The disposal of biomass waste is of great economic and environmental importance because it can be considered as a sustainable and renewable source of energy. Biomass waste can be converted into H2-rich fuel gas quickly by low temperature catalytic gasification technology. In the paper, fowl manure, a typical biomass waste, was pretreated by washing and the properties of the manure sample before and after pretreatment was investigated. The properties of the manure samples prepared depend strongly on washing method. Nearly all the minerals were removed from the waste by the treatment in the sequence of dilute HCl acid and HF acid washing. The difference in the pyrolysis behaviors of the samples before and after acid washing was ascribed to the changes in the organic components and the minerals present in HC during the pretreatment. A distinct catalytic effect of the minerals contained in CM on its pyrolysis behavior was observed.