Fast Pyrolysis of Peanut Husk Agroindustrial Waste: Intensification of Anhydro Sugar (Levoglucosan) Production

Peanut husks are agro-industrial waste and represent about 20 wt% of the peanut harvest. This waste product was subjected to fast pyrolysis in a pyroprobe reactor coupled with GC/MS at temperatures ranging from 350 to 600 °C to maximize levoglucosan production. Prior to pyrolysis, the biomass was washed with acetic acid (10 wt%) to remove the alkali and alkaline earth metals. Levoglucosan production from pretreated biomass increased for all the temperatures studied. However, the best result was observed at 550 °C. At this temperature, 35 wt% of produced levoglucosan was found in the volatile fraction, representing around a nine-fold increase in levoglucosan production compared to the untreated biomass. These results may be due to the removal of the alkali and alkaline earth metals or the morphological changes observed in the biomass via SEM. While the yields of undesirable compounds derived from lignin that interfere with levoglucosan purification and its applications (phenol, guaiacol, syringol and catechol) decreased as the pyrolysis temperature increased, the yields of other compounds (vanillin, eugenol, cresol, 4-methylcyclohexanone, furfural and acetaldehyde) increased. Our results confirm that pretreated peanut husks have great potential in levoglucosan production via fast pyrolysis. Graphic Abstract