From the simulation studies, optimal operating conditions, maximizing hydrogen production and thermal efficiency, are revealed in Table 2. In this study, it is assumed that 100% purity of hydrogen can be produced from the separation unit. The optimal hydrogen products of each biomass are shown in Table 3. The results indicated that rice straw can produce the maximum hydrogen yield, while cassava root has the highest thermal efficiency. Since biomass heating value directly affect the thermal efficiency,a lower heating value has higher thermal efficiency, such as cassava root.
Moreover, an energy recovery technique is also applied for improving the biomass gasification efficiency. In this process, gas streams produced from the reformer and shift reactor units have high temperature, and the temperature of these streams have to be reduced before flowing into another unit. Therefore, waste energy occurs in the reformer and shift reactor gas streams. The waste energy can be recovered as partial energy input for the reformer unit as shown in Fig. 2. In addition, thermal efficiency of energy recovery-biomass gasification process is presented in Table 4. The results revealed that when energy recovery is used, thermal efficiency of hydrogen production from all biomass types can be increased, especially for cassava root that increased by 14.74%.