Leather/Skin/Hide Processing Industry - Environmental Clearance

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Leather / Skin / Hide Processing Industry (Tannery)Tanning with organic tanning agents, using polymers or condensed plant polyphenolswith an aldehydic crosslinker, can produce mineral-free leather, matching the highhydrothermal stability of chrome leather. However, they do not have the samecharacteristics as chromium-tanned leather, because they are much more filled andhydrophilic.Metal-free leathers are being successfully used to produce high-quality, specialty leathers,for example, automotive leathers with good thermal stability.Semi-metal tanning can produce chrome-free leather, with equally high hydrothermalstability. It is a combination of a metal salt, preferably but not exclusively Aluminum (III) ,and a plant polyphenol containing pyrogallol groups, often in the form of hydrolysabletannins.A life-cycle analysis of each process needs to be taken into account.Post-tanning operationsWhen the use of chromium is required for retanning operations, the same considerationshould be given as for chrome tanning. Absence of environmentally unsound dyestuffsespecially those containing benzidine and other banned aromatic amines and ofhalogenated oils in fat liquors, form essential elements of cleaner processing. High levelof exhaustion for syntans, dyes and fat liquors are also to be considered in each case, thechemical principles and conditions for reaction with the leather must be optimized.Finishing operationsThe use of water-based finishing is fundamental for a cleaner process, but the inherentneed to use crosslinkers should be kept in mind. Chemicals used in finishing must notcontain any environmentally undesirable heavy metals or other restricted products. Waterbasedformulations (containing low quantities of solvent) are available for spray dyeing.Finishing products have to meet the current limits imposed by environmental and workershealth regulations. The equipment used is extensive. Roller coating or curtain coatingmachines are more desirable from the environmental point of view, but they cannot beused for all type of leather. For other types, spraying units with economizers and HighVolume Low Pressure (HVLP) spray guns can reduce discharges to the environment.3.4.2 Waste minimisation options3.4.2.1 RecyclingRecycling technologies have been used for long time in vegetable tanning processes,indeed the conventional counter-current method incorporates recycling as fundamentalelement of the technology.Simple recycling technologies need some control to prevent any deviation in the tanneryprocess. A laboratory with basic analytical equipment is desirable.3.4.2.2 Beam house processTo reduce the volume of saline effluents, particularly if the segregated float needs to beevaporated or specifically processed, it is possible to reuse the soaking float in a counterTGM for Tanneries August 20103-20
Leather / Skin / Hide Processing Industry (Tannery)current method, analogous to vegetable tanning. Here, the pelts progress into cleaner floatand the contaminated floats move towards the dirt soak. Only the dirt soak liquor, inwhich dirt and salt are accumulated are discharged to waste and treatment. This decreasesthe amount of water to be evaporated, when salinity is restricted, and reduces the presenceof biocides in effluent. However it does not solve the problem of what to do with the dirtsoak solution. Lagooning where feasible reduces the volume, but salt remains.The unhairing-liming float can also be reused for the next process. It must be taken intoaccount that the recovery rate of the liming float should not exceed 75 % in order to limitthe nitrogen concentration. Besides recycling materials (pumps, fine screening, storagetanks), it is sometimes necessary to warm the float before reuse and also to screen or skimit in order to eliminate undesirable floating solids and to remove hair and grease from thesurface. Without any sedimentation, an industrial recycling process can save 35 to 40 %of sodium sulphide and 40 to 45 % of the lime (with classical process quantities of 2.5%). Excessive quantities of lime should be avoided during the process. It is worth to recallin this regard that the theoretical requirement for bovine hide is about 1.2%.3.4.2.3 Tanning processa) Degreasing floatWhen sheepskins are solvent degreased, recycling of the residual solvent after distillationis currently operated. Furthermore, the extraction brine is also easy to reuse for saving ofsodium chloride.b) Pickling floatRecycling of pickling float has been proven to be highly satisfactory in terms of saltsavings and partly for acid savings. There is no great difficulty if density and acidity ofthe float can be regularly controlled.c) Tanning floatThe most common practice is to carefully collect the residual tanning float, to filter it, toadjust its acidity, and to reuse it as a new tanning float before adding fresh chromiumsalts. The recovered volume may be more than required for subsequent tanningoperations, but it is possible to reuse the liquor in post-tanning processes.Another possibility is to use the tanning float for a pre-tanning process. In this case, 60 %of the residual chromium can be recovered.When pickling and tanning are carried out in the same float, it is also possible to collectthe residual tanning float, to filter and acidify it and reuse it as a pickling float.3.4.2.4 Post-tanning processIt is much less feasible to recycle post-tanning floats since the chemical conditionrequired for the steps may be different and steps tend to be conducted sequentially in thesame float. Therefore, the problem of contamination is compounded, especially sincethese steps vary greatly, even in a single tannery. Thus recycling technology cannot berecommended.TGM for Tanneries August 20103-21
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FORPrepared forGovernment of India
Page 4 and 5: Table of Contents3.5.2 Tannery effl
Page 6 and 7: Table of ContentsLIST OF FIGURESFig
Page 9: AcronymsIUEkglLDARLCALTLm 2mg/m³mg
Page 12 and 13: protocol/ related regulations/ and
Page 14 and 15: IntroductionOperational issues1.1 P
Page 16 and 17: Introductionfor 27 industrial and r
Page 18 and 19: Conceptual Facets of EIA2.2 Polluti
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Operational Aspects of EIAIf the Au
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5.STAKEHOLDERS’ ROLES ANDRESPONSI
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Stakeholders’ Roles and Responsib
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ANNEXURE IGeneral Standards for Dis
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18. Hexavalent chromium (as Cr+6) m
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2. The user should make efforts to
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ANNEXURE IIForm 1 (Application for
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1.6 Demolition works?1.7 Temporary
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3. Use, storage, transport, handlin
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5.6 Emissions from incineration of
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9. Factors which should be consider
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ANNEXURE IIICritically Polluted Ind
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8 Vellore (North Arcot) (TamilNadu)
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31 Pali (Rajasthan)CEPI-73.73 (As_W
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TYPES OF MONITORING AND NETWORK DES
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knowledge of the sources of the pro
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GUIDANCE FOR ASSESSMENT OF BASELINE
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AttributesSamplingMeasurement Metho
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AttributesSamplingMeasurement Metho
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ANNEXURE VISources of Secondary Dat
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Information8. Nature of Terrain, to
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Annexure IVB: Summary of Available
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13. Department of Ocean Development
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19. Indian Meteorology Department S
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32. National Botanical Research Ins
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ANNEXURE VIIForm through which the
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ANNEXURE VIIIComposition of EAC/SEA
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I)Primary treatment is the first st
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compounds degraded in step 1) and t
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New Machineries:These are a few pho
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REFERENCESMinistry of Environment a
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IL&FS Ecosmart LimitedFlat # 408, S
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