Study on Characteristics and Energy Content’s Optimization of Torrefied Oil Palm Empty Fruit Bunch Biochar
Malaysia has enormous biomass resources especially in agricultural field and the most outstanding coming from oil palm plantation. By taking oil palm empty fruit bunch (OPEFB) into consideration, this research was conducted to characterize the torrefied OPEFB biochar from torrefaction process as a potential renewable energy sources based on the influence of parameters particle size, holding temperature and residence time on energy content. By using response surface method (RSM), box-Benhken model has been applied for generating shortest experiment run, and analysis of variance (ANOVA) has been utilized for the optimization. The surface morphology as well as bonding behavior of the torrefied OPEFB biochar have been investigated using scanning electron microscope (SEM) and Fourier transformation infrared spectroscopy (FTIR) respectively. The thermal behavior of torrefied OPEFB biochar has been identified using thermogravimetric analysis (TGA-DSC), meanwhile characterization of ultimate elements has been running by CHNS analyser and crystallinity index (CI) has been conducted using X-ray diffractometer (XRD). From ANOVA, in case to obtain the highest of energy content, the suggested optimized parameters for torrefaction was at 300°C of holding temperature and 90 minutes of residence time, meanwhile particle size did not perform as significant factor for the optimization torrefaction. As the higher holding temperature and longer residence time was applied, the darker color of OPEFB was obtained resulting from carbon content increment. Moreover, both surface morphology and bonding behavior of the torrefied OPEFB biochar was influenced by the degradation of the lignocellulose, hemicellulose, cellulose and lignin. Biochar start to rupture as the longer torrefaction time was applied due to longer period of thermochemical reaction. FTIR spectrum proved that the weak bonds had diminished at this condition. For thermal behavior, the degradation started from the removal of moisture content, proceeded by removal of hemicellulose, cellulose and lignin was decompositions of biochar to completely degrade. From CHNS results, the carbon in raw and torrefied OPEFB biochar was increased while the amount of oxygen is decreasing as holding temperature and residence time increased. This is due to occurrence of decomposition of hemicellulose in this region. For XRD, the decrement of CI is observed as the holding temperature and residence time increased from 200-300°C and 30-90 minutes respectively. This is because the cellulose become completely amorphous as the high temperature and longer time of torrefaction applied.