Biochar from Slow Pyrolysis of Two-Phase Olive Mill Waste: Effect of Pressure and Peak Temperature on its Potential Stability

Abstract

The present study examines the effect of both the pressure and peak temperature on the potential stability of the biochar produced from the slow pyrolysis of two-phase olive mill waste. On the basis of the available studies in the literature, the following properties were taken as rough indicators of the potential stability of biochars in soils: the fixed-carbon yield, the fraction of aromatic C, and the molar H:C and O:C ratios. Pyrolysis experiments were performed in a laboratory-scale fixed-bed device and planned following a central composite design. The product gas yield and composition values at the outlet of the secondary cracking reactor (a fixed-bed of activated alumina particles at 700 °C) were also analyzed as a function of pressure and peak temperature. The results from the statistical analyses indicate that both the analyzed factors have a strong influence on the distribution of the pyrolysis products, as well as on the properties of the produced biochar. The most potentially stable biochars w...