Advancements in biochar-reinforced 3D printing filaments for material extrusion: A review on material performance, sustainability, and circular economy

Additive manufacturing has emerged as a promising technology in the manufacturing sector. However, challenges in achieving the desired thermal and mechanical performance often result in reliance on fossil-based fillers. Biochar, a carbon-rich material derived from agricultural waste, has gained attention as an eco-friendly additive. Factors influencing the performance of biochar-reinforced polymer composite from conventional manufacturing were obtained and investigated in biochar-reinforced 3D printing filaments. With a relatively new research area, this review synthesizes recent progress and pioneering studies on applying lignocellulosic biochar for 3D printing filament for material extrusion. The parameters identified include biochar feedstock type, production method, loading level, and compatibilizers. Biochar produced at lower temperatures (<500.0 °C) enhances mechanical strength, while higher temperatures (>700.0 °C) improve thermal resistance. Successful biochar loading for 3D printing filament ranges from 0.1 to 0.6 wt% for fruit by-products biochar and up to 50 wt% for wood-derived biochar, with tensile strength, flexural strength, and modulus improved by up to 60.0 %, 82 % and 175 %, respectively. Biochar also enhances interfacial bonding with a compatibilizer, with successful biochar loading increased from 0.6 wt% to 1.0 wt%. This review also explores the broader role of biochar-reinforced 3D printing filaments in advancing a circular and carbon-neutral economy, addressing the 6 “R”s of sustainability, alongside economic considerations, including cost-effectiveness and market potential. The discussion highlights the commercial viability of biochar as a filler and its potential to support sustainable, low-impact manufacturing, positioning it as a valuable solution in the transition toward greener production systems.