Anaerobic treatment of tannery wastewater in the context of a circular bioeconomy for developing countries

The current economy of tanneries in developing countries is mainly linear, with certain elements of circularity as it promotes the recycling of skin/hides and direct/indirect water reuse. Solid waste management remains largely linear and is characterised by high disposal costs. However, this practice lacks sustainability and there are incidents of severe environmental pollution. The increasingly stringent legislative standards for environmental protection have created a hostile economic environment for the industry. In view of the global efforts to achieve sustainable development, the concept of a circular bioeconomy has gained significant traction in solving the tannery industry's economic and waste management challenges. The anaerobic digestion process presents a very attractive and cheaper option for the treatment of tannery wastewater while recovering reusable, recyclable and value-added products such as organic acids, bioenergy (biogas or hydrogen or biomass), biofertiliser, sulfur, metals, construction aggregate, and water. However, the application of anaerobic digestion is susceptible to inhibition by toxicants contained in tannery wastewater. This review explores the anaerobic digestion of tannery wastewater for the advancement of a bio-based circular economy. (c) 2021 Elsevier Ltd. All rights reserved.