Kelvin Okamoto, Ph.D.

Perfluoroalkyl substances (PFAS) is a broad class of chemicals of which many have been found to have adverse human health effects and/or to be environmentally persistent. Common materials such as Teflon™ polymers and coatings, Gore-Tex fabric and Scotchgard stain resistant chemicals are PFAS. In packaging, PFAS have many uses including in pulp molded products to impart water and grease resistance and as lining for microwave popcorn bags. Unfortunately, PFAS in packaging that is composted stays in the finished compost and then is transferred to the environment when the compost is spread on gardens, etc. and then washes into open waters with rain, irrigation or other means.

Thus, many localities such as San Francisco have banned the presence of PFAS in items to be composted. The Compost Manufacturing Alliance and all other industrial compostability certification agencies have similarly banned the use of PFAS in certified products and materials for industrial compostability since January 1, 2020 and before. Ideally, the presence of PFAS can be determined by chromatographic means for identifying the specific PFAS in the product or material; this requires the extraction of the PFAS intact from the product or material. However, three issues prevent this, the first is that PFAS binds to natural fibres and thus will not extract, the second is that not all specific PFAS chemicals have been identified for identification by chromatography and the third is expense.

Thus, a simpler means to detect the presence of PFAS is to measure the amount of fluorine (F) in the product or material, i.e. total fluorine analysis. To perform this analysis, the material must be digested, i.e. broken down, and then use well-known methods for determining F amount. The one complicating factor known early is that several non-PFAS chemicals also contain F; this includes common fillers and minerals such as talc. Thus, the non-PFAS chemicals containing F must also be tested independently and their contribution to the total F content of a material must be subtracted from any test result.

A second issue was raised by pulp molded foodservice ware manufacturer. In testing at outside labs, total F content reported varied from nearly non-detectable to over 1000 parts per million (ppm), i.e. from acceptable to not acceptable F content. The manufacturer stated that they did use PFAS in the product and thus the total F content should be over 1000 ppm. After talking with Ron Walling of Advanced Materials Center (AMC), AMC started a project to determine what the issue was. Working with three labs that test for fluorine, side-by-side analysis of products with and without PFAS. The study determined that the issue is the difference in the digestion methods used prior to the F content analysis. Some labs used an open crucible and others used a Paar bomb or closed crucible for the heated digestion. As F is volatile, the open crucible released the F to the atmosphere and thus gave a low F content after analysis. Thus, total F analysis requires that sample digestion be performed by a Paar bomb. CMA allows total F analysis by only approved labs after the proper digestion method.