Pretreatment–gasification coupling for agro-residue conversion: Insights from experimental and Aspen plus simulations: Insights from experimental and Aspen plus simulations

Phosphoric acid pretreatment has emerged as a promising strategy to enhance the thermochemical conversion of lignocellulosic biomass, particularly for hydrogen-enriched syngas production. This study evaluates the effects of a 5 wt% phosphoric acid treatment on two underutilized agro-industrial residues—coffee husk and sugarcane bagasse—prior to downdraft gasification. Pretreatment was conducted under mild thermal conditions (60 °C) with variable residence times, and its impact was assessed through proximate and elemental analysis, Van Krevelen diagrams, higher heating value (HHV), and gasification performance metrics including hydrogen yield, syngas composition, and cold gas efficiency (CGE). Experimental results were supported by simulations in Aspen Plus. Coffee husk showed a marked improvement in carbon and hydrogen content, HHV, and syngas quality. Hydrogen concentration nearly doubled, and CGE increased by over 25 %, confirming the pretreatment's effectiveness in disrupting the recalcitrant structure and enhancing devolatilization. In contrast, sugarcane bagasse exhibited a limited and heterogeneous response, with decreased hydrogen output and increased ash content likely due to phosphate precipitation and catalyst passivation. These findings highlight the importance of feedstock-specific strategies in biomass valorization and support the integration of phosphoric acid pretreatment as a low-corrosivity, circular solution for improving hydrogen-oriented gasification. The dual valorization of agricultural residues and industrial by-products aligns with sustainable energy and resource efficiency goals. Further research is recommended to optimize pretreatment conditions and explore hybrid strategies for ash-rich feedstocks.