Agricultural Waste to Clean Green Transport Fuel: Catalytic Hydrothermal Reforming of Pyrolysis Oil From Bagasse

Abstract

Throughout the current century, the global community has encountered significant challenges in curbing the increase in global temperatures to below 2 °C above pre-industrial levels. Additionally, efforts have been made to further restrict the increase to approximately 1.5 °C due to the impact of global warming resulting from the emission of CO2 from the limited fossil fuel reserves. The use of sources of renewable energy, such as biomass, with net zero CO2 emissions into the atmosphere would be vital to the quest for global warming mitigation. The aim of this research was to enhance the quality of bio-crude oil originating from fast pyrolysis of bagasse waste to a higher energy density fluid fuel source capable of being refined into liquid transport fuel using the current existing refinery infrastructure or an alternative cost-effective set-up. Bagasse and bagasse pellet feedstocks from Western Kenya were subjected to a fast pyrolysis procedure in a batch reactor at 500 °C to assess their potential for production of biocrude oil. The produced oil was catalytically hydro-treated in a 50 mL high-pressure sealed batch reactor vessel at 250 °C and 300 °C using formic acid as a hydrogen source and 5% noble metal catalysts, Pt/γAl2O3 and Pd/γAl2O3. A different trial was also conducted using ethanol as a hydrogen source and a Pt/ZrO2 catalyst. Biomass feedstock, bio-crude oil and hydrotreated bio-oil were characterised for feedstock viability, quality evaluation of the other materials and assessment of the processes. The results suggest that bagasse and its processed components may be effectively utilised as solid fuel and for the production of bio-oil (yielding 42–46%) through fast pyrolysis. Bagasse bio-crude oil exhibits promise as a sustainable raw material for transportation fuel and other specialised chemicals, based on its chemical composition and the results of a catalytic reformation process. Analysis results indicate that the final hydrotreated oil products had better heating performance, decreased oxygen and water contents, improved acidity and density, and improved miscibility with other hydrocarbon fuels (fossil fuels). Pt/γAl2O3, Pd/γAl2O3 and Pt/ZrO2 hydrotreated oil products had superior qualities that were comparable to those of conventional fuel oils.