**2.2 δ13C as a possible tool to distinguish petroleum-derived plastics from plant-derived plastics**

 To reduce the impact of plastic debris in the environment, recyclable and more biodegradable polymers (i.e., plant-derived polymers) have been introduced increasingly into the market [10]. Plant-derived plastic polymers used for food packaging, such as bags and bottles for drinking water, showed a significant difference in isotopic values with respect to the petroleum-derived plastic products. In fact, petroleum-derived packaging materials for food use, such as shopping bags for fruits and vegetables (HD PE) and plastic bottles for drinking water (PET), were characterized by the δ 13C mean values of −33.97 ± 1.15 and − 27.84 ± 1.71‰, respectively, whereas plant-derived supermarket envelopes ("BIO" bags) and bottles (PLA, a biodegradable polyester derived from the fermentation of starch and condensation of lactic acid) recorded the δ13C mean values of −25.30 ± 0.70 and −13.87 ± 2.18‰, respectively. As regards to the results obtained for "BIO" bags, values reflected those of C3 plants, while for PLA, the analyses highlighted δ13C values similar to those of C4 plants, suggesting their specific origin.

 This difference suggests that stable isotope analysis could be a useful method to discriminate between petroleum-and plant-derived plastic debris [21, 27]. The most used biopolymers are in fact produced starting from C3 (rice, potatoes, cotton, and cellulose) and C4 (corn and sugarcane) plants, species which differ for photosynthetic pathways and, consequently, for the carbon fingerprint. C3 plants recorded more negative δ13C values (ranging from −30 to −25‰) than C4 plants (ranging from −13 to −11‰), in agreement with Suzuki et al. and authors therein [21]. Considering the isotopic signature of the "BIO" bags, a common and widespread biodegradable product used for many commercial purposes, δ13C values are generally comparable with those reported for C3 plants. Regarding "recycled" polymers, LD PE recycled envelopes showed a δ13C mean value of −27.75‰. The presence of a low quantity of other polymers as impurities or different recycle processes could explain the less negative average value with respect to the row LD PE (−30.19‰) given by an 13C enrichment or depletion (fractionation).

*Elemental Analyzer/Isotope Ratio Mass Spectrometry (EA/IRMS) as a Tool to Characterize... DOI: http://dx.doi.org/10.5772/intechopen.81485* 
