Recycling of residual biomass of medicinal and aromatic plants: A valuable alternative towards bio-refinery

A large amount of residual waste biomass is generated from medicinal and aromatic plants (MAPs) sector that needs to be utilized through effective recycling as resources and to reduce environmental load. In this study, identification of functional groups, surface morphology, nature of crystallinity, thermal property, biochemical (cellulose, hemicellulose and lignin), and elemental profiling (macro and micro nutrients) was carried out in residual biomasses of six aromatic and two medicinal plants to understand their best alternate use as different bio-refinery potential such as bioethanol, biochar, compost, bioactive rich extract, and growth medium. The biochemical and elemental profile provided quantitative data for primary grouping of the biomasses based on their possible usage that was supported by qualitative (or semi-quantitative) data from functional, morphological characterization, analysis of crystallinity and thermal behaviour. The biomass of MAPs like lemongrass, palmarosa, java citronella, isabgol and ashwagandha had higher cellulose and hemicellulose content (structural, crystalline and biochemical information), make them useful for preparing bioethanol. On the other hand, biomasses with high aromaticity and thermal stability in their structure like- holy basil, sweet basil, menthol mint and isabgol, found suitable towards development of biochar. Elemental profile showed suitability of holy basil, sweet basil, menthol mint and isabgol biomass for their composting potential. All biomasses seemed to be useful for growth medium preparation based on biochemical, functional and morphological analysis. Amalgamation of different characterization techniques were found rational to understand the best alternative(s) for residual biomasses. Thus, this study helps to develop a strategy for complete recycling of biomasses under model bio-refinery, which also advocate circular economy.