A common problem in nanomaterial LCAs is the fact that detailed product system descriptions or emission inventories are
not available for the nanomaterials (Hischier and Walser, 2012). Therefore the impacts of manufacturing nano-silicon oxide were estimated by including the manufacturing of nanosized silica from silicon tetrachloride (SiCl4) in a hydrogen/oxygen flame (Wegner and Pratsinis, 2005). The amount of raw materials needed was based on the reaction stoichiometry for oxidizing the tetrachloride and producing hydrochloric acid. This served as an initial estimate
of the energy and rawmaterial impacts, but the potential emissions of SiCl4 or the nanoparticles during manufacturing were excluded. This may have resulted in an underestimation of the human health impacts, especially if occupational health would have been included. However, no standard methods for including either aspect exist for LCA (Hischier andWalser, 2012), and developing the methods would have been outside the scope of this case study. The
limitations of this exclusion are further discussed in the analysis of results.