Utilizing pistachio shell biochar to replace carbon black in natural rubber composites

Authors: Peterson, Steven - Steve; Chisholm, Bret

Submitted to: Journal of Composites Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2024
Publication Date: 11/19/2024
Citation: Peterson, S.C., Chisholm, B.J. 2024. Utilizing pistachio shell biochar to replace carbon black in natural rubber composites. Journal of Composites Science. 8, 482. https://doi.org/10.3390/jcs8110482.
DOI: https://doi.org/10.3390/jcs8110482

Interpretive Summary: Carbon black is sourced from fossil fuels and unsustainable, and its production increases greenhouse gas emissions. Biochar is a sustainable, domestic source of carbon from biomass that can partially replace carbon black in rubber composites. In this research, we discovered that biochar made from pistachio shells could replace up to 40% of the carbon black in a rubber composite and increase its strength, elongation, and toughness. Rubber composite products like belts, hoses, seals, and gaskets would benefit from the addition of pistachio shell biochar, and this would also reduce our dependence on fossil fuels and reduce greenhouse gas emissions.

Technical Abstract: Biochar is a sustainable form of carbon made from biomass that potentially can replace carbon black (sourced from fossil fuels) as a filler in rubber composites. Pistachio shells are a prolific agricultural waste product that is a suitable feedstock for biochar. Unlike many other agricultural residues, pistachio shells are a feedstock that yields biochar with high carbon content (>80%) and low ash content (<5%), which is necessary to replace carbon black without detrimental effects to the final composite. Filler blends of pistachio shell biochar and carbon black were explored to see how much carbon black could be replaced before composite properties were affected. Pistachio shell biochar was able to replace up to 40% of the carbon black while improving the tensile strength, elongation, and toughness of the rubber composites, but a reduction in modulus was observed. Based on the results obtained, pistachio shell biochar would be suitable for partially replacing carbon black in applications like hoses, seals, belts, and gloves, thereby enabling a new application for this sustainable, agricultural waste product that will help reduce dependence on fossil fuels.