SiSal slag valorization

Silicon (Si) and High Purity Alumina (HPA) are vital raw materials for the transition to the low carbon society; Si as a dominant photovoltaic (PV) material for solar energy applications and as an important ingredient in light-weight applications (automotive and others), while HPA is a key material in Light Emitting Diodes (LEDs) and increasingly in Lithium Ion Batteries (LIBs). Unfortunately, both Si and HPA are today produced non-sustainably; for each tonne of Si you make a lot more CO², plus harmful pollutants. Similarly, HPA is today made from ultrapure primary aluminium, having a large CO² footprint.

The project's promise

The promise of the SisAl process is to resolve this problem of non-sustainable raw materials, by replacing carbon with secondary aluminium sources (scrap, dross) as reductant for Si production from quartz (SiO²), and in parallel making an intermediate slag which is a perfect precursor for HPA processing. By introducing integrated CO² looping, the already superior low CO² footprint of the SisAl process is strengthened. Elkem (Si), SiQAl & Mytilineos (HPA), and Calef (CO² looping) will commercialise the technologies and products (Si & HPA) for the benefit of end users requiring sustainable raw materials with a minimal environmental and CO² footprint.

With the SisAl process, transformation to a low carbon circular economy and other key challenges are turned upside down into new European opportunities. Carbon leakage means moving industry to countries with less strict emission regulations, giving no positive or even negative effects on global emissions. A reversed carbon leakage would be to move industry back to Europe, and, by replacing just one traditional silicon smelter in China with a new SisAl smelter in Europe, we have estimated that 50 million Euros will be saved annually in avoided societal emission costs.


Identified commercial exploitation opportunities to be targeted in the KIC KAVA Upscaling Project “Sisal Slag Valorisation” include:

  • Technology for production of high purity alumina (HPA) from SisAl slags to be commercialised by SiQAl and Mytilineos
  • Product HPA – to be produced and commercialised by SiQAl and Mytilineos for the European market
  • Technology for production of silicon and SisAl slags (i.e. the basic patented SisAl technology) to be licensed by NTNU as commercial owner
  • Product Silicon metal (produced along with SisAl slags in the basic SisAl process) – from secondary streams to be commercialised for the global market by Elkem, Europe’s largest Silicon producer and trader
  • CO² looping technology for metallurgical applications, with an initial focus on co-production of alumina and calcia from SisAl slags, with Calef and Walter Tosto as commercialising actors

The project consortium covers the value chain from raw material provider to product user, with partners from SME´s, companies, institutes and universities.