Renewable carbon filler Biochar composites for sustainable 3D printing

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Biochar could become a key lever for greener additive manufacturing: A new review shows how small amounts of carbon-rich biomass filler can partially replace petroleum-based polymers while enhancing mechanical, thermal, and even functional properties in 3D-printed parts.

A new review of emerging research suggests that biochar, a carbon-rich material produced from biomass, could play an important role in making 3D printing more sustainable while improving material performance. The study brings together recent advances in biochar–polymer composites and outlines the scientific and engineering challenges that must be solved before the technology can be widely adopted.

Biochar is produced when plant material or organic waste is heated in low-oxygen conditions, creating a porous and stable carbon material. While biochar has long been studied for environmental applications such as soil improvement and pollutant removal, scientists are increasingly exploring its use as a filler in plastics used for additive manufacturing.

Being able to partially substitute petroleum-based poylmers with renewable materials, could make it possible to think about additive manufacturing not only as a design tool but also as a pathway toward more sustainable materials.

The review examines how adding small amounts of biochar to polymers can enhance certain mechanical and thermal properties. In some cases, low concentrations improved strength or stiffness by helping the polymer matrix interact with the porous biochar surface. Because biochar is lightweight and relatively inexpensive, it may also help reduce material costs and overall environmental impact.

However, the authors note that the benefits depend strongly on how the biochar is produced and processed. Feedstock type, pyrolysis temperature, and post-treatment methods all influence particle size, surface area, and chemical composition. These factors determine how well the biochar mixes with polymers and how it behaves during printing.

One of the main challenges highlighted in the review is printability. Unlike polymers, biochar does not melt, which means particles can aggregate or block printer nozzles if their size and dispersion are not carefully controlled. Poor bonding between printed layers can also weaken final parts.

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“Achieving reliable printing performance requires balancing biochar content with particle size, dispersion, and printing parameters,” the authors explained. “There is no single recipe yet, which is why systematic studies linking biochar properties to printing behavior are urgently needed.”

The review also points to promising strategies to overcome these limitations. Physical treatments such as ball milling can reduce particle size and improve dispersion, while chemical modifications can tailor surface chemistry. Adjustments to printing parameters such as infill density, temperature, and raster orientation can further improve final material performance.

Beyond mechanical properties, biochar composites may enable additional functions. Some studies have shown improved electrical conductivity, reduced gas permeability, or enhanced pollutant adsorption in printed materials. These multifunctional characteristics could open new applications in packaging, electronics, environmental monitoring, and construction.

The authors emphasize that research on 3D-printed biochar composites remains at an early stage, but the rapid growth of interest suggests significant potential.

“Our goal was to map out what is known and identify where the biggest knowledge gaps remain,” the authors said. “If we can better connect biochar production methods with printing outcomes, we may be able to design truly sustainable materials tailored for additive manufacturing.”

As industries search for lower-carbon manufacturing approaches, the integration of renewable carbon materials like biochar into 3D printing could represent a promising step toward greener production technologies.

Journal Reference: Day, R., Han, N., Adhikari, S. et al. Biochar–polymer composites for 3D printing: a review. Biochar 8, 18 (2026). https://doi.org/10.1007/s42773-025-00520-9

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