Current Status of Biodegradable Plastic Mulches in Certified Organic Production

There are currently no biodegradable plastic mulch (BDM) products allowed for use in U.S. certified organic production. Petroleum-derived polymers included in BDM formulations render these mulch products unacceptable for certification. To be acceptable, BDMs must be 100% derived from biologically-based polymers like polylactic acid (PLA) and/or polyhydroxyalkanoates (PHA). Although PLA is a biologically based polymer, it may be considered a synthetic since only the monomer is derived from renewable resources and is chemically polymerized. In PHA, microorganisms produce the polymer itself, not the monomer. Mulches must also undergo mineralization within a reasonable time period, and the ultimate fate of degraded polymers must be acceptable to the National Organic Program (NOP) standards. The E.U. and Canada organic standards allow the use of BDMs that contain an additive prohibited in the U.S. With the recent equivalence arrangement of organic standards for export between the U.S., Canada and the E.U., there is a question if these BDMs will eventually be allowed in organic production in the U.S.  Additionally, the Biodegradable Products Institute has recently petitioned the National Organic Standards Board (NOSB) requesting the addition of BDMs currently allowed in Canada and the E.U. under section § 205.206 (c) "Biodegradable Plastic Mulch Made from Bioplastics: without removal at the end of the growing or harvest season.” In an ongoing USDA Specialty Crop Research Initiative (SCRI) study in Washington State, Texas, and Tennessee, researchers are evaluating tomato production with plastic mulch and commercial mulch products advertised as "biodegradable." The study is testing the ability of existing and emerging BDM products to completely biodegrade in the soil environment. To better understand the impact of BDMs on soil systems, more studies are needed to test for the presence or absence of residues and/or toxic intermediates and co-products as well as physical and temporal impacts on soil ecology and plant health. Long-term studies on the impacts of biodegradation of BDM products will help promote new information, product development, and may help producers conform to NOP standards. Insight into the current NOP standards prohibiting the use of BDM, the E.U. standards permitting it, and the most up to date results from the USDA SCRI study on the biodegradability and impact BDMs have on soil quality will be discussed.