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Solid Wastes

The leather processing industry produces large amounts of solid organic wastes in the form of un-tanned  (trimmings , fleshings, splits) and tanned (trimmings, splits and shavings) waste from raw hides and skins, semi-provessed leather, as well as sludge as a result of wastewater treatment. If these solid wastes are not properly treated and disposed of, they can cause environmental damage to soil and groundwater as well as emissions of odour and poisonous greenhouse gases into the atmosphere.

 This website includes various options for different fractions[icm1]  of solid wastes generated by the leather industry. These options have been successfully implemented by UNIDO. Results and lessons learned are included in this part of the Leather Panel website.

Safe Landfill for Disposal of Sludge from Tannery Effluent Treatment Plants

Utilization or safe disposal of sludge generated by tannery effluent treatment plants poses a challenge worldwide; landfill disposal should be considered only in case when no other viable option is possible.  Unfortunately, in some areas and/or developing countries properly designed and constructed landfills are not available either.
With the technical assistance of UNIDO, CETP-Ranitec in Ranipet, Tamil Nadu, India, established a low cost pilot scale demonstration landfill in October 1997, the first of its kind in the region. The report describes requirements for a safe landfill disposal and practical recommendations for replication.

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PDF icon safe_landfill_for_disposal_of_sludge_from_tannery_etps.pdf

Application of Fleshing to Upflow Anaerobic Sludge Blanket Reactor for Biogas Generation

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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PDF icon application_of_fleshing_to_upflow_anaerobic_sludge_blanket_reactor_for_biogas_generation.pdf

Biomethanation of Fleshings and Sludge from Tannery Effluent Treatment Plants

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

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PDF icon biomethanation_of_fleshings_and_sludge_from_tannery_effluent_treatment_plants.pdf

Costs of Tannery Waste Treatment

Towards the end of the 20th century the tanning industry has made a considerable progress in controlling the environmental pollution caused by its activities, yet the situation varies from country to country and even from region to region within some large countries. Some tanners in industrialized countries hold the view that lax environmental regulations and poor enforcement account for lower production costs, higher competitiveness and hence further expansion of the tanning industry in developing countries.

This study compares the costs of treatment of tannery effluents, including indicative investments costs in selected industrialized and developing countries. While the figures concerning the investment and operational costs by now are quite obsolete and technologies change, the comparisons of the cost structures are still quite elightening.

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PDF icon Costs of Tannery Waste Treatment, J. Buljan

Desalting of Raw Hides/Skins and Reuse of Dusted Salt in Pickling Operation

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.

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PDF icon desalting_of_raw_hides_skins_salt_reuse.pdf
PDF icon Fact Sheet: desalting of raw hides and skins

Multiple Stage Evaporation System to Recover Salt from Tannery Effluent

UNIDO through its Regional Programme for Pollution Control in the Tanning Industry in South-East Asia has been actively looking for solutions to tackle saline tannery effluent. The following technologies have been tested at pilot scale demonstration units (PDUs):

  • Mechanical / manual removal of excess salt from wet salted hides and skins
  • Reverse osmosis (RO) of treated tannery effluent
  • Improved (accelerated) solar evaporation
  • Recycling of floats in the beamhouse
  • Use of ultrafiltration in tannery effluent.

This report provides preliminary estimates of costs of setting up a multistage evaporation system for recovery of salt from the concentrate (reject) resulting from the Reverse Osmosis (RO) of treated effluents..

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PDF icon multiple_stage_evaporation_for_salt_recovery_from_effluent_rv_2.pdf

Accelerated Evaporation of Saline Streams in Solar Pans

Total dissolved solids (TDS), specifically chlorides, in effluent are a major concern for its discharge into surface waters and its use for irrigation. Conventional treatment systems do not help reduce TDS in the industrial effluent. Taking advantage of the sunshine available for most part of the year, tanneries in Tamil Nadu, India, were required by the regulatory authority to segregate highly saline effluent (soak and pickle streams)  and evaporate it in solar pans. Due to very dissapointing results of evaporation in solar pans attempts have been made to accelerate the evaporation by simple means like combination of improved warming of the effluent and use of sprinklers. This paper reports on results of these pilot scale tests carried out under UNIDO Regional Programme in India during late 90's.

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PDF icon accelerated_evaporation_of_saline_streams_in_solar_pans.pdf

Environmental Aspects of Footwear and Leather Products Manufacture

The survey is intended to cover the environmental impacts and health issues of the footwear and leather goods industries with particular reference to solid waste, air pollution and chemicals. The review covers quantification of solid wastes, technology available for reducing environmental impact and health risks and legislation. It was presented during th 13th UNIDO Leather Panel, Bologna November 1997.

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PDF icon Environmental Aspects of Footwear and Leather Products Manufacture

Wastes Generated in the Leather Products Industry

The present report provides production ratios of solid wastes in leather, footwear and other leather products manufacture and analyse why such wastes are produced and analyses possible solutions in order to reduce the quantity of waste, or to recycle them. 

The report was prepared by C.T.C. for the 14th UNIDO Leather Panel session.

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PDF icon Wastes Generated in the Leather Products Industry

Benchmarking in the Tanning Industry

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.

 

 

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PDF icon Benchmarking in the Tanning Industry

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