Effect of Temperature on Slow Pyrolysis of Pellets from Solid Waste of Sugar Palm Flour Industry for Bio-Oil Production

The sugar palm flour industry generates substantial solid waste, contributing to environmental pollution. The utilization of waste pellets as raw material for pyrolysis for bio-oil production has not been widely studied. Pelletization aids handling and improves pyrolysis efficiency through uniform size and density. This study investigated the effect of pyrolysis temperatures of the pellets on the yield and quality of the produced bio-oils. Pyrolysis was carried out non-isothermally with a heating rate of 40°C/min, starting at room temperature and continuing until the final temperature was reached, which was varied at 300°C, 400°C, and 500°C in an N 2 atmosphere. The condensed vapor was then collected in a closed container and subjected to several analyses, including yield, viscosity, density, pH, calorific value, and chemical composition. Results show that the optimal temperature was 400°C, at which the bio-oil exhibited the highest yield (43.8% wt), the lowest viscosity (2.05 cSt), the highest density (1.138 g/mL), and a sufficient calorific value (1.0 kcal/g on a wet basis). Gas Chromatography-Mass Spectrometry analysis revealed that the acidic compounds (phenolics and carboxylic acids) in bio-oil increased with increasing pyrolysis temperature. Higher temperatures increase bio-oil yield by breaking down biomass components, such as lignin. However, excessive heat causes the thermal cracking of the produced organic vapors, thereby reducing yield and increasing acidic compounds. Our novel study presents new opportunities for utilizing pelletized biomass waste-derived bio-oil as a biofuel. However, improving bio-oil quality—particularly by reducing acidity and increasing calorific value—may require upgrading techniques such as catalytic pyrolysis, which should be explored in future research.