Investigation of high water content in bio-crude oil (BCO) produced from empty oil palm fruit bunches pyrolysis

The abundance of empty oil palm fruit bunches (EFB) makes it attractive to be processed through pyrolysis. Despite many studies dealing with it, the investigation of high water content in bio-crude oil (BCO) is often overlooked. Hence, this study intends to disclose it along with the analysis using water balance. EFB was pyrolyzed to produce BCO at 400 °C, 500 °C, and 600 °C in the reactor with diameters of 3 in., 4 in., and 5 in. Results show that heat distribution is more stable at the bottom of the fuel chamber. The larger reactor diameter also impacts poorer temperature distribution since the heat propagation resistance becomes more significant. The highest BCO yield (35.93%) is achieved at 400 °C in a 3-in. reactor. The water content of this BCO is 59.30–84.64%. From the water balance calculation, it is found that the water is not only formed from biomass moisture content but also dominantly produced from the dehydration reaction during the thermal degradation of cellulose, hemicellulose, and lignin. It is called chemical water which is different from physical moisture water. After BCO water separation by decantation, the oil phase of BCO has a higher HHV than EFB itself (31.68 MJ/kg vs. 16.86 MJ/kg). Still, the oil phase of BCO has a slightly higher viscosity compared to diesel oil. The pH and acid values also indicate that the product is acidic, and this evidence is quantitatively validated by GC-MS analysis. Therefore, downstream processing by visbreaking and water separation is strongly proposed to reduce the viscosity, water content, and acidity of BCO.