A comprehensive review of biochar-reinforced 3D printing filaments in Composites Part C: Open Access by Diana Rose R. Coronado, Wei-Hsin Chen, and Aristotle T. Ubando, synthesizes recent advancements in this material to push forward the adoption of sustainable manufacturing. The global market for additive manufacturing is growing, driving demand for materials that are not only high-performing but also low-cost and environmentally friendly. Biochar offers a promising solution to replace costly, fossil-based fillers typically used to enhance the performance of 3D printing polymers.

The researchers found that the performance of biochar-reinforced polymer composites is significantly influenced by the biochar’s production temperature, its source (feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More type), the amount added (loading level), and the use of compatibilizers. For example, biochar produced at lower temperatures, specifically below 500.0∘C, has been shown to increase the composite’s mechanical strength. Conversely, production temperatures exceeding 700.0∘C typically result in improved thermal resistance. This difference is attributed to the presence of more oxygen-containing functional groups in lower-temperature biochar, which promotes better adhesion and interaction with the polymer matrix. At higher temperatures, deoxygenation occurs, which reduces the number of these surface functional groups, leading to weaker adhesion.

When applied to 3D printing using material extrusion (MEX), biochar has successfully been incorporated into various thermoplastic polymers, including polylactic acid (PLA), high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), and polypropylene (PP). This material innovation has demonstrated significant improvements in mechanical properties. Specifically, biochar-reinforced filaments have shown enhancements in tensile strength, flexural strength, and modulus by up to 60.0%, 82%, and 175%, respectively. The optimum loading of biochar varies based on the feedstock type. Biochar from fruit by-products typically shows maximum performance at very low loadings, ranging from 0.1 to 0.6 weight percent. For wood-derived biochar, successful loadings can be much higher, extending up to 50 weight percent, especially when techniques like in situ polymerization are used. However, too much biochar can lead to agglomeration and the formation of voids or microcracks, which ultimately reduce the composite’s mechanical performance.

Beyond performance, the use of biochar-reinforced filaments strongly supports the transition to a circular bioeconomy and carbon-neutral manufacturing. Biochar acts as a carbon-negative filler by sequestering carbon absorbed by the biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More during cultivation. This is a significant improvement over fossil-based carbon fillers, the production of which emits millions of metric tons of carbon dioxide annually. Life cycle assessment studies show that incorporating biochar into 3D printing filaments can substantially reduce the carbon footprint, achieving carbon neutrality, for example, with 40% biochar loading in recycled HDPE. Furthermore, by repurposing agricultural and plastic waste into high-value materials, this approach helps to reduce waste accumulation and landfill usage, aligning with the six “R”s of sustainability: reduce, refuse, recycle, rethink, repurpose, and remanufacture. This shift not only presents environmental benefits but also economic advantages, as biochar, derived from low-cost waste streams, is a cheaper alternative to conventional carbon fillers. The enhanced properties of the resulting filaments also extend product lifecycles, further supporting long-term economic viability and driving demand in industries like automotive, aerospace, and construction.

Source: Coronado, D. R., Chen, W.-H., & Ubando, A. T. (2025). Advancements in biochar-reinforced 3D printing filaments for material extrusion: A review on material performance, sustainability, and circular economy. Composites Part C: Open Access.