Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites

This study explores the valorization of tomato stem waste by converting it into biochar through slow pyrolysis and incorporating it into poly(lactic acid) (PLA) composites for fused filament fabrication (FFF) 3D printing. The objective was to improve the valorization and added value of tomato stem waste. Biochar derived from tomato stems was characterized for its physicochemical properties, revealing a high surface area and small particle size. PLA-based composite filaments with 5% and 7.5% biochar were manufactured via melt extrusion. The effects of biochar concentration and printing infill patterns (concentric and rectilinear) on the mechanical and thermomechanical properties of the 3D-printed composites were investigated. Results indicated that biochar slightly increased the glass transition temperature of PLA and improved the flexural properties. Dynamic mechanical analysis (DMA) showed that the storage modulus was enhanced in the glassy region for composites with 5% biochar, suggesting improved stiffness. This research demonstrates the potential of using tomato stem-derived biochar as a sustainable filler in PLA composites, contributing to the circular economy and reducing environmental impact.