Sonobe and Worasuwannarak (2008) reported that alkali and alkaline-earth metals play an important role in the catalytic reactions during the biomass pyrolysis. Therefore, from the activation energy results reported in this work allied to chemical composition, the acid treatments using either milder inorganic or organic acid solutions were effective at removing impurities like metal oxides, except silica, and also water treatment was effective on cateto rice husk.