Ex-ante life cycle assessment of polymer nanocomposites using organo-modified layered double hydroxides for potential application in agricultural films

Abstract

Biodegradable agricultural films made of poly(butylene adipate-co-terephthalate) (PBAT) are interesting alternatives to the most commonly used low-density polyethylene (LDPE) films. Photodegradation of both types of polymers can be prevented by the addition of UV stabilizers. To prevent leaching of the additives from the films, the stabilizers can be intercalated in layered double hydroxides (LDH). When LDHs are exfoliated in the polymer a nanocomposite is formed with improved material properties. An ex-ante cradle-to-grave life cycle assessment (LCA) is conducted on the application of nanoclays in agricultural mulching films. The PBAT/LDH nanocomposite is compared with PBAT and LDPE, both of which had been UV-stabilized with the conventionally used compound Irganox 1010. Being key ingredients of the nanocomposites we prepare an ex-ante cradle-to-factory gate LCA for different nanoclay compositions containing surfactants and the non-toxic UV stabilizer p-hydroxycinnamic acid intercalated in LDH sheets. Among the nanoclays, the lowest environmental impact is achieved by LDHs based on magnesium oxide/hydroxide and aluminum oxide/hydroxide, with the surfactant stearate as the intercalated anion. Our comparative analysis of mulching films shows that the lowest non-renewable energy use and greenhouse gas emissions are obtained by LDPE films, which are recycled and incinerated with energy recovery after the second life cycle. However, recycling and energy recovery are not always applied, which makes the biodegradable PBAT an interesting alternative. Further study on the UV stability, tensile strength and bio-based feedstock for PBAT indicates that PBAT containing LDH and p-hydroxycinnamic acid can be an environmentally friendly alternative to LDPE agricultural films containing the UV stabilizer Irganox 1010.