Biorefining finger millet residues via anatomical fractionation for efficient nanocellulose extraction in a...

The effective utilization of lignocellulosic biomass from underexplored crops is central to advancing sustainable materials and biorefinery processes. This study investigates the productivity and quality of α-Cellulose, Microcrystalline Cellulose (MCC), and Nanocrystalline Cellulose (NCC) extracted from distinct anatomical fractions of Eleusine coracana L. (Finger Millet) i.e. Cob (FM-C), Husk (FM-H), Leaf (FM-L), and Stem (FM-S). Finger millet is an abundantly cultivated yet underutilized cereal crop for material valorization widely cultivated in South Asia and Sub-Saharan Africa. Using standardized sequential acid-alkali treatment and analytical protocols, the study evaluates extraction yields, crystallinity indices, thermal stability, and surface characteristics of the cellulose derivatives. FM-C yielded the highest α-Cellulose (35.89 %) and MCC (95.12 %) productivity, while FM-H exhibited the highest MCC to NCC conversion efficiency (80.93 %). X-ray diffraction confirmed that NCC from FM-C attained the highest crystallinity (55 %), indicating improved structural ordering post-treatment. A cradle-to-gate Life Cycle Impact Assessment (LCIA), aligned with ISO 14040 standards, revealed that the FM-C (216.64 kg CO₂ eq. / kg NCC) is more sustainable in terms of carbon footprint, followed by FM-S (313 kg CO₂ eq. / kg NCC), FM-L (316.91 kg CO₂ eq. / kg NCC), and then FM-H (406.73 kg CO₂ eq. / kg NCC). These findings directly corresponded to lower initial α-Cellulose content and higher processing demands thereof. These insights underscore the importance of biomass fraction selection in optimizing both product yield and environmental sustainability for cellulose-based material applications.