Environmental concerns, limited resources, tighter legislation, increased awareness among customers, and social, cultural and economic factors are forcing changes in the leather industry. Sustainability is now an integral part of the modern leather supply chain. Although sustainability has become a buzzword recently, the concept of sustainability perhaps emerged over 135 years ago.

For this article, literatures were reviewed from the early 1900s up to the 21st century to ascertain the sustainability concept within the industry for various time periods. However, the literature reviews were all written in English; therefore, some international differences may not be covered.

In the early 1900s, most published articles were based on analysis, experimental trials or theory behind existing manufacturing practices, oriented towards giving greater scientific underpinning in understanding the process functionality and mechanisms.

Anthrax appeared to be one major issue. A double-bath chromium system was in common use but a single-bath chromium system had also been introduced.

Concern for public health due to tannery pollution was raised during this period. Conditions of English rivers in the large manufacturing areas were described as extremely bad, due to the presence of solid waste containing organic matter resulting in high oxygen demand. Solid waste also remained an issue for the modern leather industry. Arsenic was also still being used in unhairing. However, the leather industry had already started to address issues of pollution.

Law of the land

Legislation was published in order to protect the environment and public. For example, the Public Health Act 1875 and River Pollution Prevention Act 1876 in the UK prohibited discharging of ‘solid matter’ to streams or any interference of flow, and ‘sewage’ and ‘harmful, toxic or polluting’ liquid to rivers. The 1899 Navigation Act was also introduced to prevent the deposition of waste to navigable waters (except for liquid from streets and sewers).

The passing of tannery effluents through a bed of coke appeared to be a standard method of treatment before discharging to the rivers. The discharge of effluent to public sewers was also possible; however, admission was dependent on the local authority. Various effluent treatment options such as precipitation of lime and tanning liquor, biological treatment of sludge using bacteria and purification of liquid tannery waste by oxidation were investigated. The toxic effect of hexavalent chromium was also apparent and the development of acute sores, due to contact of skin wounds with dichromate had been recorded. The sores were persistent if the handling of dichromate solutions was not stopped. Stomach and kidney diseases were also linked to chromium-VI poisoning.

The following suggestions were given to the workforce in order to avoid chromium poisoning:

  • make all workmen aware of the toxic effect of chromium and transmission routes
  • limited contact time
  • apply sodium bisulphite solutions
  • avoid direct contact whenever possible (use of gloves; application of petroleum jelly or vegetable oils)
  • avoid eating and drinking on the premises
  • avoid dust formation while working with chromium powder 
  • have regular urine tests performed by a physician.

Thoughts were also given to reducing raw material wastage by ensuring raw material quality. This could be obtained by following good animal husbandry, flaying and preservation practices, and process efficiency. Conversion of waste to energy was also mentioned, which is now being recognised as an option to convert waste to a by-product.

Other pollutants to consider

Elsewhere, environmental pollution due to gas lighting was also reported, which may have contributed towards the deterioration of vegetable-tanned leather. 

Around 1905, the focus on pollution issues within the leather industry increased. Many leather textbooks published during this period contained a chapter on effluent treatment. Effluent from the leather industry was described as “Large in volume, extremely putrescible and difficult to treat in a satisfactory and economical manner,” in The Chemistry and Technology of Leather, Volume III.

Approximately 85–95% of the total waste was generated from the beamhouse processing. According to the literature, the double-bath chromium tanning system was still in use but application was limited to the manufacture of glazed/glacé kid leather from goatskins. The single-bath chromium system was popular due to the increased efficiency of chromium uptake, lower labour and material costs, and no yellowing effect on leather in comparison with the double-bath chromium tanning system.

The options that were suggested to deal with the effluent were as follows: changes of process, chemical substitutions, improved housekeeping, personnel training, monitoring of effluent discharge, recycling, reuse and recovery of usable materials from the effluents before treatments and final disposal. All these suggestions are still very relevant to modern leather-making.

Progress over time

By the late 20th century, chromium chemistry was well understood, not only in terms of understanding the hazardous impact of hexavalent chromium and issues with disposal of chromium-tanned leather waste, but also the understanding of options to control hexavalent chromium formation. Single-bath chromium-tanning systems completely replaced the double-bath chromium-tanning system.

Beamhouse still contributed 75–85% of the pollution load. Pollution potential included COD (chemical oxygen demand), BOD, solids, oil and grease, nitrogen (TKN and ammonia), sulphide, chromium and pH levels. Elsewhere, changes in finishing technology away from organic solvents to water were taking place.

Effluent concern was considerably increased. The first meeting of the IULTCS (International Union of Leather Technologists and Chemists Societies) commission was held in the Netherlands in September 1970. Guidelines on waste treatment and disposal options were also published. The Waste Framework Directive (1975/442/EEC; 1991/156/EEC) introduced the ‘polluter pays’ and ‘the waste hierarchy’ concepts.

During this period, pressure groups such as ‘environmentalists’ and ‘consumerists’ were observed. The influence of pressure groups is highly noticeable in the current leather industry. Along with environmentalists and consumerists, there are also animal rights activists that considerably influence the international leather industry.

Certification and authentication have now also become very important. As the leather industry moved to the 21st century, just treating effluent was not considered satisfactory. Social and economic issues have been given a similar level of importance to the environment. Corporate social responsibility (CSR) has become a key aspect for many organisations. The best CSR practices are now recognised and celebrated via the ‘Tannery of the Year’ award.

REACH (registration, evaluation, authorisation and restriction of chemicals) regulations have also been introduced. The revised Waste Framework Directive 2008/98/EC was published and introduced the waste hierarchy model, which divides into five distinct levels (see figure, left). The footprint concept was also introduced, adopted and expanded. The leather industry not only recognised its water and carbon footprint, but started to extend to monitor its ‘tox footprint’, which includes restricted and harmful substances, and a resource footprint.

The technology has progressed to a level that the leather industry is able to manage effluent effectively. Although salt and solid waste is still a concern, they are manageable. However, end-of-life product disposal has become an issue. A large number of consumer goods, including foods, clothes, and shoes are disposed of, which predominantly ends up in landfill. The estimated global footwear consumption in 2010 was 20 billion a year. In 2003, European shoe consumption was 4.5 pairs per person. Currently, there are no effective or efficient ways to avoid this disposal, and therefore needs ongoing research. Finally, leather manufacturers in the future may also become liable for end-of-life leather waste.

References available on request.