Effects of Pyrolysis Conditions on Organic Fractions and Heat Values of Olive Mill Wastes Pyrolysis Liquid

Abstract

Pyrolysis liquids can be evaluated in energy and material recovery. However, its characteristics and recovery potential highly depend on pyrolysis conditions. Olive pomace is lignocellulosic biomasses widely studied in the production of renewable energy and bio-based materials through pyrolysis, but there are no comprehensive studies about changes of pomace pyrolysis liquids' characteristics by pyrolysis conditions. Therefore, in this study, pyrolysis of olive pomace and various combinations of olive pomace with olive mill wastes at different heating rates, temperatures, and retention times was conducted to reveal effects of pyrolysis conditions on pyrolysis liquids' organic fractions. Moreover, heating values of organic compounds in pyrolysis liquids at different pyrolysis conditions were evaluated. All bio-oils comprises of aliphatic compounds (alkanes, alkenes, and alkynes), oxygenated compounds (acids, aldehydes, alcohols, esters, and ketones), and aromatic compounds (phenols and benzenes). The highest percentages of aliphatic compounds in olive pomace bio-oils were obtained at 600 °C, 5 °C/min heating rate with retention. A pyrolysis temperature increment leads to a decrement in H-type phenols and an increment in S-type and G-type phenolic compounds. Mixing pomace with olive mill wastes resulted in aliphatic compounds increment and oxygenated compounds decrement. Heating values of all bio-oils obtained under different pyrolysis conditions were found important for energy production. When pomace pyrolysis liqiuids' heating values changed between 2831 and 5100 cal/g, heating values of pomace-olive mill waste mixtures' bio-oils were found between 3300 and 5500 cal/g. Consequently, organic compounds in both pomace and pomace-olive mill bio-oils are valuable feedstocks and energy source in the number of product productions in various industrial processes.