High-Lignin Content and Chemical Composition of the Coarse Fraction (>250µm) from Telfairia pedata Hard Shell for Biocomposite Applications

Abstract

Telfairia pedata (Oyster Nut) produces a hard outer shell typically discarded as waste despite its complex microstructure and potential value in material science. During preliminary analysis, the shell was found to comprise two tightly bonded yet visually distinct components: a soft yellowish outer layer and a dense, black inner core. Due to their structural differences, the shell was mechanically ground and manually sieved to obtain size-based fractions that loosely correspond to these regions. The coarse fraction (>250 μm) primarily represents the glassy black inner component, which resisted grinding and separated last during size reduction, making it the densest and most mechanically resilient portion. This study investigates the chemical composition of this fraction to assess its suitability as a functional filler in biocomposites. Duplicate chemical tests revealed the following composition: 12% moisture, 2.46% ash, 3.48% extractives, 48.16% lignin, 25.52% hemicellulose, and 20.38% cellulose. The exceptionally high lignin content highlights this material’s intrinsic rigidity, hydrophobicity, and thermal resistance, key attributes for reinforcing polymeric matrices in applications requiring durability and moisture tolerance. These findings reveal new opportunities to valorize high-lignin agricultural waste as a filler for advanced biocomposites in automotive, construction, or engineering-grade bio-based materials. The coarse fraction’s composition confirms its potential in developing rigid, high-performance, and eco- friendly alternatives to conventional fillers within sustainable material systems.