In a recent review published in the journal Biochar, lead author Rachel Day and a team of researchers explored the growing potential of biochar-polymer composites for 3D printing applications. Biochar has long been used for soil health and water filtration, its role as a sustainable filler in the 3D printing industry is gaining traction. The study emphasizes that biochar serves as a renewable and cost-effective alternative to traditional carbon fillers, helping to reduce the carbon footprint of plastic manufacturing while simultaneously improving the physical characteristics of the final products.

The research findings indicate that the amount of biochar added to a polymer matrix is a critical factor in determining the performance of the 3D-printed object. For instance, when small concentrations of biochar were added to recycled plastic, the strength of the material jumped from 40 to 52 megapascals. Other tests showed that adding just one percent of biochar from used coffee grounds into epoxy resin increased its flexural strength by approximately 43 percent. These results suggest that biochar does not just act as a cheap filler but actively interacts with the plastic to create a more robust composite. However, the study also notes that adding too much biochar—generally more than 10 percent—can lead to particle clumping, which actually makes the material weaker and can cause technical issues during the printing process.

One of the primary challenges identified in the review is the tendency for biochar particles to aggregate, which often leads to nozzle clogging in 3D printers. When biochar is added at high levels, such as 30 percent by volume, the material becomes much stiffer and more resistant to wear, but it also becomes significantly harder to print. To solve these issues, researchers have found that post-processing methods like ball milling are highly effective. By grinding the biochar into smaller, more uniform particles, manufacturers can improve the flow of the material through the printer nozzle. Additionally, sieving the biochar to a very fine mesh size has been shown to eliminate clogging entirely at standard printing temperatures, allowing for a smoother and more reliable production cycle.

Beyond the material itself, the study highlights how 3D printing settings can be adjusted to maximize the benefits of biochar. Factors such as the density of the internal structure and the thickness of the printed layers play a major role in how much load the final object can handle. Researchers found that an 80 percent internal density combined with specific layer thicknesses worked best to maximize the strength of certain composites. Furthermore, the angle at which the layers are laid down and the speed of the print head are essential for ensuring that the layers stick together properly. Slower printing speeds were found to improve the bond between layers, resulting in a more durable and consistent final product.

The choice of the original organic material used to make the biochar also significantly impacts the results. Feedstocks with high lignin content, such as woody 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 waste, are particularly well-suited for 3D printing because they produce biochar with a higher surface area and less ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More. This increased surface area allows the plastic to lock into the tiny pores of the biochar, creating a stronger bond between the two materials. Higher temperatures during the biochar production process also tend to increase this porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, though they may result in a lower overall yield of material. By carefully selecting the source material and the production temperature, manufacturers can tailor the biochar to meet the specific needs of different industries, from automotive parts to sustainable packaging.

Source: Day, R., Han, N., Adhikari, S., Wie, J. J., Yoo, C. G., Zhao, X., Webb, E., Ozcan, S., Ragauskas, A., & Pu, Y. (2026). Biochar-polymer composites for 3D printing: a review. Biochar, 8(18).