Physiochemical characterization and thermal kinetics of lignin recovered from sustainable agrowaste for bioenergy applications

Abstract

In this study, lignin, one of the commonly occurring natural polymers, is extracted from banana agro-waste. Lignin is recovered from the spent liquor produced during alkaline pre-treatment of agro-waste and precipitated by acidification. This study focuses on the physio-chemical characterization and thermal degradation behaviour of lignin extracted from agro-waste biomass. The extracted lignin yield accounts for nearly 12% of the biomass composition. Spectral analysis, FTIR and NMR explain purity and carbon skeleton characteristics of herbaceous lignin monomers, majorly G and S units. Morphological analysis by SEM showed hollow spherical structures with large surface area for the extracted lignin. The calorific value of extracted lignin was experimentally found to be 21.4276 MJ/kg, which suggests the possible use of extracted lignin as an alternative to sub-bituminous coal. Thermal studies of lignin showed that lignin degrades in a wide temperature range releasing CO2, CH4, H2O, CO and H2. The volatile content of extracted lignin is found to be 31.42%, which suggests its possibility for gasification process. The overall outcome supported that recovered lignin from agro-waste is a potential resource for bioenergy.