Unprecedented high percentage of food waste powder filler in poly lactic acid green composites: synthesis, characterization, and volatile profile

The attractive qualities of plastics lead us, around the world, to an enormous need for plastic goods, which results in their unsustainable overconsumption. Bio-based products are the core concept of circular economy, yet this sector suffers from the high cost of their production. In practice, biopolymers, such as polylactic acid (PLA), are still limitedly used, due to their expensiveness and not outstanding technological properties. A circular and sustainable solution would be to use waste from the food industry as filler that contributes to reduce the cost of PLA-based materials, thereby encouraging their widespread use. At the same time, this would be a circular approach to wisely upgrade food waste and prevent pollution. Ceramic food waste powder fillers from egg shells and from mussel shells were compounded with PLA at 180 °C to obtain composites, which contain an unprecedented high amount of filler, equal to 140 over 100 parts of PLA. We analyzed volatile organic compounds emitted from PLA and, for the very first time, from its composites via headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The molecular fingerprint of the volatiles comprises only three aldehydes, a ketone, and two lactides. Volatiles typical of fossil plastics, that are causative factors of hormone disruption or reproductive dysfunction, are effectively missing. Scanning electron microscopy, used to examine the structure of the composite, indicates that both the egg shells and the mussel shells are suitable fillers, in that they form a sufficiently strong interface with the polymer.