Characterization of crop residues from false banana /Ensete ventricosum/ in Ethiopia in view of a full-resource valorization

Abstract

False banana / Ensete ventricosum [Welw.] Cheesman/ is exploited as a food crop in Ethiopia where it represents an important staple food. The plant is harvested and large amounts of biomass residues are originated, mainly from the pseudo stem (i.e., fiber bundles obtained from the leaf sheaths after being scrapped to produce starchy food) and the inflorescence stalk. These materials were studied in relation to their summative chemical composition, composition of lignin, lipophilic and polar extracts. Moreover, their structural characteristics, in view of their valorization, were scrutinized. The analytical studies were performed with the aid of FTIR, GC/MS, Py-GC/MS and SEM. The fiber bundles are aggregates of mainly long and slender fibers with low ash, extractives and lignin contents (3.8%. 4.4% and 10.5% respectively) and high holocellulose and α-cellulose contents (87.5% and 59.6% respectively). The hemicelluloses in the fibers are mostly highly acetylated xylans and the lignin is of the H-type (H:G:S, 1:0.7:0.8). This lignin composition is in line with the FTIR peaks at 1670 cm ^-1 and 1250 cm ^-1.The inflorescence stalk has high ash content (12.3% in the main stalk and 24.6% in fines) with a major proportion of potassium, high extractives (25.9%), and low lignin and α-cellulose contents (5.8% and 17.9% respectively). The stalk includes numerous starch granules in the cellular structure with the predominant presence of parenchyma. The potential valorization routes for these materials are clearly different. The fiber bundles could be used as a fiber source for paper pulp production with the possibility of a prior hemicelluloses removal while the inflorescence stalk has nutritional value for food and fodder. Furthermore, it can also be used for sugar fermentation products.