ER is a crucial parameter affecting gasification temperature and the composition of producer gas. It is defined as the fuel-to-air weight ratio used divided by the fuel-to-air weight ratio of stoichiometric combustion. Gasification temperature profiles of mesquite and juniper sample were measured under four different ER conditions: 2.7, 3.2, 3.7, and 4.2. It can be seen from the Figs. 7 and 8 that Tpeak increased with the decrease of ER. This was because a lower value of ER means more amount of oxygen supplied to the gasifier. A high air flow rate promoted the oxidization reaction which results in more heat release and temperature raise in the gasifier