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Solid Wastes

The leather processing industry produces large amounts of solid organic wastes in the form of un-tanned  (trimmings , fleshings, splits) and tanned (trimmings, splits and shavings) waste from raw hides and skins, semi-provessed leather, as well as sludge as a result of wastewater treatment. If these solid wastes are not properly treated and disposed of, they can cause environmental damage to soil and groundwater as well as emissions of odour and poisonous greenhouse gases into the atmosphere.

 This website includes various options for different fractions[icm1]  of solid wastes generated by the leather industry. These options have been successfully implemented by UNIDO. Results and lessons learned are included in this part of the Leather Panel website.

This paper attempts to discuss the main, predominantly technical, issues with regard to benchmarking; it is intended to assist those who are willing to admit to the fact that despite all explanations and definitions available, they are not quite sure what it is all about and whether and how it could be applied in the tanning industry. The paper outlines "cock-pit" check lists for ten areas - components: 1. Tannery location, infrastructure 2. Production parameters 3. Cleaner technologies 4. Energy management and consumption 5. Quality assurance, reprocessing, delivery time, failures 6. Product development, strategies 7. Occupational safety and health at work, maintenance 8. Effluent treatment, solid waste, air emissions 9. Financial indicators 10. Human resources and staff welfare, CSR. Some typical production parameters are also provided.

The Tannery of the Future Foundation developed self-assesment tool for tanneries


Presented publications documents UNIDO's involvement in promoting Eco-Labelling in the leather industry. Life-cycle assessments or the evaluation of the potential environmental impact of a product system from cradle to grave are fundamental features of some ecolabelling schemes and environmental management systems. Nowadays rhe environmental auditing protocol and reporting mechanism developed and maintained by the Leather Working Group aims to tackle important topical issues, and reflect improvements or changes of technology within the sector.

Th report provides an overview of publications, standards and references for the calculation of the Product Carbon Footprint (PCF) of the product Finished Leather together with recommendations for harmonization and the main elements needed to define system boundaries. The inherent complexity and inadequate exactness of carbon footprint analyses contrasts with the need to communicate the results in a simple, clear and unambiguous way. The report was prepared for and presented by Mr. F. Brugnoli  in the 18th  UNIDO Leather Panel in Shanghai/China September/2012

International concern has increased over the years on Climate Change. The ten hottest years on record have all occurred since 1998. Out of the last 21 years 18 are among the 20 warmest years since 1880. Data and findings add weight to the common conclusion that the clear long-term trend is one of global warming. Most of the observed increase in global average temperature since the mid - 20th century is very likely due to the observed rise in anthropogenic greenhouse gas concentrations. Among these, particular attention is paid on CO2 (carbon dioxide). Latest estimates show that global CO2 emissions increased to 30,600 million tonnes in 2010. Industry and manufacturing contribute for 19% of all Greenhouse Gas Emissions. Interest has been developed in estimating the total amount of GHG produced during the various stages in the life cycle of products. The outcome of these calculations, are referred to as Product Carbon Footprints (PCFs). Currently, there is no single methodology and no agreement has been reached internationally on Leather PCF calculation methods.

The Regulation of the European Union (EU) on Registration, Evaluation, Authorisation and Restriction of Chemicals, REACH entered into force on 1st June 2007. Its proclaimed aims were to ensure a higher level of protection of human health and the environment as well as free movement of substances, on their own, in preparations and in articles, while enhancing competitiveness and innovation.

This Regulation should also promote the development of alternative methods for the assessment of hazards of substances. REACH was also expected to streamline and improve the former legislative framework on chemicals in order to improve the protection of human health and the environment from the risks that can be posed by chemicals, especially by those listed as Substances of Very High Concern (SVHC) The purpose of this desk study was to give some background information and practical advice to the leather industry so as to maintain or establish business in the EU market.


Utilization and/or safe disposal of sludges generated in the course of effluent treatment still represents a great challenge; worldwide many methods have been explored and proposed. This report describes the attempt made under UNIDO Regional Programme in South-East Asia to test another path. The idea was to convert the hazardous tannery sludge  into an inert, physically stable mass, with very low leachability and sufficient strength to allow making building materials like nonfired bricks for fencing or for landfilling or land reclamation. Solidification  (cementation) was achieved by mixing the sludge with various materials to form a solid product hoping that immobilisation/chemical stabilisation) will also be achieved.

