Plastic or glass: a new environmental assessment with a marine litter indicator for the comparison of pasteurized milk bottles

Purpose: Today plastic is the most used material for food packaging, but its incorrect disposal is creating environmental issues to oceans, soil and air. Someone believes that the solution is to ban plastic and substitute it with glass packaging. Is it the right choice? This study aims at comparing the environmental impact of bottles made of PET, R-PET, non-returnable glass and returnable glass in order to understand which is the most environmental friendly packaging solution. Methods: A literature analysis on the environmental impact of glass and PET bottles is carried out, taking into account their production, transport and disposal phase. Then, an environmental assessment of PET, R-PET, glass and returnable glass bottles, used to package 1 l of pasteurized milk, has been carried out using the life cycle assessment methodology and a new indicator. Inventory data were provided by an important milk processing and packaging factory located in Italy. Results were estimated using some relevant impact categories of the ReCiPe 2016 MidPoint (H) method, then a marine litter indicator (MLI) has been proposed in order to evaluate the polluting potential of milk bottles dispersed into the Mediterranean Sea. Results and discussion: LCA results show that R-PET bottle gives the lowest contribution to global warming, stratospheric ozone depletion, terrestrial acidification, fossil resource scarcity, water consumption and human carcinogenic toxicity, followed by PET bottle, returnable glass bottle, and finally non-returnable glass bottle. Glass is the worst packaging option because of high energy demand in the bottle production and its weight and in the transport phase. Some improvements can be obtained with returnable glass, but even if we consider that a bottle could be reused eight times, results are not comparable to the PET or R-PET bottles used only once. However, according to the MLI, returnable glass bottles become the first option, because a lot of plastic bottles could potentially be dispersed into the sea. Conclusions: The substitution of plastic with glass does not help to reduce the GWP and others LCI categories, while could contribute to reduce the marine litter: overall it is important to dispose correctly packaging materials, investing in recycling and reusing. In particular, great improvements can be obtained using bottles made with recycled materials, as R-PET. In conclusion, it is necessary to disadvantage waste dispersion, giving incentives to returnable packaging and raising people awareness of environmental problems.