Catalytic Valorisation of Sugarcane Bagasse to Energy Carriers

Sustainable processes have continued to be of interest to both academia and industries. The sugar industry in this regard has explored the potential of using sugar cane bagasse as a fuel within the industry so as to enhance the economics of the process. In addition to its fuel potential, bagasse has the prospects of being converted to chemical compounds that could serve as both raw materials as well as energy carriers. In this work, we investigated the potential of adding value to sugarcane bagasse by catalytic and non-catalytic thermal conversion processes; hydrothermal liquefaction (HTL) and pyrolysis. HZSM-5 was used as a catalyst for both the hydrothermal liquefaction and pyrolysis processes. The HTL operating temperature and heating times were varied between 220–373°C and 30–60 mins respectively while the catalyst type, reactor volume loading and feedstock to water ratio remained fixed. The pyrolysis was carried out at temperatures of 400°C, 450°C and 500°C and the effect of catalyst to biomass (0.1:1 g/g, 0.25:1 g/g and 0.5:1 g/g) on the product yield and distribution was also investigated. The results showed that various compounds were obtained as the hydrothermal conditions were varied. Interestingly, the aliphatic hydrocarbons were relatively lower in concentration when compared to the substituted hydrocarbons. The highest amount of hydrocarbons (a little over 6 wt. %) was obtained when the bagasse was hydrothermally converted using a catalyst at 300°C for 45 minutes. Esters accounted for about 80 wt. % when the process was carried out at 373°C and 45 minutes in the presence of ZSM-5, this is more than double the amount obtained when the same conditions were used in the absence of a catalyst. Findings from this study also revealed that the bio-oil yield was significantly affected by pyrolysis temperature and catalyst to feedstock ratio. A higher yield of pyrolytic bio-oil and higher conversion of sugarcane bagasse was produced with the HZSM-5 catalyst when compared to the non-catalytic pyrolysis process. Aromatization of produced bio-oil was enhanced by the higher catalyst loading during the pyrolysis of sugarcane bagasse.