3D Printing of Starch, PLA & Lignin

3D printing significantly advances the principles of bioeconomy and circular economy through waste minimization, promotion of resource efficiency, and sustainable design. To aid the transition from a petroleum-based to a bio-based economy, we propose to create a fully bio-based and biodegradable polymer for 3D printing by valorizing renewable biomaterials – starch and lignin. These materials have a lower carbon footprint compared to petroleum-based chemicals used for 3D printer filaments, e.g., Acrylonitrile Butadiene Styrene. To make the filament, lignin was extracted with a yield of 32.7% from waste barley straw from the food industry using an ethanol-organosolv process. The extracted lignin was characterized using FTIR, Klason Lignin and 2D HSQC NMR. The different batches of extracted lignin were found to be homogeneous, had an average purity percentage of 86.4% lignin, and the prominent linkages between monolignols were β-O-4 and β-α-O with cinnamyl alcohol ending groups. Modified starch, PLA, and binder were mixed with lignin at different proportions. The biocomposite mixtures were extruded and the extruded filaments were analyzed using DSC. Similarly, Polarized Optical Microscopy (POM) and Scanning Electron Microscopy (SEM) were used to analyse the distribution of these biocomposite in the filament. The result suggested that the biocomposites distributed unevenly but each of the components were able to bind to each other suggesting a uniform mix. Tensile Strength, was successfully carried out. Results were influenced by testing conditions and sample preparation. As the amount of PLA% was increasing the more strength the sample has. While at the same time those sample showed low ductibility and high elasticity. To assess the environmental impacts of the filament production, a cradle-to-grave LCA was carried out. Carbon footprint (2,4 kg CO2eq/kg biocomposite) shows similar impacts compared to other biobased and petrobased biocomposites, but higher water footprint (54L/kg) and land use impacts (1,9m2crop.eq/kg) compared to petrobased biocomposites. Regarding carbon footprint, raw materials are the most impactful stage, with 48% of total impacts, then processing steps (energy) with 44%, and finally end-of-life management and delivery (8%). Sensitivity analysises emphasizes the weight of national electricity grids.