A detailed evaluation of the structure of biochar from slow pyrolysis of elephant grass during its steam gasification was performed. The effects of surface area and inherent alkali and alkaline earth metal (AAEM) species on the reactivity of the biochar were investigated. Drastic changes in biochar structure occurred throughout the reaction, especially for low degrees of conversion. The BET surface area of the biochar increased significantly until the conversion reached 0.49, and there was a steep decrease at high degrees of conversion. The biochar showed a high AAEM concentration. The aromaticity of the biochar suggested an ordered carbon structure that can lower the reaction rate. The high syngas yield makes the process attractive for generation of renewable energy.