Technology in Leather Industry by vuh88690


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   Low Waste Technologies and Treatment Waste
    in the Leather Industryin Developing Countries

                  Prepared by: Jakov Buljan
            Senior Industrial Development Officer
United Nations Industrial Development Organization (UNIDO)
                                                                              TABLE OF CONTENTS

               '    .'::?"'.              .   I       THE POLLUTION LOAD QUANTIFIED                           1
           -:               .             .

                                                      RELOCATION OF POLLUTION                                 2

                                                      NORMATIVE ASPECTS OF THE ENVIRONMENTAL         3
                                                      PROTECTION IN THE LEATHER SECTOR IN DEVELOPING

                .           ,        ;.I".
                                      . ,             THE POTENTIAL FOR INTRODUCING CLEANER                   3
      .' ;'i+&.,        . ;:,,,,:
                                ,                      TECHNOLOGY
. , .,         ,I   G,           +,p:.                'METHODS
      .        '                :.;I,'                     Preservation                                       3
                 , .' .
                                                           Beamhouse                                          4
                    j       $&.     )'i           i        Tan-yard                                           4
      ,:                I   , f2.V:
               .. .
      .,   ., .i.:..
                                   c 5,.                   Wet anddry finishing                               4
           ',.. ,q:$
           . I

              . .; ~.,.
                                                           Conversion of solid waste saleable   by-products   4
       , , . ..
           '            ',, '
                                                      BARRIERS TO INTRODUCING CLEANER TECHNOLOGIES
                                                      AND UTILISATION OF BY-PRODUCTS                          5
                                                          Technical considerations                            5
                                              . .         Economic considerations                             5
                                                          Social considerations                               6
  .    . ., .           .                     .
       '                    '                         PRACTICAL EXPERIENCE GAINED - KEY ISSUES                    6
                                                          Legislation, monitoring, enforcement                    6
                                                          Human resources                                         7
                                                          Common effluent treatment plants (CETPs)                7
                                                          The cost of treatment                                   8
                                          .*.             Solid waste and sludge disposal,landfills               8
                                                          Funding of ETPs and CETPs                               8
                                                          Typical constraints in collecting and
                                                          determining basic plant                                 9
                            ..                %, .           and
                                                          data plant      design

Is the environmental pollution emanating from the tanning industry

In order to assess this the magnitude   of world production must be
quantified.Thegloballycomparablefigurespublished          by F A 0 in
their 1989 statistical compendium are used for this purpose1 and are
as follows.

                                                   1985187 average

World. hide production input                       4,926,600 t w/s
World sheepskin production input                     934,000 t w/s
World goatskin production input                      355,000 t w/s
World pigskin production input                       600,000 t w / s

On the basis of a yearly input ("soak") of about 6.8 million tomes of
wet salted hides and skins world-wide, it can be estimated that about
3,427,000t of various           are annually leather
                       chemicals used          for
processing. A significant part of this amount is not actually absorbed
in the process and is discharged into the environment.

With an average yield of 45-50 m3 of waste water per tonne of raw
hide, the total amount of liquid effluent from light leather processing
only (almost 90 per cent of overall production) is over 300 million m3
a year containing about


COD                                                1,470,000
BODS                                                 610,000
Suspended solids                                     920,000
Chromium                                              30,000
Sulphide                                              60,000
Solids in sludge                                     730,000


Raw trimmings                                        730,000
Fleshing                                             730,000
Waste blue split                                     700,000
Trimmings and shavings                               610,000
Buffing dust                                          10,000
Finishedtrimmings                                    190,000
. .


           Althoughthemainattention,especially          in developing countries, is
           focused problems              with use
                              associated the                     of sulphides  and
           chromium,other,possiblymoreimportantpollutantsderived                from
           most leather processing are electrolytes (mainly NaC1, sulphate and
           other salts) and organics (synthetic and natural).

           Electrolytes are the biggest component of most tannery effluent, they
           are the most difficult to remove, yet too often their insidious effects
           are ignored. Most leatherprocessingrequireselectrolyte           tocontrol
           swelling, it is also brought into the waste streams as a component of
           preparations. In total it accounts for 70 per cent of the total solids load
           in a tannery processing salted hides.

           Treatment               on other in
                     technologies, the hand,effect      reduce
           solid forms. Therefore, the pollution threat is being transferred from
           receiving waters to receiving land because sludge can adversely affect
           the quality of soil and groundwater.

           In light of above figures and given the deeply rooted perception of the
           tanningindustryasveryoffensive         to humansensesandresulting
           pressures from the environmental authorities and general public, it is
           notsurprising that nowadaysecological'considerationsdominate
           much of the leather industry's thinking and research work.


