Hydrogen and Bio-oil Production from Diverse Biomass Through Microwave-assisted Pyrolysis

Abstract

Hydrogen production from lignocellulosic biomass (rice husk (RH) and saw dust (SD)) and macroalgal biomass (Kappaphycus alvarezii (KA) and Eucheuma spinosum (ES)) through pyrolysis has been studied using a lab- scale microwave reactor. The reactions were carried out at 800 W and 800 °C using activated carbon as susceptor to evaluate the potential of biomass for hydrogen production. Elemental analysis and proximate of the feedstocks were performed and the pyrolysis products were thoroughly characterized. Higher heating value of the biomass (in MJ kg^-1) follows the trend: SD (25.2) > RH (14.6) > KA (8.7) > ES (7.8). Thermogravimetric data shows that the maximum decomposition temperature follows the trend: SD (362°C) > RH (340°C) > KA (197°C) > ES (178°C). The gaseous yield from microwave pyrolysis was maximum from SD (39 wt.%) and minimum from ES (33 wt.%), while the bio-oil yield was highest from SD (33 wt.%) and lowest from RH (25 wt.%). The hydrogen yield from biomass follows the trend: SD (28 vol.%) > ES (27 vol.%) > RH (26 vol.%) > KA (24 vol.%). The H₂:CO (mol/mol) ratio was: SD (0.94) > RH (0.81) > ES (0.73) > KA (0.59). The bio-oil from KA and ES mainly contains linear oxygenates (~53%), while the bio-oils from RH and SD were rich in phenolics (58-77%).