The effect of reducing mineral matter naturally present in sawdust from untreated poplar (Populus deltoide) wood and giant reed (Arundo donax) canes on pyrolysis kinetics was examined from comparative non-isothermal thermogravimetric measurements in the range 20-900 degrees C, using raw and previously demineralized samples. Estimated kinetic parameters reflected changes caused by demineralization, especially in the low temperature range (up to approximate to 450 degrees C), likely due to catalytic effects of the minerals. Pyrolysis of the demineralized biomasses also induced an enhanced development in pore structure of the resulting charcoal, favoring its potential use in adsorption applications and/or as an improved intermediate product for further conversion into activated carbons.