Biodegradable Mulch Films: Their Constituents and Suitability for Organic Agriculture

In October 2014, the National Organic Program (NOP) of the US Department of Agriculture (USDA) added biodegradable biobased mulch film to the list of allowed substances for certified organic production. An allowable mulch film, under the new rule, must 1) be biobased as determined by ASTM D6866; 2) biodegrade at least 90% within two years as determined by ASTM D5988 or ISO 17556, and growers must verify that 90% biodegradation is attained in their field(s); 3) meet compostability standards ASTM D6400, ASTM D6868, EN 13432, EN 14995, or ISO 17088; and 4) not be produced using organisms or feedstocks already excluded from organic certification standards (e.g. synthetic, GMO). While minor additives are exempt from the biobased requirement, a 2015 memo by the National Organic Standards Board (NOSB) clarified that 100% of the primary feedstock(s) must be biobased. To date, no biodegradable mulch (BDM) has been certified to meet these requirements. Materials scientists have developed several polymers with the physical and chemical characteristics necessary to create a functional mulch film which also biodegrades under favorable conditions. The foundation of these polymers may fall along a spectrum from completely synthetic (e.g. petroleum-based feedstocks) to completely biobased (e.g. starches). And while most polymers may be completely biodegradable in their pure form, some require additives to ensure timely or complete biodegradation. Additionally, most biodegradable polymers require additives to improve their ability to be processed into film (e.g. plasticizers) or to adequately function as mulch (e.g. colorants). To better understand the challenges growers, and certifiers, face in identifying BDM technologies and products appropriate for USDA-certified organic production, this poster presents BDM products available on the market with information about their feedstocks, manufacturing processes, and biodegradability, as well as some of the most common additives used in BDM manufacture. Additionally, we identify those factors limiting products’ suitability for organic production.