Biodegradation of aliphatic polyurethane foams in soil with identification of microbial composition and extracellular enzyme activities

Polyurethane (PU) foams are classified as physically non-recyclable thermosets. The current effort of sustainable and eco-friendly production makes it essential to explore methods of better waste management, for instance by modifying the structure of these frequently used polymers to enhance their microbial degradability. The presence of ester links is known to be a crucial prerequisite for the biodegradability of PU foams. However, the impact of other hydrolysable groups (urethane, urea, amide) occurred in PU materials, as well as the supramolecular structure of the PU network and the cellular morphology of PU foams, is still relatively unexplored.In this work, fully aliphatic PU foams with and without hydrolyzable amide linkages were prepared and their aerobic biodegradation using a six-month soil burial test was investigated. Besides the variable chemical composition of the PU foams, the influence of their supramolecular arrangement and cellular morphologies on the extent of biodegradation were also evaluated. Throughout the biodegradation experiment, the release of carbon dioxide, and enzyme activities of proteases, esterases, and ureases were measured. At the same time, PLFA analysis was conducted together with an assessment of microbial biomass of bacteria and fungi achieved by analysing the genetic information from the 16S rRNA gene and ITS2 region sequencing.