The rice husk combustion in a bubbling and atmospheric fluidized bed reactor was investigated. The results showed the technical viability of producing both heat and amorphous silica from a renewable energy source. This paper presents the characterization of rice husk ash (RHA) obtained under varying fluidization velocities (0.13-0.15 m/s) and rice husk feed (4.5-7.2 kg/h). Characterization techniques include X-ray fluorescence, X-ray diffraction, particle size distribution and scanning electron microscopy. For the employed range of fluidization velocities of rice husk feed no noticeable influence on the chemical composition of produced RHA was observed. After combustion, RHA containing ∼93% amorphous silica and <3% unburned char was obtained. RHA primary particles presented sizes from 90 to 100 μm and a tendency for agglomeration in aqueous media. Thus, the potential of this type of reactors with respect to speed, continuity and self-sufficiency energy of the process was shown.