This work aims to evaluate the use of bottom biomass ash as an alternative raw material in porcelain stoneware bodies. For this purpose, ash coming from a biomass thermoelectric power plant in Emilia-Romagna (Italy) was selected and its chemical, mineralogical and thermal properties determined. Data indicated its technological role as a flux, so it was introduced in a porcelain stoneware batch in partial replacement of feldspars and experimented at laboratory scale. A bottleneck, relative to the rheological behavior of the slips, was overcome by a slight deflocculant increase. The powder compacts were fired from 1000° to 1220 °C in order to follow the evolution of the technological properties, phase composition (XRPD-Rietveld) and microstructure (SEM). The introduction of ash allowed to lower the firing temperature by 20 °C, while keeping the technological properties comparable with those of the benchmark. Moreover, the mineralogical and microstructural data revealed different sintering kinetics.