Biochar from Digestate Pyrolysis as a Filler for Biopolymer Blends: Effect of Blend Composition

Abstract

This study investigates the effect of biochar (BC) as a filler for biopolymer blends, with a focus on the effect of the biopolymer weight ratio on the final BC-added blends. The blends studied in this work were obtained by varying the weight ratio of poly-butylene adipate-co-terephthalate (PBAT) and polylactic acid (PLA) due to their great importance in packaging and agricultural fields. BC has been produced in our laboratories by the slow pyrolysis of the digestate obtained from the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). After pyrolysis, digestate-derived biochar has been milled and sieved to produce a powdery form with diameter of less than 45 μm. In order to better investigate the filler/polymer interactions, biochar particles were dimensionally, morphologically and chemically characterised. The inhomogeneity of the feedstock is responsible for content and high diversity of inorganics in biochar surface. The effect of BC on PBAT and PLA biopolymer matrices is different, and for the blend compositions the relative weight ratio between PBAT and PLA plays an important role. Furthermore, the biocomposite blend has been fully characterised: rheological, morphological, mechanical and dynamic-mechanical characterisations have been carried out, highlighting how the properties results strongly influenced by the presence of BC in the blend. In addition, a study of the viscous molar mass of the two polymer matrices when processed in the presence or absence of BC particless highlighting that a strong chemical interaction occurs between PLA and BC particles, unlike PBAT and BC.