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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.

This survey prepared and presented during the 17th UNIDO Leather Panel is a follow-up to Worldwide Study of the Leather and Leather Products Industry, which was the outcome of an exhaustive survey carried out by UNIDO in the 1970s. It is intended to assist the Organization in the formulation of future assistance programmes and in detecting areas where further study of various kinds may be useful. This report assesses the worldwide prospects of the leather and leather products industry in the coming decade. It examines the major underlying trends of recent years and how they are expected to evolve in the short to medium term. In its attempt to provide a thorough picture of the leather sector, the report covers its various aspects: the availability of raw material, the tanning industry, and the manufacture of footwear and other leather products. The basic intention is to help discern prevailing trends in global trade and to support efforts to design an effective role for organizations in the industrial development arena. The findings and forecasts published here are meant to be indicative rather than definitive and to form a basis for further surveys and studies. The need to compile this report arose out of the 16th session of the UNIDO Leather and Leather Products Industry Panel held in Brazil in May 2007. The panel recommended that UNIDO undertake a comprehensive study on the future development of the world leather and leather products industry, a study that would cover demand, technology, production, and trade. Consequently, the UNIDO study provides an analysis of the contemporary demand for leather products (footwear, leather goods, gloves, leather garments, sports goods, upholstery, etc.) vis-à-vis the availability of resources (raw hides and skins, manufacturing capacities, skilled labour, knowledge, support industries, and services). It also contains information on other important aspects of the leather industry: trade statistics, the geographic distribution of production, technology developments, physical infrastructure, environmental conditions, and social aspects involved in the production of leather.

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

 

This short paper presented during the 14th UNIDO Leather Panel in Zlin/Czech Republic reports on the general situation, issues and methodology adopted as well as practical experience in implementation of occupational safety and health standards (OSH)  at work in tanneries under UNIDO’s Regional Programme for Pollution Control in the Tanning Industry in South East Asia in late 90-ies involving .international and local experts. For a practical OSH manual see the document Occupational Safety and Health Aspects of Leather Manufacture.

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. The manual was prepared under UNIDO Regional Programme for tannery pollution control in South-East Asia.

What is future of the chrome tanning? What will be used as a tanning agent in horizont of 50 years? In this paper prepared in 1999 Mr. Frendrup analyzed possible trends and scenarios of leather manufacture. Many issues and predictions are still relevant, especially those concerning the recent EU regulations. For additional information see also IULTCS papers concerning chrome tanning http://www.iultcs.org/pdf/IUR-1_Chromiumandleatherresearch_Abalancedview...

 


 

The essential part of any tannery waste audit is assessing the efficiency of existing operations carried out during the leather manufacturing process. Typically, tannery staff have a good idea of, and comparatively accurate figures on the waste resulting from specific operations such as fleshing, splitting, trimming or chrome tanning. Only rarely, however, they have a proper overview of the entire range of waste generated. Thus, when considering various cleaner technologies or waste treatment systems, having access to a complete computation of the overall mass balance certainly makes it easier for a tanner facing arduous choices. Dialogue with environmental authorities is also simpler if such figures are readily available. This paper attempts to provide a comprehensive computation of a mass balance and the efficiency of the leather manufacturing process for a tannery, seen as a closed entity. The calculations are deliberately based on operations in a hypothetical tannery processing bovine hides and producing upper leather for shoes. With minor exceptions (batch washing instead of continuous rinsing, splitting in lime, roller coating), it follows the conventional process.

Conventional treatment of tannery effluents does not affect the TDS content (colloquially: salinity); they remain unsuitable for lifestock watering or irrigation which, especially in arid areas, represents a great loss of natural resource. This paper reports on successful irrigation trials with treated effluent from a CETP servicing a cluster of tanneries processing wet blue and crust leather into finished leather and with TDS not exceeding 5000 mg/l and chlorides not exceeding 900 mg/l. Eventually a plot of barren land was converted into a pleasant park-like area.This paper, based on the project implemented by a women-only team, provides information on saline resistant plants and assess their growth properties; and the impact that the continuous application of treated effluent had on the soil and ground water.

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.

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.

Typically only a small part of fleshings is used for manufacture of glue and animal protein while the major part is dumped as waste at landfill or disposed of along with other solid wastes. The unutilised fleshings, containing high concentration of lime and sulfide, putrefy and produce obnoxious odour. They also cause groundwater pollution, attract flies, rodents and stray dogs and thus represent a public nuisance. Due to high moisture content handling and transportation of fleshings is quite difficult. On the other hand, one tonne of wet fleshing with 85% moisture is estimated to generate 20-30 m3 of biogas. To solve the disposal problem of fleshings, one of the options considered and tested during UNIDO Regional Programme in South-East Asia was biomethanation. The results of testing at the pilot plant, the first of its kind in the region, are given in this report.

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