The contents of these three gases increased simultaneously at different rates, reaching the maximum values at about 22 min during the gasification process. Notably, in the AHH group, a pre-peak appeared before the main peak of CO and CO2, indicating incomplete carbonization of AHH during pyrolysis process, and this material requires longer pyrolysis time than ZMS and ADR. Additionally, among three feedstocks, AHH showed slightly higher hydrogen-releasing efficiency (0.912 L/g) than ZMS (0.882 L/g) and ADR (0.834 L/g) (Table ). To comparatively investigate the advantage of pyrolysis treatment before gasification, the non-pyrolyzed feedstocks (ZMS, ADR, and AHH) were directly heated to 900 o C with a steam supply of 5 mL/min. As the profiles of syngas shown in Fig. , pre-peaks of CO and CO2 appeared at around 20 min, indicating that feedstocks were carbonized before the release of hydrogen. The carbonaceous gas and hydrogen from non-pyrolyzed feedstocks and biochar were quantitatively analyzed and shown in Table . For all three feedstocks, the hydrogen yield was higher in the biochar group than in the non-pyrolyzed group. For AHH, the hydrogen yield increased by 10.36% with the pyrolysis treatment of the raw feedstock (Table ). Moreover, for ZMS and AHH, pretreatment of pyrolysis also improved the ratio of CO2 to CO, which indicated a more thorough conversion of carbon materials. These findings suggested that pyrolysis pretreatment effectively improved hydrogen production efficiency and pollution reduction in biomass gasification.