           About one-half of the pollution load calculated earlier is produced in
           developing          The
                     countries. substantialrelocation                  of leather
           production from industrialised theto developing countries,
           which occurred between the 1960s and the 1980s ("The Big Shift") in
           effect moved the most highly polluting part of the process away from
           the OECD countries under pressure of increasing cost of labour and
           cost of effluenttreatmentinstallationsandoperations.Thisprocess
           was accelerated by a combination of export restrictions for raw hides
           and     and
              skins various            for
                              incentives higher processinglevels
           provided in developing countries.

           The prospect of the global production of about 2,400 million rn2 of
           leather by theyear 2000 presents a considerablechallenge tothe
           industryconsideringtheharmfulnature           of some of thechemicals
           applied in leather processing and the inevitable emission    of effluent
            the     solid volatile
           in liquid and               with,
                                 forms sometimes,      almost
           irreversible damage to the environment.
. .
  .'.   .



                 In manycountriesenvironmentallawshavebeenpassedrapidly.
                 Unfortunately, however, their implementation has not always been
                 possibleeither        the have too
                               because laws been ambitious                             or
                 unrealistic, or because they have lacked effective instrumentation and
                 institutionalsupport.Moreover, some               laws
                                                    environmental have
                 failed because they d o not match the economic reality of the country
                 or region, or because they do not take the institutional capabilities of
                 the society that has to implement them into consideration.

                 Ingeneral,environmentallegislation      in developingcountrieshas
                 Existence of national,regionaland local environmentalauthorities
                 withingovernment  structures the
                                             with             legal power to enforce
                 environmentallawsandmakedecisions         at differentlevels;reliable
                 field                     and       and presence
                                assessment research the                                of
                 individuals       of
                            capabledesigning  environmentalpoliciesand
                 regulations and of technical experts who can mitigate environmental;
                 problems and monitor environmental performance, is essential.


                 Owing to the    nature    of leather production,      in most
                                                                   even the
                 sophisticatedtannery,technologyremains          - to a certainextent - a
                 mixture of craft and science and strictly speaking there      is no basic
                 tannery process. As a corollary, it is not possible to simply replace the
                 traditional technology with an entirely new "clean" process.

                 The two main sources      of pollution in a tannery are unhairing and
                 tanning,Theseshouldbethe           first places to considerintroducing
                 cleaner leather processing technologies.

                 under conditions prevailing in developing countries are:

                 4.1    Preservation
                       -      processing of driedhidesandskins
                       -      use of greenhidesfromabattoirswithout  the necessity of
                              temporary preservation
                        -     useofsafe biocides in curinghidesandskinsandwet
                              blue leathers
           -     partialsalteliminationbyusing    a drum type shaker
           -       fleshing
           -     hair-saving,                especially
                             unhairing-liming,       enzymatic
                 unhairing of skins
           -     ex-limeinstead of ex-wet bluesplitting
           -     ammonium-free, C02, delimingforlightpeltscombined
                 with the use of ammonium free bates.

                                                     inste ad of organic
                 solvents; reuse of solvents
           -     limiteddirectrecycling of chrome floats
           -     chrome         with
                        recyling precipitation
           -     use of high  chrome exhaustion      primarily
                                               systems       for
                 lime splitted hides

     4.4   Wet and dry finishing
           -     avoidance of heavy        and
                                      metals benmzidine   containing      -
           -     avoidance of halogenated fatliquors    ~

           -     high level of exhaustion of syntans,dyesandfatliquors
           -     use of water based finishes; at leastbase and middle-coats
                 should be made of aqueous polymeric dispersions and
                 contain safe crosslinking agents
           -                 coating tec-hnique
                 use of roller

     4.5   Conversion of solid waste into saleable by-products

           Tanneries can maximise their returns on residues from sludge
           andsolidwastes by: investigatingthe feasibility of extracting
           methane, saving hair for conversion into felt or use as a slow
           trimmingsintogelatine,proteinpowdersandcollagen                for
           sausage       and        and
                  casings medical surgical    films;turning
           tannedwasteintoleatherboard,       filter media, non-wovens and
           otherend uses. By commercialisingsolidwastes,the           cost of
r.         effluent treatment can, to some extent, be covered.

5.1   Technical considerations

      The adoption of low-waste technology often requires a
      alteration of most tannery processes while, at the same time,
      ensuring the
               that ultimate
                           productretains marketable
                                        its                                             I
      properties.Therefore,    if atanner is producing     consistent
                                                           a                            I

      quality of leatherwhichsatisfieshiscustomersusing          a process          I
      whichmaywastewater,energyandchemicalutilisation,he                            i
      may altering
         resist     his
                     operations                       to comply  with

      Generally speaking,low-wastetechnologies require
                                                     better                     I
      skilled personnel and closertechnicalcontrolthanconvention               1

      processing. Thus, the lack of properly trained staff at different
      levels remains one of the crucial constraints.                -....---I

      Virtuallyeverywherethere       is aproblem of remoteness of
      government-backed R&D facilities the     fromeveryday
      practicalities of leather-making and in transferring technology
      from laboratory and pilot plant of an R&D to the industry.

