Treatment and valorization of leather industry solid wastes: A review

The state-of-the art of the different approaches available in the scientific literature for the treatment and valorization of solid wastes generated from the leather industry has been presented in this review. Tanning processes generate significant volumes of by-products and waste materials and, because of that, tanneries can cause serious negative environment impacts. The advancement of laws protecting the environment have prompted industrialists, environmentalists and scientists to look for the decontamination of wastes and to transform tannery solid waste materials to valuable co-products useful to be recycled or employed in other industries. Examples of the preparation of organic fertilizers, production of biomaterials, gelatins or collagens with multiple applications and production of energy by biomethanization have been proposed as solutions for untanned wastes. Several applications and treatments were proposed for tanned wastes, such as preparation of materials with multiple uses, recovery of proteins and chromium and their valorization, incineration, use of the solid tannery wastes as sorbents or adsorbents for removal of organic pollutants from wastewaters, etc. On the other hand, tannery sludges can be treated and recycled in tanning process or used for various applications in other industries. This paper has been focused on solutions and answers for researchers and concerned industry leaders who are seeking to improve the environmental quality of their activities in the tannery field.