Physicochemical characterization, valorization of lignocellulosic waste (Kola nut seed shell) via pyrolysis, and ultrasonication of its crude bio-oil for biofuel production

Abstract

Kola nut seed shell is a largely generated food waste that can be explored as an alternative energy source to reduce the damaging effects of the combustion of fossil fuels on the environment and reduce its usage since it’s limited in nature. The seed shell’s proximate and ultimate data were obtained using standard procedures; ash deposition indices were obtained using XRF data; crystallinity of its cellulosic component was determined using XRD data; pyrolysis was done using a fixed bed pyrolyzer; and ultrasonication of crude bio-oil and its alcoholic blends was done using an ultrasound bath rated at 55 W. Its shell has moderate Moisture Content (MC) (5.84%), high C (51.92%), low amounts of S (0.020%), N (0.11%), ash content (5.26%), high VM (84.85%), Fixed Carbon (FC) (4.05%), C/N (472), H/C (0.096), and Higher Heating Value (HHV) (17.23 MJ/kg). Its mass ratio combination gave the empirical formula CH_0.096O_0.82N_0.002. It pyrolytically degrades at a thermal temperature range of 400–550 °C. XRF analysis of its ash base on Na₂O+K₂O/SiO₂ was 0.0897, which means no sintering inclination; B/A (0.27, low ash deposition tendency); SiO₂/Al₂O₃ (22.92) and Fe₂O₃/CaO (0.135) (low and high ash deposition tendencies, respectively); slagging viscosity index (83.48, high slagging tendency); %SiO₂ (71.52); babcock (Rs, 5.4 × 10⁻⁵); fouling indices (1.7 × 10⁻², low deposition tendencies); and total alkalis (0.0642, low fouling tendency). GC and FTIR of the upgraded bio-oil showed complex compounds suitable as biofuel. Its co-pyrolysis with other biomass could reduce fouling, sintering, ash, and corrosion issues.