Biochar is derived from the pyrolysis of biomass and contains a large amount of elemental carbon and other inorganic and organic residues [1]. Commonly used as a fertilizer or other type of soil enhancer, biochar has recently attracted some interest as a potential filler for polymers in composite applications, as it is not only created from sustainable resources like crop residue, but also sequesters carbon dioxide making it a low cost and ecologically favourable material [2,3]. Additionally, biochar offers a high thermal stability compared to most other bio-based fillers allowing processing temperatures higher than 220 °C. To assess the potential of biochar as filler for thermoplastic materials and to optimize its processing conditions, composites of polyamide 6 and biochar were produced by injection moulding. It can be expected that the particle size of the filler significantly influences the flow behaviour of the melt and as result particle distribution and therefore the mechanical properties of the composite [2]. Thus, the biochar was prepared by grinding and ball-milling, respectively before addition to the polymer. Those preparation methods yield two different size regimes of biochar particles. It will be shown that decreasing the particle size will change the shear viscosity of the melt and can improve the tensile strength from 70 to more than 80 MPa and the notched Izod impact strength from 19 to 45 J/m. References 1. Wang D, Zhang W, Hao X, Zhou D., Environmental Science & Technology. 2013;47(2):821–828. 2. Peterson S.C., Journal of Elastomers and Plastics. 2013;45(5):487-497 3. Peterson S. C., Journal of Elastomers and Plastics. 2012;44(1):43–54.