactured by Novamont and distributed in the United States by Dubois Agrinovation (www.duboisag.com).
Although biofilms are not yet approved for use on certified organic farms in the United States, it is only a matter of time before they are. Yes, they are an off-farm input, and the hackles of many organic purists would go up at the thought of using them, but if they don’t compromise soil health and can decrease our dependency on petroleum-based plastics and reduce the rate at which we’re filling our landfills, then I’m all for them.
The author is a biologist who lives and farms in Vermont’s Northeast Kingdom.