An important byproduct of silicon metal production is silica fume (mikrosilica). This material is separated from the furnace off gas in large filter units. It is an important raw material for refractory materials, concrete or fiber cement.
Due to the refining process for silicon a so called secondary silicon is produced. It consist mainly of silicates, alumina and lime with a high amount of elementary silicon. It can be used in steel industry as an deoxidizing agent.