Optimization of Biochar Production from Slow Pyrolysis of Oil Palm Waste

Abstract

The Malaysian palm oil industry has grown rapidly in recent years. An abundance of oil palm biomass is generated from the palm oil mil, including fronds, trunks, mesocarp fibre, shells, and empty fruit bunches (EFB). These oil palm wastes (OPW) were potentially converted into value-added products such as syngas, bio-oil, and biochar through thermochemical conversion technology. In this study, the optimization of OPW-derived biochar was conducted using the Box-Behnken design (BBD) and response surface methodology (RSM). The effects of pyrolysis temperature (400-700 °C), pyrolysis time (30-120 min), and nitrogen flow rate (0.4-1.0 L/min) on biochar yield were analysed. The results demonstrated the highest biochar yield (27.2 wt%) was obtained from pyrolysis of EFB at 550 °C for 75 min under 0.7 L/min N2 flow. Then, other OPW sample namely oil palm trunk (OPT), oil palm frond (OPF), and palm kernel shell (PKS) were pyrolyzed at the optimum operating condition. The produced biochar was characterized with thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The results show the highest yield and thermal stability of biochar produced from pyrolysis of PKS compared to other OPW samples. The surface features of PKS-derived biochar also displayed well-developed pores and a honeycomb-like shape. Hence, PKS can be optimized to obtain high-quality biochar.