Evaluation of nitrogen release and the effects on the soil microbiome of organic fertilizers obtained from wet white and chromium tanned leather

The tanning industry is considered one of the most environmentally unfriendly industrial activity and 3.5-4.0 million tonnes of solid waste is generated worldwide annually, of which a significant share (up to 30%) may contain chromium (Cr). In 90% tanneries Worldwide, Cr(III) salts are used as tanning agents, and the solid waste contains up to 3% (w/w) Cr- In order to avoid this issue, wet white leathers are produced by combinations of synthetic tannins, vegetable tannins, glutaraldehyde and minerals, such as aluminium and zirconium. The present work aimed to evaluate the fertilizing potential of organic N fertilizers from wet white (OFww) and basic chromium sulfate (OFCr) tanned leathers.