Using atmospheric plasma to design multilayer film from polylactic acid and thermoplastic starch: a screening Life Cycle Assessment

The accumulation of plastic waste and the increasing awareness of the environmental implications and technical challenges associated to their treatment and recycling have led to a constant increase of biopolymers market in the 90's. Polylactic acid (PLA) is one of the most promising biodegradable plastics, showing a wide range of potential applications, e.g. in the packaging industry. However, the high production costs hamper its further development. The use of PLA in multilayer (ML) films is a potential opportunity to reduce the production costs. This study tackled the ecodesign of a clam shell for packaging applications based on a novel ML film made of PLA and thermoplastic starch (TPS), evaluating the environmental performance of different design concepts through Life Cycle Assessment (LCA). In order to assure proper compatibility between PLA and TPS, the use of dielectric barrier discharge (dbd) plasma technology at atmospheric pressure to increase the hydrophilicity of PLA was investigated. The results have highlighted the significant contribution of plasma treatment to the overall environmental impact of the ML film and the need for further optimisation. Despite the contribution of the PLA end-of-life phase to the overall environmental impact of the ML clam shell is low, the methodological approach to end-of-life can have a significant influence on the LCA results. This seems to be due to the low PLA recycling and recovery rate assumed, which is nevertheless realistic. The promotion of high recovery and recycling rates should therefore be a priority in the future. At the current development stage, even the most improved ML clam shell concept obtained using atmospheric plasma technology is not an environmentally sound alternative to pure PLA clam shell, although it is likely to be a cost-effective option. A good compromise between cost and environmental constrains to be further investigated could be to increase further the proportion of PLA in the ML, by improving the water adsorption capability of TPS through, e.g., the addition of a phthalate free plasticiser.