This paper, a thoroughly revised and expanded version of UNIDO’s paper ‘The Framework for Sustainable Leather Manufacture’ from 2014, is primarily prepared to reflect recent developments that have taken place in defining and computing the leather carbon footprint (CF), about the presence of restricted substances in leather, and to expand the texts dealing with subjects such as sustainability, vegetable tanning, the future of leather, and the promotion of leather as a noble, unique and sustainable material.

On the whole, the general intention of the paper is to present and promote the concept of leather as a sustainable and safe material. To be classified as safe, it has to be safe for operators (occupational safety and health at the workplace, OSH), communities (all emissions treated and safe) and users. Finally, a tanner (producer) also has to design leather in a way that will facilitate its handling and disposal at the end of life.

Sustainability and environmental footprints are some of the main challenges of any manufacturing process and leather is no exception. The leather industry is aware of this challenge, and the reduction of its environmental footprint is one main topics at conferences and congresses. Indeed, in the past few years there has been a lot of development in this area. Contrary to popular perception, the leather industry is continuously innovating by developing new methods and auxiliaries to achieve desired goals, and meet customers’ quality and environmental requirements. There are many new technologies and ideas from industry suppliers and service providers.

Not only does the leather industry process renewable material (hides and skins), chemical companies and suppliers have also developed many chemicals based on renewable resources and various bio-polymers. Machine and equipment suppliers have improved energy efficiency and in some regions the implementation of closed-loop systems for water reuse has almost been achieved. These advancements have resulted in the preparation of the second edition of the ‘Framework for Sustainable Leather Manufacture’.

Cleaner leather technologies

There is no shortage of papers dealing with specific aspects of pollution control, including cleaner technologies in leather manufacturing, such as operations in the beamhouse, (chrome) tanning or finishing. On the other hand, there is much less widely accessible information that provides a comprehensive overview covering the scope of preventing and reducing polluting emissions throughout the entire leather-making process.

The evolution that took place during the past few decades is also to be recognised; concepts such as Best Available Technology, Not Entailing Excessive Costs (BATNEC) from the early 1980s, and Cheapest Available Technology Narrowly Avoiding Prosecution (CATNAP) some 20 years later, are by now long abandoned and forgotten. Documents prepared by the Environmental Commission (IUE) of the International Union of Leather Chemists and Technologists Associations and the Best Available Techniques Reference Document (BREF) prepared in the EU (both updated from time to time) are globally referred to for guidance on what can be considered a cleaner technology method.

However, while being very useful, they don’t coincide with the profiles and needs of a large segment of tanners, especially in developing countries. BREF is written in a specific format for conditions prevailing in the EU, whereas the IUE set of documents might not be detailed enough for practical purposes. In the past few decades, under various projects of technical assistance and under the auspices of its well-established Leather and Leather Products Industry Panel, UNIDO has prepared a number of studies dealing with various cleaner tanning methods such as mass balance; desalting of raw hides and skins; hair-save unhairing; chrome balance and chrome management; hair-save liming; and detection and avoidance of hexavalent chromium. Now it is believed to be the time to prepare a single, comprehensive study on cleaner leather technologies, round up and update earlier papers, and supplement the IUE and BREF documents.

In this paper, an attempt has been made not only to revisit the traditional ‘standing’ issues (water-saving, deliming, chrome management) but also to present a fresh, neutral assessment of some cleaner methods based on years of practical experience. In conformity with new trends (and environmental and legislative pressures), both wet and dry finishings are discussed in more detail than before. Energy consumption, traditionally sidetracked, is also now looked at more closely.

Serious scientific papers and media headlines about greenhouse effects and global warming, and the anticipated public pressures on the leather industry – including current discussions in various leather fora possibly triggered by the UNIDO Leather Panel meeting in September 2012 in Shanghai – resulted in a mosaic of information and views under the ‘Life Cycle Analysis (LCA) – Carbon Footprint’ chapter. Indeed, throughout the paper the approach is to present information about experiences gathered and options available to date, and to point out their advantages and disadvantages without strong preference, and certainly not imposing a particular method. After all, there is no general consensus, even about the right terminology or the best available technology. In this context, it is useful to remember that there is no unified approach on what is to be classified as a hazardous substance.

Possibly oversimplifying the matter, it could be said about the EU approach that strong suspicion about potential harmful effects suffices, whereas in the US the negative impact has to be proved. Finally, it can’t be overemphasised that a significant decrease of polluting loads can be achieved by strict process monitoring and control, and minor modifications of the traditional, conventional technologies, without high investments or the use of expensive proprietary speciality chemicals.

