Recycling of polypropylene by supercritical carbon dioxide for extraction of contaminants from beverage cups. A comparison with polyethylene terephthalate and polylactic acid

Abstract

BACKGROUND: EU policies towards a circular economy address plastic packaging as one of the significant concerns and sets ambitious recycling targets. Polyolefins (POs) cannot be recycled for food contact using conventional polyethylene terephthalate (PET) recycling approaches. Thermal degradation prevents the use of high temperatures and, consequently, decontamination of POs may be insufficient when using lower temperatures. Polypropylene (PP) beverage cups were decontaminated using supercritical fluid extraction with carbon dioxide (scCO 2 ). Decontamination efficiencies (DEs) of selected markers were determined in challenge tests following European Food Safety Authority guidelines. The effects of time (10-60 min) for PET, polylactic acid (PLA), and PP and temperature (60-80 °C) for PP were studied at constant pressure. The physical properties, sensorial properties, and overall migration of treated scCO 2 PP were analysed and compared with virgin PP. RESULTS: PP showed the highest average DE, and PET the lowest, for all the surrogates and in all time conditions. A relative increase in the DE with the increase in process time, particularly for PET and to some extent for PLA, was seen. For PP, no significant impact of time and temperature was observed under the conditions tested. The DE of volatile surrogates was higher than that of semi-volatiles. Results indicate that the scCO 2 treatment did not affect the physical and sensorial properties, nor the overall migration of PP, although it contributes to a considerable reduction in extractable n < C24 alkanes.CONCLUSIONS: Results indicate that scCO 2 can be used to decontaminate post-consumption PP beverage cups with higher DEs than those for PET and PLA, applying mild processing conditions.

Drivers, advances, and significance of measures for effective circular food packaging

“…However, the recycling rates are still relatively low in many countries: in 2020, the EU had an average plastics packaging recycling rate of 39% (Eurostat, 2022) because of the limitations that will be further discussed. Mechanical recycling is the most common approach used for recycling plastics (Singh et al, 2022). This refers to the processing of plastics waste into secondary raw material or products without significantly changing the material's chemical structure.…”

“…The exception applies to polyethylene terephthalate (PET), which has more than 200 established recycling processes for food contact (evaluated by the European Food Safety Authority -EFSA), primarily bottles. In contrast, currently, there is no significant food-grade recycled polyolefins or polystyrene-based materials available for incorporation in new food containers, for example polypropylene (PP), which is used as yogurt, and margarine containers, bottle caps, ketchup bottles, and beverage cups and accounts for ca 20% of the European plastic demand with more than 40% used in packaging (Plastics Europe, 2019;Singh et al, 2022). In Europe, a few processes for no-PET recycling received a positive opinion from EFSA, and some mechanical processes received a letter of non-objection by the US FDA.…”

“…In Europe, a few processes for no-PET recycling received a positive opinion from EFSA, and some mechanical processes received a letter of non-objection by the US FDA. However, they regard either closeloop recovery or limited contact conditions, and they apply to relatively less demanding food contact specifications (Singh et al, 2022). So, most plastic packaging is either recycled into lowerperformance applications or sent to waste-to-energy conversion or landfilling due to a lack of technology at industrial scale to recycle no-PET plastics.…”

“…To create an effective CE, closing all loops to ensure that postconsumer plastic waste is consistently and efficiently turned back into new packages is required (Singh et al, 2022). However, due to some degradation, there is a finite number of cycles that can be performed.…”