Recycling of biopolymers - The patent perspective

The present study investigates the main recycling technologies of biopolymers, including bio-based and/or biodegradable polymers, disclosed in the patent literature. Most of the retrieved patents relate to the recycling of aliphatic polyesters, in particular PLA, which is nowadays the most commonly used biodegradable polymer. The main recycling technologies, which are examined, are sorting, mechanical recycling, chemical recycling (hydrolysis, alcoholysis, and thermal depolymerization with catalysts) and the relatively new enzymatic depolymerization of biopolymers. Currently, mechanical processing of post-industrial waste appears to be the only realistic option for the recycling of biodegradable PLA. Bio-based non-biodegradable polymers, such as bio-PET, bio-PE, bio-PA can be mixed with their fossil fuel-based counterparts and recycled in existing recycling facilities. Poly(ethylene furanoate) (PEF) can also be mixed with industrial PET in an amount up to 2%, and recycled. Despite the dynamic growth of biopolymers their waste streams are still small and scattered; and no separate recycling stream yet exists for PLA. On the other hand, there is much activity in patenting on the recycling of biopolymers. Most of the information presented in this paper is not to be found anywhere else, but in patents.