You are here

Leather processing

In an age of plastics, metals and synthetics, leather has kept its place as a product of superior quality. As a result, tanning remains an essential economic activity. Leather processing can be done at the small-scale or large-scale level, all to varying degrees of sophistication.

The tanning industry has been subject to important challenges and changes. Foremost has been the introduction of processing technologies with less impact on the environment. As the production of finished leather is concentrated in developing countries, UNIDO, together with other partners, have provided support to enhance tanning industry practices in developing countries.

Cleaner leather production technologies remain UNIDO’s main focus in the field of leather processing. Cleaner production applications include green hide and skin processing (supply of raw material from slaughterhouses without preservation, e.g. salting), water management (use minimum volume of process water), recycling (e.g. in liming) and chromium recovery (after tanning), hair saving (to reduce dissolved solids in effluent) and application of environmentally friendly chemicals (e.g. enzymes). Special attention is also given to occupational health and safety (OHS) in tanneries.

Leather industry expert Richard Daniels In association with IULTCS, SLTC and the United Nations Industrial Development Organisation (Unido), has released an extensive guide to leather manufacturing.

The 10-part guide, which contains insight on leathermaking, was created to give aspiring leather technicians a self-training resource for the procedures used in making a wide variety of leathers. It includes 300 technical diagrams.

The study is optimised for mobile or tablet viewing and covers the raw material properties, manufacturing procedures and outcomes, and production of major leather types including:

Bovine hides
Hair sheep and goatskins
Wool-bearing sheepskins.

You can find the full guide in 10 parts (plus summary) below. The full guide was presented during the XXXVI IULTCS Congress in Ethiopia in November 2021.

Hides, skins and leather form a critical strategic sector for the economic and industrial development of Ethiopia. 

Realizing the diverse and unique issues of women employees, the EU funded  LISEC project integrated gender mainstreaming as a cross-cutting theme. The gender mainstreaming process aims to promote gender equality and women’s empowerment in selected tanneries, slaughterhouses, and hide and skin trading companies.

In order to have a deeper understanding of the gender issues that exist within the leather industry and thereby devise a strategy to address the identified concerns, UNIDO, through its LISEC project, collaborated with the gender directorates of MoTI and LIDI to conduct this gender analysis. The main
objective of the gender analysis was to gain a clear insight into the gender issues affecting the leather value chain and thus identify recommended strategic actions for more gender-responsive planning and implementation from 6 abattoirs, 6 tanneries and 2 hide and skin trading companies.

The General Objective of the study was to conduct a gender analysis to have a deeper understanding of gender issues in the leather value chain and thereby devise a strategy to address the identified issues.
Specifically, the gender analysis aimed to:
 Assess the representation, participation, and decision-making of women and men employees.
 Assess women and men stakeholders’ access to and control over resources.
 Understand cultural gender roles, norms, relations, stereotypes, prejudices affecting women and men.
 Identify the presence and justification for sex/gender-based job segregation.
 Assess practices of recruitment, retention, promotion of women and men employees.
 Assess implementation of gender-related provisions (including the revised labour law) within stakeholder companies.
 Examine the presence of conducive and family/women-friendly work environments.
 Assess migration patterns to address women’s integration in the project in the best way possible.
 Provide strategic recommendations to address challenges that women and men face, while promoting gender equality as well as women’s empowerment.

The course Introduction to Leather Testing is designed for training institutions, private companies and individuals that require understanding of both the theory and application of a wide array of standard test methods in utilize in the leather industry. The course is recommended to be used in a blend of classroom instruction using training content or self-learning along with allocation of time for hands on application in the laboratory. All courses provide opportunity for continuous professional development and lifelong learning.

The Course is divided into five modules:

M1: Fundamentals in Material Testing

M2: Basics in Leather Testing

M3: Physical Testing

M4: Fastness Testing

M5: Chemical Testing


Content was developed and prepared as a joint effort between UNIDO, FILK Freiberg Institute and Common Sense. Dr. S. Dietrich will guide you through the course. The course is offered free of charge and a certificate issued upon successful completion of the course.

The course will be available also in additional languages. The course was developed thanks to a generous support from the Government of Japan.

To register to the course, please use this link:

"SAFE Leather" must mean safe for operators and workers, as well as safe for consumers and communities. Company management must ensure that the workplace provides workers and anyone else attending the workplace with access to appropriate first aid equipment. Management must also ensure that the workers have access to an adequate number of persons who have been trained to administer first aid.

First Aid course/training should be mandatory for all emplyees. 

