Characterization of bio-oil and biochar from slow pyrolysis of oil palm plantation and palm oil mill wastes

Wastes from oil palm plantations and mill processing are renewable resources for bio-energy and biochemicals development. The five most abundant oil palm wastes are empty fruit bunch (EFB), palm kernel shell (PKS), palm mesocarp fiber (PMF), palm frond (PF), and palm trunk (PT). These different types of biomass have different properties which can significantly influence the bio-oil products and pyrolysis performance. Bio-oil and biochar were produced by slow pyrolysis of these wastes in a fixed-bed reactor at 600 °C for 60 min. The biomass and pyrolysis products were comparatively characterized using thermogravimetric analysis (TGA), elemental analysis, Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC–MS), and scanning electron microscopy (SEM). The highest yield (25.5 wt%) of bio-oil was obtained from PF, while the highest yield (29.7 wt%) of biochar was obtained from PMF. Fatty acids were the main compounds in bio-oil obtained from EFB and PMF, while those from PKS, PF, and PT contained more aromatics and their boiling point distributions were lower than EFB and PMF bio-oils. Biochar from all the materials decomposed in two stages and showed similar compositions. The variations in the yields and properties of products resulted from differences in the properties of feedstocks. The results could contribute useful data for selection and controlling the pyrolysis of oil palm wastes.