Predicted growth of the luxury market in Asia in 2019, excluding Hong Kong and Macau.
Bain & Company

Measuring environmental impact

Restoring and maintaining the balance between natural resources, and consumption and population growth, is one of the key elements. Generally, it is taken for granted that human impact is measurable. In reality, there is no universally accepted sustainability measuring system or unit. Among those proposed are the Sustainability Development Indicator (SDI), the Human Development Index (HDI), the Environmental Sustainability Index (ESI) and the Environmental Performance Index (EPI). Also important is the IPAT equation: Human Impact (I) = Population (P) x Affluence (A) x Technology (T) where A = consumption per capita and T = environmental impact per unit of consumption.

“Pollution prevention and the persistent promotion of cleaner leather processing obviously remain of paramount importance.”

€260 billion
Value in 2018 of the global personal luxury goods market, which grew by 6%.
Bain & Company

Possibly the best is the sustainability approach proposed in the UN Brundtland Commission Report from 1987 stating that sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs. The Daly Rules approach suggests the following criteria of sustainability:

  • Renewable resources must be used no faster than the rate at which they regenerate.
  • Non-renewable resources must be used no faster than renewable substitutes can be put into place.
  • Pollution and wastes must be emitted no faster than natural systems can absorb them, recycle them, or render them harmless.

Some suggest that sustainability indicators should be holistic, measuring sufficiency of well-being for all, sustainability of natural resources and efficiency of converting resources to universal well-being; they believe complex systems require multiple viewpoints to adequately express the needs of all in the system.

In that context, sustainability also implies maintaining adaptive capability, and development means maintaining opportunity so that sustainable development corresponds to fostering adaptive capabilities and creating opportunities. In essence, sustainability calls for renewable raw materials, recycling and waste reduction.

The tanning sector must adhere to these principles at every stage, especially as its perception has been bad; its status in virtually all cultures around the world is among the lowest. Even today, the malodors from poorly run tanneries overshadow the fact that, for example, the production of 1m2 of blue jeans requires about 10 times more water than for 1m2 of leather.

With most consumers, the perception of leather as a natural material is invaluable, and it should be preserved and increasingly associated with sustainability, which is why the leather industry itself should insist on very strict sustainability criteria.

While the shortage of chemicals needed for leather processing is very unlikely, the emphasis is on much higher uptake than is the case now and, in particular, the need to be fully degradable into non-hazardous components and without any adverse effect on organisms in the water recipient. However, two elements may be critical for long-term sustainability of leather: the availability of both fresh water and sewage systems able to accept the (treated) tannery effluent, and salt or the salinity of tannery effluents.

Prioritise sustainability

It could be argued that energy should be included as well due to the CF load attached to leather if the tanning industry does not switch to energy from renewable sources. The spread of cleaner technologies and processes is neither spontaneous nor extensive. For all the claims about favourable cost-benefit ratios and environmental benefits to be derived from many of these technologies, tanners are not quick in adopting them, be it due to inertia, higher costs or some other limitation.

Contrary to some misperceptions, extensive investigations have shown that chrome tanning remains the most environmentally efficient tanning method, whereas vegetable and synthetic tanning agents are preferred when specific leather properties are required, like in the case of sole and saddlery leathers (vegetable) and automotive leathers, which need dimensional stability (synthetic tannage). In view of ever-increasing legal, local and global social pressures, no tanner can afford to not be familiar with the main issues and principles of environmental protection pertaining to tannery operations. Pollution prevention and the persistent promotion of cleaner leather processing, which ultimately leads to lower treatment costs, obviously remain of paramount importance.

In recent years there has been a striking change in the importance attached to environmental aspects and sustainability by virtually all reputable suppliers of speciality chemicals to the tanning industry. Most of the leading suppliers are members of the Zero Discharge of Hazardous Chemicals foundation, which promotes the view that the industry must not produce more waste and emissions than can be degraded by the environment within the same period of time, commits to producing retanning materials that contain little or no salt, and promotes processes designed to reduce the weight of leather, and increase its service life and a leather recycling process.

While legislative and marketing aspects might be the key drivers behind this, it is beyond any doubt that suppliers contribute to greener production and public perception of the industry. The majority of companies understand the importance of sustainability, yet do not fully recognise how to incorporate it into daily business life.

Full integration of sustainability within a business requires considerable time and money, and, inevitably, there is always a question of what the financial benefits for the tannery are.

Incorporating sustainability and innovation in a tannery reframes a company’s identity. Tanneries that are continuously building sustainability initiatives create quantifiable goals to be met over defined time periods, incentivise employees to innovate, receive support from management and regularly bring in third-party auditors to review progress. Sustainability is not usually deliverable in short-term financial results, and change occurs over the medium to long term. In any case, customers want increased performance from their leather products but are also starting to analyse products’ reputations for sustainability.