UNIDO on-line learning How to deal with hydrogen sulphide gas

Confronted with increasing legal and social pressures, no tanner can afford the luxury of not being familiar with the main issues and principles of occupational, safety and health protection pertaining to tannery operations.

Hydrogen sulphide gas present in tanneries and effluent treatment plants has proven fatal to workers exposed to it many times.

It is therefore necessary that the owners and managers of tanneries and effluent treatment plants are fully aware of the dangers posed by this poisonous gas and take all preventive and precautionary measures to protect the workforce from exposure to this gas. In the event of accidental exposure of a worker, they should know how to deal with the situation.

The lessons that follow are to help tanners, tannery managers and operators to acquaint themselves with the basic principles How to deal with hydrogen sulphide gas.

The on-line course developed by UNIDO including test provides an opportunity for the proper training within tanneries related to danger associated with hydrogen sulphide gas. After finishing the test with minimum score 80%, participants will receive the certificate and will be able to download it.

How to enrol into the UNIDO on-line course “ How to deal with hydrogen sulphide gas”?

Follow a link:

Enrolment key: H2Safety


It is hoped that the certificate will be accepted also by Occupational Safety and Health Authorities as a proof that staff was properly trained.

Processing of one tonne of raw hides results in approximately 100 kg of wetblue shavings, the utilization and/or safe disposal of which is globally a serious challenge. Currently a part of the chrome shavings is used in the manufacture of leather board by combining with shavings of vegetable tanned leather. There have been also other methods tested and used to convert shavings into sellable product, e.g. application in paper, wood and other industries.

The method described in this report is enzymatic digestion.

Conversion of chrome shavings into usable products employing the technique of enzymatic digestion as developed in the United States of America and already implemented in a 3 tonnes/day commercial plant in the Czech Republic. Three products, namely, gelatable protein, protein hydrolyzate and filter cake are obtained from enzymatic digestion of chrome shavings. While the products obtained find use in construction and plywood industry and also as nitrogenous fertilizer, the chrome-containing filter cake can be used as a reducing agent in the preparation of basic chromium sulphate.

The method was successfully demonstrated at pilot scale in India using wooden tanning drums.

Historically, for various reasons, tanneries have been generally found in clusters in many countries. In several countries that still possess a strong tanning industry, the industry has either been able to deal collectively with the environmental challenges by means of common waste treatment facilities in existing clusters (e.g. India, Italy, Pakistan) or is in the process of relocation.

Within almost all projects of tannery relocation there are common reasons and the main problems faced by the industry at the current location are:

With no infrastructure for treatment of solid or liquid waste generated by tanneries, a very unhygienic atmosphere has been created in the entire locality due to discharge/disposal of untreated solid and liquid wastes.

Due to extreme limitations of space, even tanneries wanting to modernize and become more efficient in terms of production and environment management are unable to do so. The present location, in this manner, has become a serious constraint for the growth of the industry.

Downstream industries such as footwear, leather garment and leather goods, depend on the tanning industry for supply of quality leather. The existing limitations have put a limit to the growth of leather products industries.

Relocation of the tanneries to a more spacious location with appropriate infrastructure for efficient and cost effective treatment of solid and liquid wastes has thus become a prerequisite for survival and growth of the leather industry in such cases.

Generally 35-60% of the total solids in tannery sludge is organic matter. A number of solutions for utilization and/or safe disposal of tannery sludge have been proposed, practiced, tested and applied at pilot and industrial scale. Composting is one of these options and this report describes results of tests and application of sludge composting on low, non-mechanized scale together with its utilization as soil conditioner for nonedible plants.

Utilization or safe disposal of sludge generated by tannery effluent treatment plants poses a challenge worldwide; landfill disposal should be considered only in case when no other viable option is possible.  Unfortunately, in some areas and/or developing countries properly designed and constructed landfills are not available either.
With the technical assistance of UNIDO, CETP-Ranitec in Ranipet, Tamil Nadu, India, established a low cost pilot scale demonstration landfill in October 1997, the first of its kind in the region. The report describes requirements for a safe landfill disposal and practical recommendations for replication.