The concentrations of alkali, alkaline earth and heavy metals of
the bottom ashes and their extractions measured by ICP-OES are
presented in Table 2. The results clearly show that both PWG
and 20SWCG bottom ashes mainly contain alkali and alkaline earth
metals, i.e. K, Na, Ca, and Mg as the major components, which contributes
to the high basicity (pH valves ranging from 9.2 to 13.4) of
these two bottom ashes. This result is in good agreement with the
data reported in previous studies regarding ash originated from
wood gasification (Gori et al., 2011; Tafur-Marinos et al., 2014)