A Sustainable Solid Waste Management of Aloe vera Processing Industry Through Biorefinery Approach

Aloe vera rind (AVR), a conspicuous solid waste with a significant amount of lignin (16.40 ± 0.67%, w/w) is discarded from the gel processing industries and finds no market value. The complex recalcitrant and heterogeneous nature of AVR lignin prerequisites an efficient treatment strategy for its valorization into value-added chemicals in promoting sustainable lignocellulosic biorefinery. However, the lack of selectivity in most of the treatment strategies hinders the effective AVR lignin valorization for its commercial application. Therefore, in this study, a combinative treatment strategy like microwave-assisted natural deep eutectic solvents (MW-NDES) was opted for the selective valorization of AVR lignin using choline chloride and glycerol. A maximum delignification of about 57.46% (w/w) was obtained after MW-NDES pretreatment (480 W, 10 mins) with a residual lignin of 69.70 mg/g. In addition, an increase in the microwave irradiation power has significantly increased the formation of lignin-derived hydrocarbons in the pretreated liquor by 1.24-fold (320 W) to 1.73-fold (480 W) as compared to the treatment set at 160 W. Further, an alluvial diagram was plotted to depict the depolymerization of AVR lignin into monomers. AVR lignin valorization by greener means of pretreatment could be a suitable biorefinery approach for AVR processing.