## 4 Conclusions  
Coconut shell biochar-incorporated PLA/PBAT polymer composites show improvements in mechanical and electrical properties (surface resistivity \(\sim\)10\({}^{11}\)\(\Omega\)/sq) and are suitable for antistatic application (antistatic material). Antistatic property can be achieved for the composite with a low biochar-loading concentration (10 wt%) instead of the previously reported 30 wt% of wood-biochar addition for antistatic PLA/PBAT composites. The XRD and XPS studies on coconut shell biochar reveal that it contains high carbon content with sp\({}^{2}\) hybridised graphitic carbon, improving the conductivity of the filler particles. The presence of highly pure carbon without impurities, a low percentage of functional groups, and reduced particle-size are beneficial for improving the electrical properties of the composites. TGA and DSC analyses show that the biochar composites are thermally stable, and the biochar particles act as nucleating agents, promoting PLA crystallisation. The tensile strength of the 3D-printed specimens with 1 wt% of biochar, PLA/PBAT/BC (79/20/1), shows the highest average value of 42.3 MPa. However, the tensile modulus and elongation at yield remain steady without appreciable change. The interfacial interaction of the biochar and polymer matrix studied using SEM reveals that the biochar has a strong interaction with the polymer matrix, possibly due to the low concentration of functional groups associated with the biochar particles. Here, biochar improves the compatibility of the PLA and PBAT phases, improving the composite's mechanical properties, especially the tensile strength. Furthermore, the electrical resistivity of the composites decreases with the addition of biochar, and the composite with 10 wt% of biochar shows a surface resistivity of \(\sim\)10\({}^{11}\)\(\Omega\)/sq, without any significant reduction in mechanical properties, making it a suitable antistatic material for packaging applications or personal protective equipment (PPE). Hence, the coconut shell biochar-filled PLA/PBAT composite is a suitable sustainable, environment-friendly, low-cost material for antistatic applications. Further studies on the improvement of the electrical properties of the biochar filler (with optimised pyrolysis conditions) and the effects of nano-sized biochar particles on the electrical and mechanical properties, are being conducted.  
J.G.: conceptualization, methodology, formal analysis, writing--original draft preparation. writing--review and editing. D.J.: writing--review and editing. D.B.: resources, supervision, funding acquisition, validation, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
Ministry of Business, Innovation & Employment, New Zealand, for their financial support (grant number: UOA 3706657).  
Not applicable.  
Figure 10: (**a**) tensile strength, (**b**) tensile modulus and elongation at yield of the composites.  
**Acknowledgments:** The authors thank all technicians at the Centre for Advanced Composites Materials (CACM) for their assistance. In addition, the authors would like to acknowledge the Ministry of Business, Innovation & Employment, New Zealand, for their financial support (grant number: UOA 3706657).  
**Conflicts of Interest:** The authors declare no conflict of interest.