Experimental and Thermodynamic Assessment of Caryocar Brasiliense (Pequi) Stone for Hydrogen Production via Supercritical Water Gasification

Abstract

The growing demand for sustainable energy carriers highlights hydrogen as a key component in the global energy transition. This study investigates Caryocar brasiliense (pequi) stone as a renewable feedstock for hydrogen production via supercritical water gasification (SCWG). Experimentally, the biomass was characterized through proximate and ultimate analyses, higher heating value determination, and Fourier-transform infrared spectroscopy (FTIR). The results indicate that pequi stone exhibits low moisture content (6.74%), high volatile matter (91.31%), favourable H/C (1.63) and O/C (0.51) molar ratios, and a chemically labile lignocellulosic structure rich in oxygenated and hydrogen-containing functional groups, confirming its suitability for thermochemical conversion. Complementarily, thermodynamic equilibrium simulations were performed using the TeS v3 free software under isothermal (Gibbs energy minimization) and adiabatic (entropy maximization) conditions. The simulations confirm the feasibility of hydrogen-rich gas production from pequi stone, with hydrogen molar fractions exceeding 50% under both isothermal and adiabatic operation, particularly at elevated temperatures and low biomass loadings. Overall, the combined experimental characterization and thermodynamic assessment demonstrate that pequi stone is a promising biomass for sustainable hydrogen production via SCWG, reinforcing its potential relevance for decentralized energy strategies in biomass-rich areas such as the Amazonian region of Maranhão, Brazil.