Simultaneous Upcycling of Biodegradable Plastic and Sea Shell Wastes Through Thermocatalytic Monomer Recovery

Abstract

Development of effective upcycling methods for biodegradable plastic waste (for example, straws made of polylactic acid (PLA)) has emerged. In this study, a catalyst derived from sea shell waste (SSC) was used for a thermocatalytic conversion of biodegradable straw (BDS) for the recovery of monomer (for example, lactic acid). In effect, a strategy for simultaneously upcycling of biodegradable plastic waste (for example, straws made of polylactic acid (PLA)) and marine waste (for example, sea shell waste) was proposed. The SSC mainly consisted of calcium carbonate; thus, it had basicity with no acidity. Notably, a temperature of 500 °C and an SSC/BDS mass ratio of 0.5 led to the highest lactic acid recovery from BDS in this study. In particular, the use of SSC under the above-mentioned temperature and SSC/BDS mass ratio resulted in a 130 times higher lactic acid recovery than noncatalytic BDS conversion, most likely because the base sites present on SSC catalyzed the thermal cracking of PLA polymer bond. However, coke deposition was the major deactivation pathway of SSC during the thermocatalytic BDS conversion. In essence, SSC has the potential to be a catalyst used to thermocatalytically recover high-value chemicals from biodegradable plastic waste. In addition, this study can offer insight into developing waste conversion processes for the simultaneous upcycling of biodegradable plastic and marine wastes.