Solar power is a clean alternative energy; however, the silicon sludge will be generated from the silicon crystal slicing process inevitably. Professor Wei-Sheng Chen from the Department of Resources Engineering in National Cheng Kung University (NCKU), Tainan, Taiwan, has developed a technique to recover reusable silicon and silicon carbide from waste sludge.

By transforming silicon sludge to usable raw material for steel industry, this newly introduced recycling technique not only answers the question of industrial waste disposal, but also leads to a resources circulation and cheaper raw materials for steel industrial, according to Chen.

The recycling-based technique is patented in Taiwan, and its technology transfer was completed at the end of last year, so the technique is now being applied in the iron and steel industry.

As conventional solid waste treatment is extremely costly and technically complex, it has been abandoned by the majority of waste disposal and treatment companies.

However, during the past three years, NCKU has made great breakthroughs in the separation and purification technologies.

Now, Silicon and silicon carbide can be effectively sorted out and the products can be used as raw materials by the ceramics, glass, refractory and iron and steel industries.

According to Chen, Taiwan’s solar power industry is flourishing, which results in the production of plenty of industrial waste; this in turn means that there is a great supply of silicon and silicon sludge through the utilization of the technique.

He adds that, though the previously mentioned industries may all use silicon and silicon carbide as raw materials, because the overall amount is limited, the best destination should be the iron and steel industry, which has a huge demand.

Chen also said that because silicon-based solar panels contain a variety of other materials, its purification and extraction technique requires a higher order.

Additionally, the semiconductor fab manufacturing process will also produce large amounts of silicon sludge, because it does not contaminate with grinding media, its recycling procedure is relatively simpler.

Chen said, once the silicon resource recycling model is fully established in Taiwan, not only would it help silicon resource conservation and environmental benefits, both solar and semiconductor fab manufacturing industries need no longer worry about the disposal of silicon sludge.