of 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 -: . . I . RELOCATION OF POLLUTION 2 NORMATIVE ASPECTS OF THE ENVIRONMENTAL 3 PROTECTION IN THE LEATHER SECTOR IN DEVELOPING COUNTRIES . , ;.I". ; . . , THE POTENTIAL FOR INTRODUCING CLEANER 3 .' ;'i+&., . ;:,,,,: " , TECHNOLOGY . , ., ,I G, +,p:. 'METHODS ,;.'*.&# . ' :.;I,' Preservation 3 .. , .' . t' Beamhouse 4 j $&. )'i i Tan-yard 4 ,: I , f2.V: .. . ., ., .i.:.. ,'";:t, .e c 5,. Wet anddry finishing 4 ',.. ,q:$ . I . .; ~.,. ' into 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 THE POLLUTION LOAD QUANTIFIED Is the environmental pollution emanating from the tanning industry relevant? 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 Tonnes COD 1,470,000 BODS 610,000 Suspended solids 920,000 Chromium 30,000 Sulphide 60,000 Solids in sludge 730,000 plus Raw trimmings 730,000 Fleshing 730,000 Waste blue split 700,000 Trimmings and shavings 610,000 Buffing dust 10,000 Finishedtrimmings 190,000 . . -2- Althoughthemainattention,especially in developing countries, is on 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 chemicals,e.g.chrometanningslats,syntans,dyestuffsandbating 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 pollutantsintheliquidformandconvertthemintosemi-solidor 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. 2. RELOCATION OF POLLUTION About one-half of the pollution load calculated earlier is produced in developing The countries. substantialrelocation of leather the 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. . . .'. . -3- 3. NORMATIVE ASPECTS OF THE ENVIRONMENTAL PROTECTION I N THE LEATHER SECTOR I N DEVELOPING COUNTRIES 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 advancedfasterthanactivitiesonmanagementandenforcement. Existence of national,regionaland local environmentalauthorities withingovernment structures the with legal power to enforce environmentallawsandmakedecisions at differentlevels;reliable laboratories,equipment,infrastructureandeconomicresourcesfor monitoring, 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. THE POTENTIAL FOR INTRODUCING CLEANER TECHNOLOGY METHODS 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. Amongthelowwastetechnologies,possiblythemostpromising 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 green - 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 ,ants 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 - dyes - 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 releasenitrogenfertiliser,turningwastesplitanduntanned trimmingsintogelatine,proteinpowdersandcollagen for sausage and and casings medical surgical films;turning fleshingsintoglue,animalfeedproteinandfertilizers,and tannedwasteintoleatherboard, filter media, non-wovens and otherend uses. By commercialisingsolidwastes,the cost of ,' r. effluent treatment can, to some extent, be covered. -5- BARRIERS TO INTRODUCING CLEANER TECHNOLOGIES AND UTILISATION OF BY-PRODUCTS 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 environmentaldemands. Generally speaking,low-wastetechnologies require better I I skilled personnel and closertechnicalcontrolthanconvention 1 processing. Thus, the lack of properly trained staff at different I 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 countries.Thisrequiresinformationonreliable,well-proven (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, etc) 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. -7- scientifically-based Realistic, objectives shouldbeinstituted rather than unattainable standards resulting from political or evenemotional Good motives. cooperation betweenthe industryandgovernmentauthoritiesconcerned is therefore essential. Themeansforproperenforcementareimportantiflegal enforcementofthestandards is notputintoeffect, i t is understandable that the required environmental standards may not be met. -6.2 Human resources Mostdevelopingcountriesarefacinganacuteshortage of technicallyqualifiedpersonnelforoperating,monitoringand 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 modifiedseveraltimesafterinstallationeithertoeliminate in the deficiencies original or to design,improve the purification level to meet increasingly stringent standards, or both. 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 in developing countries could be taken into consideration to cater to regional needs. .,p 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. -8- 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, environmentalagenciesinsistoncompliancewithdischarge 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 extending 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 is facilities responsibility of the tanners.
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