“…Some studies have proposed the agricultural use of composted tannery sludge as an alternative treatment method like that of other similar solid waste (Singh et al, 2015;Singh, Singh, Ibrahim, & Hashim, 2011;Silva et al, 2010). Previous studies have shown that the use of composted tannery sludge has improved the soil fertility and crop yield (Miranda, Nunes, Oliveira, Melo, & Araújo, 2014;Araújo, Lima, Santos, & Schmidt, 2016). On the other hand, the application of composted tannery sludge has been reported to increase the Cr concentrations in the soil (Santos, Araújo, Nunes, Oliveira, & Melo, 2014), which could limit its use for agricultural purposes, since this element can be easily absorbed by the plants (Gondek, 2008).…”