Biomass fast pyrolysis and in line Steam Reforming (SR) is a potential alternative to produce hydrogen. The addition of a sorbent such as CaO in the reforming process allows capturing in situ the CO2 produced and shifting the equilibrium of the reactions involved towards the products, thus leading to higher H2 production and purity. A thermodynamic equilibrium analysis by means of Gibbs free energy minimization method was performed to delimit the range of best operating conditions and assess the impact of Sorption Enhanced Steam Reforming (SESR) strategy on hydrogen production and purity, as well as on reaction enthalpy. A wide range of reforming operating conditions were studied with respect to temperature (300–800 °C) and Steam/Biomass (S/B) ratio (0–4), and the conventional SR was compared with the SESR processes. The SESR simulations were developed by adding the stoichiometric amount of calcium oxide (sorbent) required to capture all the CO2 produced when full conversion of the volatile stream was attained in the SR process. In the SESR, a H2 production of around 12.4 wt % (by mass unit of the biomass in the feed) and a H2 purity higher than 98 vol % were obtained at temperatures in the 400–600 °C range and S/B ratios in the 1.5–3 range. In the SR, a H2 production close to 11.8 wt % and a purity of 67.3 vol % was attained in the 550–650 °C range with a S/B ratio of 4. The SESR allows operating at lower temperatures and S/B ratios, thereby reducing energy requirements and, at the same time, attaining better performance than the conventional SR in terms of H2 production and purity. This work was carried out with the financial support of the grants PID2022-140704OB-I00 and PID2023-147671OB-I00 funded by MCIU/AEI/10.13039/501100011033 and “ERDF, a way of making Europe”, the grants TED2021-132056B–I00, PLEC2021-008062 and CNS2023-144031 funded by MCIN/AEI/10.13039/501100011033 and “European Union NextGenerationEU/PRTR”, the grant PID2022-139454OB-I00 funded by MCIN/AEI/10.13039/501100011033 and the grants IT1645-22 and KK-2023/0060 funded by the Basque Government. Pablo Comendador is also grateful for the PhD grant FPU20/03393 funded by the Spanish Ministry of Science, Innovation and Universities.