Valorization of almond shell biomass to biocarbon materials: Influence of pyrolysis temperature on their physicochemical and electrical conductivity

Authors: DEBEVC, SUSAN - University Of Guelph; WELDEKIDAN, HAFTOM - University Of Guelph; SNOWDON, MICHAEL - University Of Guelph; VIVEKANANDHAN, SINGARAVELU - Virudhunagar Hindu Nadars' Senthikumara Nadar College (VHNSN); Wood, Delilah - De; MISRA, MANJUSRI - University Of Guelph; MOHANTY, AMAR K - University Of Guelph

Submitted to: Carbon Trends
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2022
Publication Date: 9/13/2022
Citation: Debevc, S., Weldekidan, H., Snowdon, M., Vivekanandhan, S., Wood, D.F., Misra, M., Mohanty, A. 2022. Valorization of almond shell biomass to biocarbon materials: Influence of pyrolysis temperature on their physicochemical and electrical conductivity. Carbon Trends. 9. Article 100214. https://doi.org/10.1016/j.cartre.2022.100214.
DOI: https://doi.org/10.1016/j.cartre.2022.100214

Interpretive Summary: Agricultural residues are currently used as animal feed or are incinerated, yet they have the potential to become eco-friendly, value-added products. Biocarbon with a high carbon content increases its value because it becomes more electrically conductive with increased carbon content. Using high heat treatments, we were able to increase the carbon content in almond shells from 47% to 75% in the biocarbon. The high electrical conductivity of almond shell biocarbon produced at high temperatures suggests applications where electrical conductivity is a desirable property such as a composite filler with an electrically conductive matrix or as an activated carbon material.

Technical Abstract: Recent efforts to reduce societal waste has brought up issues with the current linear economic system. Agricultural wastes are presently being used as animal feed or are incinerated, yet they have the potential to become eco-friendly, value-added products. The physical and chemical properties of biocarbons produced from agricultural waste feedstock differ based on pyrolysis conditions, mainly pyrolysis temperature. In this study, almond shell biomass was carbonized at three different temperatures: 300, 500, and 700°C. The resulting carbonized biomasses were analyzed to understand how the physical and chemical characteristics were affected by pyrolysis temperature. The carbon content in almond shells rose from 47% in the biomass to 75% in the 700°C biocarbon. TGA-FTIR spectra indicated that volatiles such as CO2, hydrocarbons, carbonyl groups, and ethers were released at increasingly higher temperatures as carbonization increased, demonstrating the improved thermal stability of almond shells biocarbons. The almond shell biocarbons produced at 500 and 700°C underwent Raman analysis. The deconvoluted peaks ID/IG ratios were 1.274 and 1.012 for 500 and 700°C biocarbons respectively, indicating a trend of increasing graphitic ordering of carbon with increasing pyrolysis temperature. Almond shell biocarbon produced at 700°C was 53 times more electrically conductive than biocarbon produced at 500°C, likely due to the high carbon content and increased graphitic ordering. Further research could be done for application of 500 and 700°C almond shell biocarbons as composite fillers and 700°C biocarbon as an activated carbon material.