Bio-Char Characterization Produced from Walnut Shell Biomass through Slow Pyrolysis: Sustainable for Soil Amendment and an Alternate Bio-Fuel

Rami Alfattani, Mudasir Akbar Shah, Md Irfanul Haque Siddiqui, Masood Ashraf Ali and Ibrahim A. Alnaser
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Rami Alfattani: Department of Mechanical Engineering, Umm Al-Qura University, P.O. Box 715, Makkah 24224, Saudi Arabia
Mudasir Akbar Shah: Department of Chemical Engineering, Kombolcha Institute of Technology, Wollo University, Kombolcha 1145, Ethiopia
Md Irfanul Haque Siddiqui: Department of Mechanical Engineering, King Saud University, Riyadh 11421, Saudi Arabia
Masood Ashraf Ali: Department of Industrial Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj 16273, Saudi Arabia
Ibrahim A. Alnaser: Department of Mechanical Engineering, King Saud University, Riyadh 11421, Saudi Arabia

Energies, 2021, vol. 15, issue 1, 1-20

Abstract: Bio-char has the ability to isolate carbon in soils and concurrently improve plant growth and soil quality, high energy density and also it can be used as an adsorbent for water treatment. In the current work, the characteristics of four different types of bio-chars, obtained from slow pyrolysis at 375 °C, produced from hard-, medium-, thin- and paper-shelled walnut residues have been studied. Bio-char properties such as proximate, ultimate analysis, heating values, surface area, pH values, thermal degradation behavior, morphological and crystalline nature and functional characterization using FTIR were determined. The pyrolytic behavior of bio-char is studied using thermogravimetric analysis (TGA) in an oxidizing atmosphere. SEM analysis confirmed morphological change and showed heterogeneous and rough texture structure. Crystalline nature of the bio-chars is established by X-ray powder diffraction (XRD) analysis. The maximum higher heating values (HHV), high fixed carbon content and surface area obtained for walnut shells (WS) samples are found as ~ 18.4 MJ kg −1 , >80% and 58 m 2 /g, respectively. Improvement in HHV and decrease of O/C and H/C ratios lead the bio-char samples to fall into the category of coal and confirmed their hydrophobic, carbonized and aromatized nature. From the Fourier transform infra-red spectroscopy (FTIR), it is observed that there is alteration in functional groups with increase in temperature, and illustrated higher aromaticity. This showed that bio-chars have high potential to be used as solid fuel either for direct combustion or for thermal conversion processes in boilers, kilns and furnace. Further, from surface area and pH analysis of bio-chars, it is found that WS bio-chars have similar characteristics of adsorbents used for water purifications, retention of essential elements in soil and carbon sequestration.

Keywords: walnut shells; pyrolysis; higher heating values; bio-char; surface area (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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