Comprehensive pyrolysis investigation of Lemongrass and Tagetes minuta residual biomass: bio-oil composition and biochar physicochemical properties

The generation of spent aroma plant/process waste is increasing due to the growth of the essential oil industries due to the demand for essential oils. This study aims to convert such spent aroma plant waste, i.e., spent Lemongrass and Tagetes minuta, into bio-oil and biochar using slow pyrolysis. In this work, pyrolysis is conducted at different temperatures (350–500 ℃) at a heating rate of 10 ℃/min in a nitrogen atmosphere with a 50 mL/min flow rate. The maximum bio-oil yield obtained for Lemongrass was 37.3 wt% with a biochar yield of 31.6 wt% at 400 ℃; however, in the case of Tagetes minuta, the maximum bio-oil yield (39 wt%) was observed at 450 ℃ with 27.3 wt% of biochar yield. GC-MS analysis of bio-oil indicated its phenolic-rich nature along with other functionalities, i.e., carbonyls, furans, N-containing, and other types. Maximum phenolics observed with 60.27 area% for Lemongrass and 62.75 area% for Tagetes minuta at 450 ℃. Finally, to understand the breaking patterns of the biomass framework, flash pyrolysis through the analytical instrument, Py-GC/MS, was carried out at a high heating rate of 20 ℃/ms.

Graphical abstract