Biodegradable plastic mulches (BDMs) are a promising alternative to polyethylene mulch. The concept is simple. Rather than pulling used plastic mulch from a field and stockpiling or disposing it in a landfill, BDMs are designed to be tilled in at the end of the production cycle. Afterwards, soil microorganisms convert BDM fragments into microbial biomass and CO2. Previous research has shown BDM performance in strawberry systems is comparable to PE mulch. Given this, BDMs seem like a sustainable alternative to the current status quo of plastic mulch waste generation and disposal and would be appealing for organic production. However, caution is warranted when considering BDM use in organic systems!

While the USDA National Organic Program (NOP) added biobased BDMs to their list of allowed synthetic substances in 2018, it is important to remember that no commercially available BDMs (with the exception of paper-based films) meet the NOP's criteria for use in certified organic production [7 Code of Federal Regulations, Section 205.601 (USDA 2014)].

To be allowed in organic production, BDMs must:

1. Fulfill criteria for being biobased as evaluated using standardized tests such as ASTM D6866.
2. Be produced without organisms or feedstock derived from excluded methods (e.g., GMOs) [7 CFR, Section 205.601(b)(2)(iii)].
3. Meet compostability specifications of either ASTM D6400, ASTM D6868, European Standards (EN) 13432, EN 14995, or ISO 17088 (7 CFR, Section 205.2).
4. Reach at least 90% biodegradation in the soil within two years or less as evaluated using standardized tests such as ISO 17556 or ASTM D5988.

Completely biobased BDMs that are produced without GMOs is difficult and cost-prohibitive at the manufacturing level. Furthermore, biobased content is not correlated with in-soil biodegradability. Research on the application of BDMs in specialty crop systems is certainly warranted and underway. Part of that research will inform questions pertaining to the application of BDMs in organic systems.

If you would like to learn more about BDMs and issues pertaining to organic production, please visit: https://smallfruits.wsu.edu/plastic-mulches/. You can also participate in National Organic Standards Board meetings and vocalize your questions and concerns regarding BDM use in organic systems.