During low temperature gasification process of livestock manure, combustion of manure char feedbacks energy for the gasification reactions. The purpose of the present study is to determine the effect of mineral matters on the reactivity of manure char. The chars were prepared from pig and hen composts pretreated by different washing methods. The results show that the oxidation behavior of the manure char is affected greatly by the pretreatment process employed. Oxidation reactivity of the char from raw manure is much higher than that from de-mineralized manure sample. A good correlation between char reactivity and ash content was obtained. The difference in the char reactivities should be attributed to the presence of catalytically active inorganic constituents, especially Ca species. (C) 2010 Elsevier Ltd. All rights reserved.