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Cleaner Technologies

  • UNIDO Solar Water Heating - Ayuub Brothers, Hazaribagh, Dhaka, Bangladesh
  • UNIDO Solar Water Heating
  • UNIDO leather Screen - Hair saving liming technology

Cleaner production is an efficient method of preventing or minimizing pollution caused by industrial activities. UNIDO continues to place an emphasis on the introduction of cleaner leather processing technology in developing countries. The primary task of all cleaner technologies is to reduce the amount pollution emissions; and where possible change the nature of pollution emissions to reduce the pressure and costs of end-of-pipe treatment. The expected results primarily include:

  • Lower water consumption – better preservation of rapidly diminishing water resources.
  • Lower total dissolved solids (TDS) content (including salinity) – lower risk of affecting the usability of the receiving water bodies for irrigation and livestock watering.
  • Avoidance of use in processing and/or presence in leather of substances from the Restricted Substances Lists (RSL) promulgated by national or regional legislation, leading (multinational) brands and/or ecolabel due to their proven negative impact on human health and eco-systems.               
  • Proportionally higher volume of solid wastes suitable for processing into saleable by-products.
  • Lower levels of BOD, COD and Nitrogen; their respective contents in conformity with local and widely prevailing legislative norms.
  • Low level of chromium in (C)ETP sludge – the scope for land application and/or composting.
  • Lower hazardous and/or unpleasant air emissions.
  • Appropriate occupational health and safety (OSH) standards – better work conditions, fewer accidents.

With increasing pressure from the pollution control authorities, tanners in many countries of South East Asia region are faced with the urgent task of utilization or safe disposal of solid wastes from tanneries, particularly fleshings. Likewise, sludge generated by tannery effluent treatment plants has to be either put to use or safely disposed. These two issues were highlighted by the industry and government representatives of countries participating in the Regional programme for South-East Asia.

The report contains details of the large scale pilot project implemented under Programme, characteristics of fleshings and sludge charged to the digestors, volume of gas generated vis-à-vis projection, coping with the hydrogen sulphide gas (H2S) and the many valuable lessons learnt. Details of the problems encountered – both process-related and mechanical – have been narrated. At the time of the report preparation (2002) it was the only operational plant of its kind in the world

Due to climatic conditions the scope for green processing is limited in many countries, sodium chloride is widely used to preserve raw hides and skins. It contributes to a high volume of total dissolved solids (TDS) in the soak waste liquor. No commercially viable technology for treating effluent has been developed to date. A large amount of the salt sticking to the hide and skin surface can be removed by shaking the hides mechanically or manually.
Within the framework of the UNIDO regional programme for pollution control in the tanning industry in South-East Asia, a pilot demonstration unit was set up to demonstrate different options for

(a) desalting hides and skins prior to soaking and

(b) reusing dusted salt in the pickling operation after purifying the salt recovered.

This report covers the demonstrations carried out during the period January 1997 to February 2001 of desalting of salted raw stock and use of the recovered salt in pickling.

The Technology package "A System for Recovery and Reuse of Chromium From Spent Tanning Liquor Using Magnesium Oxide and Sulphuric Acid" provides practical overview of the chrome recovery process including equipment specification.

This study is primarily focused on the pollution load discharged in effluents and the scope for decreasing that load. In addition to knowing how to produce and sell high quality leather, tanners must also be familiar with techniques for decreasing the pollution load discharged in effluents from individual processing operations. The study aims at heightening tanners’ awareness of those techniques. It calculates the decreases possible in a well-managed tannery processing bovine hides into chrome tanned leathers and describes how pollution load can be reduced by introducing advanced technologies based on low-waste processing methods that have been proven on an industrial scale will be taken into account. The study does not consider industrially unproven and purely experimental methods.

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.

Chrome tanning is the most common type of tanning in the world. Chrome tanned leathers are characterised by top handling quality, high hydro-thermal stability, user-specific properties and versatile applicability. Waste chrome from leather manufacturing, however, poses a significant disposal problem. Throughout the world, chrome discharge from tanneries is subject to strict regulations. That notwithstanding, chrome is a component that has to be strictly monitored. The environmental impact of chrome discharged from tanneries has been a subject of extensive scientific and technical dispute. Although the legislative limits on the disposal of solid chrome-containing waste have been relaxed in some countries, liquid emissions remain strictly regulated throughout the world. Given the close link between chrome tanning and the environmental impact of leather manufacturing, chrome management is of primary importance in tanning operations. This paper provides information on chrome management and those techniques most frequently used to reduce the amount of chrome in tannery wastewater. By providing information and citing practical experience, the paper aims at contributing to sustainable development of leather manufacture without avoidable harm to environment.

Case Study prepared for the Conference on Ecologically Sustainable Industrial Development (ESID), Copenhagen, Denmark, 14 - 18 October 1991.

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