Catalytic Influence of Locally Derived Iron on Product Profiles and Energy Efficiency in Shea Nut Cake Hydrothermal Liquefaction

The increasing depletion of fossil fuel reserves, rising costs, and the damaging effects of greenhouse gas emissions have driven the search for alternative energy sources. Hydrothermal liquefaction of agro-waste, such as shea nut cake, offers a sustainable solution by reducing emissions, diversifying resources, and better utilizing low-value biomass. This study aimed to produce high-quality biocrudes from the hydrothermal liquefaction of shea nut cake (SNC) residue at temperatures from 280 to 400 °C, using Fe 2 O 3 as a low-cost catalyst. The SNC cake, with 65 % carbon, 61.24 % volatile matter, and a calorific value of 14.34 MJ/kg, shows good potential for thermochemical conversion. Its high carbon and volatile content enhance reactivity and bioenergy yield, making it a viable feedstock for sustainable energy production. The chemical structure of SNC cake exhibits functional groups comparable to those present in typical biomass materials. During catalytic HTL, Fe 2 O 3 facilitates the formation of biocrude rich in nitrogen- and oxygen-compounds. The GC-MS analysis of the biocrude revealed the presence of light benzene derivatives, phenolic compounds, and hydrocyclic molecules. These compounds indicate partial depolymerization of lignin and cellulose during catalytic HTL, suggesting that Fe₂O₃ effectively promotes the breakdown of complex biomass macromolecules into valuable nitrogen- and oxygen-containing bio-oil components. The thermal biocrude exhibited a higher heating value of 15.83 MJ/kg and a lower carbon content, whereas the catalytic HTL process enhanced fuel quality, increasing the carbon content to 63.53 wt.% and raising the higher heating value to 16.66 MJ/kg. This demonstrates that Fe₂O₃ effectively improves both the energy density and overall quality of the biocrude. Overall, these results show that Fe2O3-catalyzed hydrothermal liquefaction of shea nut cake is an effective and sustainable method for producing higher-quality biocrude with greater carbon content and energy value, demonstrating its strong potential for renewable fuel production and agro-waste valorization.