Effect of heating rate on hydrothermal liquefaction of Moroccan two-phase olive mill waste (alperujo)

Two-phase olive mill waste ( TPOMW ), also known as alperujo , is generated in large quantities and presents serious environmental issues due to its high organic load, acidic pH and elevated polyphenol content. In this work, hydrothermal liquefaction (HTL) is investigated as a pathway to valorize Moroccan TPOMW into bio-oil and hydrochar. Batch experiments were conducted at temperatures between 260 and 300 °C, reaction times from 0 to 30 min, and two heating rates (5 and 60 °C.min −1 ). Product distributions (bio-oil, hydrochar and gas) were determined, and the physicochemical properties of the condensed products were characterized by elemental analysis, Fourier transform infrared ( FT-IR ) spectroscopy and GC-FID/MS . Higher heating values ( HHVs ) and overall energy yields were also evaluated. Increasing temperature and reaction time under fast heating enhanced the bio-oil yield, which reached a maximum of 43.7 wt% at 300 °C and 30 min, while the hydrochar yield decreased to 14.6 wt%. Fast heating favored bio-oil production, whereas slow heating promoted hydrochar formation as a result of the extended heat-up period and secondary repolymerization reactions. The highest overall energy yield, 94%, was obtained at 300 °C and 30 min under fast heating. These results highlight the critical influence of heating rate, temperature and reaction time on HTL product distribution and energy recovery and provide guidance for the design and optimization of HTL processes for wet lignocellulosic residues such as TPOMW . • Heating rates strongly affect hydrothermal liquefaction of two-phase olive mill waste. • Fast heating raises bio-oil yield to 43.7 wt% at 300 °C. • Slow heating favors formation of energy-dense hydrochar. • Fast heating achieves up to 94% overall energy recovery. • Most feed carbon is retained in bio-oil and hydrochar rather than gas.