Agricultural waste being the major solid waste in the environment, the study has explored and identified the presence of minerals especially silica in the agricultural waste like sugarcane bagasse ash and rice husk ash by carbonization on combustion at different thermal conditions and biodegradation. Presence of silica in the ash samples has been well characterized by the XRD, FT-IR, EDX, SEM and N-2 sorption techniques. Presence of crystal phases of silica like quartz and cristoballite is well indexed by the X-ray diffraction peaks that appeared at 2 theta = 27, 40 and 60 which is further confirmed by the peaks at 1100, 820 and 620 cm(-1) of FT-IR. The elemental composition of the silica in ash is determined by EDX analysis. The exothermic reaction and the mass loss observed in the TG/DTG at the transient temperature of 840-850 A degrees C has confirmed the presence of the alpha-quartz. SEM micrograph has also supported the presence of silica and has revealed the various crystal shapes that were present in the sugarcane and husk ash. The study has clearly revealed that the silica content has increased with the increase in temperature and refinement of the combustion condition to a maximum of 18.7-52 % and on biodegradation to about 48.3-92.4 %.