      For the practicing tanner there is a world of difference between
      results claimed by an R&D centre or a chemical supplier and
      whathappens inreality.Notonlymight             thetechnology be
      suspect, but differences in the costs of chemicals and/or energy
      can have a significant impact on process economies in different
      (at the industrial scale) clean technologies with quantification of
      reductionsinpollutionachievableandanindication              of a n y
      disadvantages and data on investment and operation cost.

5.2   Economic Considerations

      The cost of introducing a cleaner processing method may be
      prohibitiveandbeyond thereach of a small-scaletanner.The
      price of thespecialdrumforhair-saveunhairingwiththe
      necessary auxiliary equipmentmaybetwice          as muchasthe
      convention      Enzyme
                  drum.        unhairing     very
                                        needs precise
      controlandconsistency       of all parameters(pH,temperature,
      float which           is only       to
                                   possibleachieve           in rather
      sophisticated tanneries and is associated with higher production
      costs (partly off-set by lower waste water treatment expenses).
      High chrome  exhaustion tanning        very
                                     requires expensive,
      specialchemicals (normally proprietaryproducts),             well
      equipped drums and strict process control.

             Realistic,                   objectives     shouldbeinstituted
             rather than unattainable standards resulting from political      or
             evenemotional         Good
                          motives. cooperation    betweenthe
             industryandgovernmentauthoritiesconcerned              is therefore

             enforcementofthestandards        is notputintoeffect,    i t is
             understandable that the required environmental standards may
             not be met.

      -6.2   Human resources

             Mostdevelopingcountriesarefacinganacuteshortage                  of
             maintaining effluent treatment plants for tannery waste.     Even
             in the industrialised countries, design     of tannery ETPs is not
             quite a perfected skill: most plants (especially CETPs)have been
             deficiencies original        or
                                    design,improve the
             purification level to meet increasingly stringent standards, or

             Appropriate training and education pkogrammes are needed to
             cater to theneedsoftechnicalpersonnelatvariouslevels
             (operating,supervisory,managerialanddesign).There             is an
             urgent need to precisely identify a training curriculum, type of
             faculty and infrastructural facilities required for this purpose.
             The       expertise facilities
                existing         and      available some
             developing countries could be taken into consideration to cater
             to regional needs.
      6.3    Commoneffluenttreatmentplants        (CETPs)

             Jointeffluenttreatmentplants,possiblycombinedwith               a
             central chrome recovery unit, are very often the best solution
             for tannery clusters, as a rule consisting of small and medium-
             scale units. Combined with domestic waste, they offer technical
                         with economy
             advantages an                      of scale.However design,
             installation and operation of CETPs, including distribution of
             operation costs, is much more complex than that of individual,
             possibly very large units.
6.4   Solidwasteandsludgedisposal,landfills

      Very often the problems of transport and safe disposal of solids
      and, more recently, of huge amounts of sludge generated by
      ETPs and CEPTs isunderestimatedz.Ontheotherhand,
      standards, disregarding the fact that local authorities concerned
      have not provided suitable sites/landfills.

6.5   The cost of treatment

      Effluent treatment costs depend on specific site conditions, and
      vary within a very wide range. In Europe they are estimated to
      be of the order of US$5 to 15 per cubic meter of effluent or 4 to15
      per cubic meter of effluent or 4 to 6 per cent of the finished
      leather production cos$. Initial treatment costs may not result
      at this level of on-cost in developing countries, but as standards
      instringency        in
                   and/or enforcement           they
                                        advance, will
      inevitably increase.

      Removing oxygen demand is normally the largest component
      of effluenttreatmentcosts:currentlyinthe         UK, thecost is
      US$1-2 per m3 of effluent treated a t 3,000 m g / l COD and 500
      m g / l SS, whether on-site or in a mixed treatment system.

      The individual tannery's share in the CETP's operation cost is
      in industrialisedcountriesalmostalwaysdeterminedonthe
      basis of actual effluent volume and pollution load using rather
      complex formulae.

6.6   Funding of ETPs and CETPs

      Despite strong demands, especially from small-scale tanners, as
      a rule there is no government support in the form of financing
      or         soft-term       for
                          funding introducingcleaner
      technology and/or setting up ETPs. A possible exception is the
      IndianGovernmentwhichprovides            25 percent,individual
      states provide an additional 25 per cent and tanners are expected
      to pay 15 to 20 per cent of the cost of establishing common
      treatment facilities.The remainder is made up of loans from
      financial            Once are
               institutions.                    the of
                                they operating, cost
      maintaining  effluent
                  the    treatment       the
      responsibility of the tanners.

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