Sustainable Valorization of Olive Pomace Waste to Renewable Biofuels, Biomaterials and Biochemicals Via Pyrolysis Process: Experimental and Numerical Investigation

Abstract

This work demonstrates, experimentally and numerically, the potential of Olive Pomace Waste (OPW) to produce renewable biofuels (pyrolytic oil and gas), bio-chemicals (tars as source of bioactive molecules) and bio-fertilizers (chars) through slow pyrolysis. Experimental pyrolysis runs were conducted at 500, 600 and 700°C as final pyrolysis temperature, 15, 20 and 25°C/min as heating rate and 1h as residence time, in a fixed bed pyrolyzer. In the optimum pyrolysis conditions (600°C and 15°C/min), 33 wt.% of oil, 30.00 wt.% of char and 37 wt.% of gas were produced. Recovered pyrolytic oil presents good energy value (HHV between 15.96 and 20.94 MJ/kg) with a great bioactive potential. The released permanent gases show an interesting energy content (LHV up to 11 MJ/Kg) which emphasizes their application in a gas engine to provide renewable electricity in rural olive groves area. The recovered OPW biochar presents a high carbon (C 72.54 wt.%) and nutrients contents (up to 8.42 mg/g of Ca, up to 8.69 mg/g of K and up to 2.02 % of total N) which make it suitable for soil amendment and for long-term carbon sequestration. Kinetic study of OPW pyrolysis, performed using the Distributed Activation Energy Model (DAEM), gives an activation energy values ranging from 121.6 to 151.6 kJ/mol. The investigation of the OPW thermal behavior and reactivity under pyrolysis conditions is useful approach to design and operate slow pyrolysis process at commercial scale, which could be useful by farmers for OPW in olive fields.