Thermophilic Composting as a Means to Evaluate the Biodegradability of Polymers Used in Cosmetic Formulations

Abstract

In the last decade, a growing demand for sustainable cosmetic ingredients has yielded numerous biodegradation protocols. While OECD (Organization for Economic Co-operation and Development) aquatic assays are suitable for water-borne chemicals, it is crucial for the personal care industry to consider the persistence of plastics in soil, compost, and municipal sludge. Adopting this cradle-to-grave holistic approach would strengthen product appeal while increasing the accuracy and ethical integrity of green product labeling. The aim of our study was to employ quantitative CO2 detection and thermophilic composting protocols specified in ASTM D5338, along with pass level criteria outlined in ASTM D6400, to assess the mineralization of plastics commonly formulated into personal care products. Our results indicate that many cellulose ethers, cationic guars, starches, proteins, and labile polyesters demonstrate satisfactory disintegration, biodegradation, and seed germination rates to secure an ASTM D6400 compostability claim. By contrast, macromolecules designed with carbon–carbon backbones resisted acceptable mineralization in composting experiments, advocating that unadulterated municipal compost lacks the microbial diversity to enzymatically digest many synthetically derived resins. Additionally, polymers that demonstrated acceptable biodegradability in internal and published OECD aquatic studies, including chitosan and polyvinyl alcohol, exhibited limited respiration in local municipal compost; hence, untested correlations between aquatic, soil, and compost testing outcomes should never be assumed.

Keywords

• biodegradation
• ASTM D5338
• ASTM D6400
• polysaccharides
• sustainability
• respirometry