Anaerobic Digestion of Tannery Wastes

Anaerobic digestion is a favorable technological solution which degrades a substantial part of the organic matter contained in the sludge and tannery solid wastes, generating valuable biogas, contributing to alleviate the environmental problem, giving time to set-up more sustainable treatment and disposal routes. Digested solid waste is biologically stabilized and can be reused in agriculture.

The application of an anaerobic treatment for the break down of COD from tannery waste water is an attractive method to recover energy from tannery wastewater. Until now it was considered that the complexity of the waste water stream originating from tanneries in combination with the presence of chroming would result in the poisoning of the process in a high loaded anaerobic reactor.

When the locally available industrial wastewater treatment plant is not provided by anaerobic digester, a large scale digestion can be planned in regions accommodating a big cluster of tanneries, if there is enough waste to make the facility economically attractive. In this circumstance, an anaerobic co-digestion plant based on sludge and tanneries may be a recommendable option, which reduces the quantity of landfilled waste and recovers its energy potential. It can also incorporate any other domestic, industrial or agricultural wastes. Chrome-free digested tannery sludge also has a definite value as a fertilizer based on its nutrient content.

Waste-to-Energy in the Tannery Industry

The energy generated by anaerobic digestion or gasification of tannery wastes can be put to beneficial use, in both drying the wastes and as an energy source for the tannery’s own requirements, CHP or electricity export from the site. A large amount of the energy recovered is surplus to the energy conversion process requirements and can be reused by the tannery directly. Infact, implementation of waste-to-energy systems have the potential to make the industry self-sufficient in terms of thermal energy requirements. Waste-to-energy plant in a tannery promotes the production of electricity from decentralized renewable energy sources, apart from resolving serious environmental issues posed by leather industry wastes.

Energy Recovery from Tannery Wastes

The conventional leather tanning technology is highly polluting as it produces large amounts of organic and chemical pollutants. Wastes generated by the leather processing industries pose a major challenge to the environment. According to conservative estimates, about 600,000 tons per year of solid waste are generated worldwide by leather industry and approximately 40–50% of the hides are lost to shavings and trimmings.

The energy generated by anaerobic digestion or gasification of tannery wastes can be put to beneficial use, in both drying the wastes and as an energy source for the tannery’s own requirements, CHP or electricity export from the site. A large amount of the energy recovered is surplus to the energy conversion process requirements and can be reused by the tannery directly. Infact, implementation of waste-to-energy systems have the potential to make the industry self-sufficient in terms of thermal energy requirements. Tanneries are major energy users, and requires up to 30 kW of energy to produce a single finished hide. Thus, waste-to-energy plant in a tannery promotes the production of electricity from decentralized renewable energy sources, apart from resolving serious environmental issues posed by leather industry wastes.

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