Use of leather industry residues as nitrogen sources for elephantgrass

Large amounts of solid wastes are produced in tanneries, which use chromium (711) to obtain wet blue leather hides. The solid residues (leather scraps and strips) contain around 3% chromium(III), which represent a serious environmental problem and, presently, have no adequate destination. The leather waste after chromium extraction (collagen) was used as a nitrogen source for elephantgrass- Pennisetum purpureum Schum cv. Napier. Four doses of collagen (4, 8, 16, and 32 t ha(-1)) and three additional treatments (control; mineral fertilizer N; and wet blue leather residue without Cr extraction) were used. Collagen as alternative nitrogen source has a positive effect on elephantgrass growth at rates up to 16 t ha-1. Little N became available to elephantgrass plants after application of wet blue leather residues. These results show that the phosphoric acid extraction of chromium is necessary if leather waste is to be used as a nitrogen source in agriculture. The application of collagen supplied the N need of elephantgrass plants, similarly to mineral N fertilization.