Enhancing the potential for producing hydrogen-rich syngas through the steam gasification of low-value agro-industrial residues with torrefaction

Steam gasification is a highly effective method for producing hydrogen (H2) and represents a key valorization route for agro-industrial residues. In this scenario, the objective of the current study was to investigate the effect of torrefaction on the steam gasification of low-value agro-industrial residues, focusing on enhancing H2 content in syngas. Kinetic parameters were estimated, and syngas was quantified using macro-TGA/GC-TCD/FID. Torrefaction was performed under light (200 degrees C, 15-60 min), mild (250 degrees C, 15-60 min), and severe (300 degrees C, 15-60 min) conditions. The results revealed that torrefaction enhances H2 content in syngas, with the H2 molar fraction peaking at 62 % under severe conditions. Specifically, the H2 molar concentration increased across all severities except for passion fruit peel waste at severe conditions, where a decline was observed. Ponkan peel waste showed a consistent rise in H2 molar concentration at all torrefaction severities, with the most significant increase in the lower heating value of syngas. Additionally, torrefaction improved syngas composition by reducing the CO2 fraction and increasing the CO fraction, thus enhancing the overall lower heating value of the syngas. The kinetic study, utilizing the Modified Random Pore Model (MRPM), demonstrated precise fits and provided reliable predictions for the impact of torrefaction on steam gasification. The reduction in rate constants suggests improved surface reactions and greater structural stability in gasification kinetics. The findings from this study support the adoption of torrefaction as a promising pre-treatment method to optimize biochar properties and maximize hydrogen-rich syngas production from low-value agro-industrial residues.