First Aid course Modules
Module 1: First Aid Kit - content
Module 2: First Aid Dealing with Heart Attack
Module 3: First Aid Dealing with Burns
Module 4: First Aid Dealing with Accidents Involving Chemicals
Module 5: First Aid Dealing with Contusions
Module 6: First Aid Dealing with Eye Injuries
Module 7: First Aid Dealing with Severe Bleeding
Module 8: First Aid Dealing with Eelectricity


To enroll into the course please follow the link

UNIDO Course Introduction to treatment of tannery effluents

The course, “Introduction to Treatment of Tannery Effluent” is designed for training institutions, private companies, and individuals that require an understanding of effluent treatment methods in the leather industry. The course is recommended to be used in a blended approach via classroom instruction using training content or self-learning along with an allocation of time for hands-on application in the laboratory.   There are 5 modules in this course as below:

Module 1: Load, norms, in-house treatment. This module will explain the aim of effluent treatment; pollution load and the main wastewater quality parameters; typical discharge norms.  It will also offer a general overview of the treatment of tannery effluents, segregation of streams, treatment of spent liming floats, and treatment of chrome-bearing floats
Module 2: Treatment within tannery compound. This refers to the pre-treatment for discharge into the common effluent treatment plant (CETP) collection network, and physical-mechanical (primary) treatment for discharge into municipal sewage.
Module 3: Sludge dewatering.  This module explores sludge thickeners, sludge pumps, filter press, centrifuge, belt filter press, flow-chart of physical-chemical treatment, and sludge drying beds.
Module 4: Biological (secondary) treatment.  This module looks into activated sludge, aeration devices, oxidation ditch, and the flow-chart of the biological treatment
Module 5: Occupational safety and health (OSH) in CETP, and its costing and management

Link to the course:

Safety doesn't happen by accident!

This Second Edition is a thoroughly revised and expanded version of UNIDO paper The Occupational Safety and Health Aspects of Leather Manufacture from 1999.This manual has been primarily prepared for use by tanners and tannery supervisors. It has been designed to provide guidance and ideas on how to improve the occupational safety and health standards at work in tanneries and effluent treatment plants by presenting the sources of hazards in a tannery and pointing out simple measures, in a practical and easily understandable manner, for ready implementation on-site. A special attention is given to risks associated with hydrogen sulphide gas, H2S. 

APLF webinar on safety is available here

Recommendations and preventive measures in response to COVID-19: Guidance for the industrial sector

This tool provides guidance to employers, workers and their representatives on preventive measures for a safe return to work in the context of COVID-19, conforming to well established principles and methods on occupational safety and health risk management.

There are many other useful guidelines and recommendations available.

Tanning industry is an important segment of UNIDO technical assistance in promoting sustainable development. In late 90-ies a number of studies dealing with various cleaner tanning methods, including the widely used paper The Scope for decreasing pollution load in leather processing, were prepared to support different forms of training activities (shop-floor demonstrations, pilot plants, national and regional workshops etc).

In the meantime a lot of practical experience has been gathered, some new tanning technologies developed and implemented and some new challenges have also emerged.  Since proper training is essential precondition for modern, sustainable leather processing, it is felt that a single, comprehensive paper on cleaner leather technologies, rounding up and updating earlier papers, could be of great help in training and capacity building activities.

In addition to traditional cleaner technologies topics such as pollution sources/loads, water management, hair-save liming, low- or ammonia-free deliming, chrome management, low-organic solvents finishing, solid waste management etc., this comprehensive study addresses virtually all issues relevant for performance and successful tanning operations: tannery environmental management systems (EMS/CSR), Restricted Substances Lists (RSL), energy considerations, mechanical operations, Occupational Safety and Health at workplace (OSH), Carbon Footprint (CF) and Life Cycle Analysis (LCA) which are so often the subject of extensive debates in various international fora and media.

The study also includes many tables, charts and (equipment) photos accompanying and illustrating the text.

It is envisaged that the document will serve as a basis for developing globally accessible eLearning courses on sustainable leather manufacture.

There are also other useful information and sources e.g. Tannery of the Future. The Tannery of the Future tool gives tanners an initial indication of the areas in which they need to become more sustainable, e.g. housekeeping, waste management, working conditions and wages. It also provides references to sources of more in-depth information and guidance.

The Leather Working Group (LWG) has launched an online training platform designed to educate leather manufacturers and other members of the leather supply chain on responsible operating practices.

Due to different ambient temperatures many would expect that the overall thermal energy consumption in a tannery in a hot climate zone is considerably lower than in a temperate zone. In reality it is somewhat more complex and worth comparing.

In any case, two very important factors,  (i) temperature and (ii) humidity of inlet air are often overlooked in estimation of energy required for the crust and/or leather drying.

Chamber drying in (sub)tropical zone benefits from the higher ambient (air) temperature but at the same time it is negatively affected by high relative humidity and consequently much higher volume of fresh air required. However, the fact that the energy required for water evaporation[1] does not change much with water temperature ultimately prevails over parameters such as ambient (air) temperature and air humidity. Accordingly, energy consumption for chamber drying in (sub)tropical zone with average air temperature of 30oC and relative humidity  in the span of 50-90 % is only about 5 % less than in the temperate zone.

However, if the solar energy is used to support water heating, the conditions in the tropic zone are substantially more favourable, due to two factors:

efficiency factor (depends on the temperature difference of the final vs. inlet water temperature)

The insolation in the temperate zone (Europe) is approx. 1500 kWh/m2/y (4.1 kWh/m2/d), and in the tropical zone (South India) approx. 2200 kWh/m2/y (6.0 kWh/m2/d), so that the factor of proportionality is 1.5. Since the efficiency ratio case can be estimated as 1.05 it means that the solar based production of thermal energy in a hot climate country is about 1.6 times more favourable than in temperate climate.

 The (latent) heat of vaporization is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. The enthalpy of vaporization is a function of the pressure at which that transformation takes place.


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.