The Valorization Potential of Kolanut Pod for Biogas Production: A Physicochemical and Biochemical Characterisation

Abstract

This study evaluated kolanut pod as a potential biomass for biogas production in an anaerobic digestion process. Fresh kolanut pod underwent mechanical pre-treatment process of washing, sun-drying and pulverised with a Janke and Kunkel hammer mill for particle size reduction. The Dry Matter (DM), Organic Dry Matter (ODM), Organic Carbon (OC) and Nitrogen (ON) and calorific value of the residues were determined by APHA standard method. Its morphological structure and elemental composition were determined using the methods of Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX), The functional group and microbial characterisation were determined using Fourier transform infrared spectrometry (FTIR) and Bergy's Manual of Bacteriology, respectively.

The proximate analysis showed that the dry matter and organic dry matter of kolanut pod are 91% and 83%, respectively while ultimate analysis revealed that its organic carbon, nitrogen and calorific value are 14.25%, 0.46% and 3.6512 kJ/kg, respectively. The kolanut pod showed irregular and heterogeneous surface morphology with well-developed porous structures that appear as little cavities. The kolanut pod also revealed a particle size of 20.36 ?m, height of 2.41 mm with bulk density of 2.12 g/cm³ while the EDX showed presence of essential macro-elements such as Silicon, Si (22.15%), Calcium, Ca (13.96%), Potassium, K (3.29%), Aluminum, Al (1.98%), Magnesium, Mg (2.35%) and Sodium, Na (0.28%). FTIR revealed a characteristic peaks indicative of cellulose, lignin, and phenolic compounds The anaerobic bacterial present in the kolanut pod are Bacillus cereus, Escherichia coli and Proteus mirabilis.