Compositional Chemical Property Analysis and Evaluation of Liquid Smoke Produced from Microwave-Assisted Pyrolysis of Binary Mixtures of Oil Palm Solid Waste

Abstract

Microwave-assisted pyrolysis of oil palm solid waste at 300°C and 400°C was conducted to examine synergistic effects on liquid smoke yields for binary mixtures and allow examination of the produced chemical compounds. Pyrolysis of mixtures of empty fruit bunches and kernel shells (EFB/KS) led to the highest yield, of almost 25% at 300°C for an EFB-to-KS ratio of 80:20, while the yields at 400°C remained relatively similar for any ratios. In contrast, the yields were minimal at around 4% for an EFB-to-mesocarp fibres (MF) ratio of 80:20 and 17% for an EFB-to-MF ratio of 50:50 at 300°C and 400°C, respectively, in EFB/MF pyrolysis. In EFB/fronds-trunks-leaves (FTL) pyrolysis, the yields were slightly higher at 400°C than at 300°C and relatively unchanged at any EFB-to-FTL ratios. For most liquid smoke, GC–MS analysis exhibited that phenolic compounds dominated the chemical compositions of the liquid smoke. Based on this finding, the optimal liquid smoke in terms of yield and phenolic compound percentages was from pure KS pyrolysis. This work successfully demonstrated the benefit of utilising microwaves and the synergistic effects of binary mixtures on yields and product distribution and improving the quality of the products.

Keywords: Pyrolysis, microwave, oil palm, liquid smoke, agricultural waste