Thermochemical Conversion of Cashew Nutshell Through Slow Pyrolysis: Process Optimization and Product Yield Analysis using Response Surface Methodology
1*Oniya, O. O., 2Nasirudeen, A. R., 1Ola, F. A., 1Oyekunle, Y. Y. and 3Omoyeni, O. D.
1Department of Agricultural Engineering, Ladoke Akintola University Technology, Ogbomoso, Oyo State, Nigeria.
2Department of Agricultural and Bio-Environmental Engineering, Oyo State College of Agriculture and Technology, Igboora, Nigeria.
3Department of Agricultural and Bio-Resources Engineering, Federal University Oye Ekiti, Ekiti State, Nigeria.
DOI: 10.36108/laujoces/6202.71.0152
Abstract
This study investigated the slow pyrolysis of cashew nutshell (CNS) to evaluate the effects of heating temperature (300–700 °C) and holding time (20–100 min) on product yields (biochar, bio-oil, and syngas). Using a Central Composite Design through Response Surface Methodology (RSM), experiments were conducted on cleaned and sun-dried CNS sourced from Oyo State, Nigeria. Experimental data were statistically analyzed using Analysis of Variance (ANOVA) at a 95 % confidence level. Under the experimentally tested pyrolysis conditions, yields ranged from 42–72 % for biochar, 6–29 % for bio-oil, and 22–36 % for syngas. The quadratic models for biochar and syngas were statistically significant (P≤0.05) with R² values of 0.9487 and 0.9474, respectively. The bio-oil model exhibited a lower fit (R² = 0.49), indicating that liquid yield is influenced by factors beyond the tested variables. These findings establish a reliable framework for understanding the thermochemical valorization of cashew nutshell residues, highlighting heating temperature as the dominant factor governing product distribution.
Keywords: Lignocellulosic biomass, Response Surface Methodology, slow pyrolysis, optimization biochar yield, bio-oil, syngas, heating temperature, holding time.