High-quality biogenic silica from agricultural residues

The project deals with the combined energetic and material utilization of Si-rich agricultural residues such as rice husk or oat husk comprising the optimization of the different process steps with regard to technical and efficiency aspects, sustainability and cost effectiveness. For this paper, current results on the thermo-chemical conversion of pre-treated loose rice husk are presented using ÖKOTHERM® furnaces up to 88 kW. Aspects of the fuel and ash handling, gaseous and particulate emissions, emission control measures as well as properties of the final silica rich product are covered. It is possible to establish a stable combustion process over hours with adequate fuel and ash handling and low gaseous emissions. Particulate emissions can be efficiently reduced using tissue filter systems. The burn-off of the fuel has to be further improved. So far, the specific surface area ofthe biogenic silica is about 150 – 200 m 2 /g and the produced silica ashes are amorphous with sometimes minor crystalline fractions.