Optimization of Pyrolysis Operating Parameters for Biochar Production from Palm Kernel Shell Using Response Surface Methodology

The growing demand for clean and sustainable energy has catalyzed global efforts toward greener economies and sustainable development. In this study, we investigated palm kernel shell (PKS) biomass obtained from a palm oil mill in Omu-Aran, Nigeria (Latitude 8°08ʹ18.85ʺN and Longitude 5°06ʹ9.36ʺE) as a potential feedstock for biochar production. The biomass underwent pretreatment and sieving into particle size ranges of 0.1-0.2 mm, 0.2-0.4 mm, 0.4-0.6 mm, 0.6-0.8 mm, and 0.8-1.0 mm, and was stored in zip-locked polyethylene bags at room temperature for subsequent characterization and pyrolysis experiments. Response surface methodology (RSM) was employed to model and optimize the operating parameters of pyrolysis. The maximum biochar yield (41.1 wt%) was achieved under optimal conditions: temperature of 320°C, reaction time of 6.5 min, heating rate of 12.8°C/min, nitrogen flow rate of 25 cm³/min, and particle size of 0.9 mm. The model exhibited a p-value of 0.05, a high F-value for biochar (340.5), and an R² of 0.9887, signifying its appropriateness, reliability, responsiveness, and accurate prediction of experimental data. A strong correlation between actual and predicted values for biochar yield was observed. Fourier-transform infrared (FT-IR) spectroscopy revealed the presence of alcohol groups, as evidenced by peaks at 3906.3, 3809.3, 3749.7, 3649.7, 3678.9, and 3600.6 cm^-1, as well as alkynes and alkenes, indicated by high-intensity peaks at 2113.4 and 1904.4 cm^-1. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses of the biochar showed white deposits, cleavages, heterogeneous pores, and cloudy formations, indicating inorganic materials and rapid efflorescence during pyrolysis.