Pyro-gasification of olive pomace pellets for renewable hydrogen production: experimental data-driven techno-economic analysis

The increasing demand for sustainable energy solutions has intensified research into renewable hydrogen production from biomass. This study investigates the pyro-gasification of olive pomace pellets, i.e. a by-product of the olive oil industry, to generate hydrogen through an integrated thermochemical process. Experimental tests were conducted at 900 °C in a rotary kiln reactor across varying equivalence ratios (ER) ranging from 0 (pyrolysis) to 0.28 (gasification). The resulting syngas compositions were used as inputs for process simulations in Aspen Hysys, where a data-driven modelling approach enabled the integration of experimental reactor outputs into the wider plant-scale assessment, encompassing steam methane reforming, water-gas shift reactions, and hydrogen purification via pressure swing adsorption. Results demonstrated that increasing the ER reduced char yields and tar content while enhancing syngas production. However, a non-monotonic trend in hydrogen output was observed, with the highest annual production (around 512.8 tons/year) and maximum thermochemical efficiency of 47.3% achieved at ER = 0.1. At this condition, the levelized cost of hydrogen was minimized to 16.30 €/kg, reflecting an optimal balance between partial oxidation and gasification reactions. Sensitivity analysis further revealed that reformer temperature significantly influences hydrogen yield, plateauing beyond 850 °C. Overall, the findings confirm that olive pomace pyro-gasification, under controlled oxidant supply, constitutes a technically and economically viable route for renewable hydrogen production. This work provides a robust foundation for scaling up biomass-based hydrogen systems and supports the valorisation of agro-industrial residues within a circular bioeconomy framework.