Valorization of flax shives biomass is investigated through pyrolysis and in-line catalytic hybrid reforming. We demonstrate that this approach enables the conversion of the biomass into three valuable products namely syngas, biochar, and bio-oil while reducing the emissions of greenhouse gases (CH4 and CO2). Given the increasing attention to syngas and especially hydrogen, pyrolysis and reforming reactor parameters were adjusted to enhance syngas production. Analyzed biochar properties such as contents of carbon (>82%), oxygen (<5%), and hydrogen (<1.5%) are conform to the European Biochar Certificate. The bio-oil composition analysis showed that the main compounds were benzene, toluene, phenols, guaiacol, syringol, furfural, and some polycyclic aromatic hydrocarbons, which were converted to lighter species by the reforming. Among the catalysts tested (cobalt, nickel, and cobalt-nickel supported on alumina beads), nickel provided the highest H2 production (8.26 mmol/gdry biomass or 37.41 vol.%). Nickel loading was varied from 0 to 25% with a maximum H2 production obtained with 20%Ni/Al2O3 (11.17 mmol/gdry biomass or 40.13 vol.%). Increasing the reforming temperature from 650 to 800°C enhanced the gas formation (53 wt.%) and the conversion rates of CH4 (62.6%) and CO2 (48.3%). An aging test was also performed on the 20%Ni/Al2O3 revealing a drop in the catalyst activity and stability. The catalysts characterization was realized by determining their porosity, specific surface area, weight loss, and SEM images. It revealed that sintering and carbon deposition are the main reasons behind their deactivation.