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Journal of Cleaner Production 19 (2011) 221e228

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Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Ecological utilization of leather tannery waste with circular economy model

Jing Hu a, Zuobing Xiao a,*, Rujun Zhou a, Weijun Deng b, Mingxi Wang a, Shuangshuang Ma a

a School of Perfume and Aroma Technology, Shanghai Institute of Technology, Shanghai 200235, PR ChinabBASF Leather Technical Service Center, Shanghai 200137, PR China

a r t i c l e i n f o

Article history:Received 30 November 2009Received in revised form13 September 2010Accepted 28 September 2010Available online 8 October 2010

Keywords:Circular economyLeather tanneryWasteEcological utilization

* Corresponding author. School of Perfume and AInstitute of Technology, Shanghai 200235, PR China.þ86 21 54487207.

E-mail address: xzb@sit.edu.cn (Z. Xiao).

0959-6526/$ e see front matter � 2010 Elsevier Ltd.doi:10.1016/j.jclepro.2010.09.018

a b s t r a c t

Circular economy (CE) focuses on resource-productivity and eco-efficiency improvement in a compre-hensive way, especially on the industrial structure optimization of new technology development andapplication, equipment renewal and management renovation. The leather industry on the one sideboosts the local economic development, on the other side however leads to the tremendous environ-ment pollution and biological chains destruction. The CE model has been implemented as a new way ofraw materials, water and energy consumption reduction in the leather industry. Reduce, Reuse, Recycleand Recover of the tannery effluents have been discussed in detail according to the different operationprocesses. The successful treatment approaches with analysis in the aspects such as wastewater, solidwaste, sulfide, Chemical Oxygen Demand (COD), ammonium salt, chloride and chrome of the leathertannery with CE model provide guidance for the sustainable development of leather industry in thefuture.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

Industrial ecology (IE) (Frosch and Gallopoulos, 1989; Korhonen,2004a,b) is an environmental management concept to call atten-tion to a biological analogy: the fact that an ecosystem recyclesmost essential nutrients, using only energy from the sun to drivethe system (Korhonen, 2000). In ecosystems materials are recycledbiologically, in the sense that each species’ waste products are the“food” of another species (Ayres and Ayres, 1996). The conceptoffers an invitingly concrete way to integrate environmentalmanagement and meet environmental, economic, and communitydevelopment goal (Chertow, 2000). So IE focuses on material andenergy input-output flows of industries, companies, products orregions aiming to make use of the wastes.

Porter (1996), Porter and Van der Linde (1996) reported that theindustrial district of Kalundborg in Denmark has reached aneconomic environment winewin situation utilizing each other’swastes. Korhonen and Karvonen (1999) analyzed the imple-mentation of IE in the paper industry. Reijnders (2007) reportedthat the cement industry used a variety of secondary materials andfuels, thus fulfilling the role of scavenger in IE. Reduced levels ofhazardous elements in secondary materials and fuels used in

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cement production contributed to the reduced environmentalreleases of such elements during cement-derived product lifecycles. IE not only explains how industrial systems operate but alsosuggests how the industrial system should operate to evolvetowards a sustainable configuration (Boons and Roome, 2008).

With the promise of the IE understood, and with a significantarray of conceptual and theoretical guidance already available, theconcept of CE first proposed to Chinese Central Government byscholars in China in 1998 has been formally accepted in 2002 by theChinese Central Government as a new development strategy aimedat environment protection, pollution prevention and sustainabledevelopment (Bilitewski, 2005). China has almost a decade ofexperience in developing and implementing a CE. The NationalDevelopment and Reform Commission (NDRC) was appointed bythe State Council to take over the duty of promoting CE in 2004. Bydoing so, CE has been elevated to play a more important role inChina’s economic development (Yuan et al., 2006).

Then, the traditional industrialization produces negativeindustrial byproducts such as pollution and environmental degra-dation, which should be meliorated via applying the CE. Thetraditional leather industry characterized with high input andconsumption increases the prominent economic efficiency, but italso leads to the tremendous environment pollution, biologicalchains destruction and the huge waste of resource. Statistically thecapacity of world leather is about 1.5 � 1010 kg hides and skins peryear. The average wastewater discharge is more than 1.5 � 1010 kgper day. Solid waste generation from tannery process is estimatedas 6 � 109 kg per year (Rajamani et al., 2009).

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228222

With the quick development of economy, the social awarenessincreases more to the health care and the ecology. The new legis-lations regarding leather manufacture drive the leather productionmore ecological as well. At present, almost all the countriesincluding the developing countries have introduced the pollutioncontrol standards similar to the standards adopted in United States,United Kingdom, European Union and other developed countries.In view of the seriousness of environmental issues, cleanerproduction and implementation of Common Effluent TreatmentPlants (CETPS) in tannery clusters, relocation of tanneries fromurban towns to designated industrial areas with major investmenton environmental protection had been done in countries such asSpain, Turkey, India and China et al. Currently environment is themajor area of research carried out by the leather research institutesand universities. The leather dealt with cleaner production andwaste management is a major issue for the sustainable develop-ment of the leather industry (Rajamani et al., 2009).

Hence, CE consciousnessmust be raised on the leather processes,the ecological chemical product choice and the tannery wastetreatment. In this paper, the content of the CE model is provided onthe basis of the theories of CE at first. Then, the ecological imple-mentation of the wastewater, solid waste, sulfide, Chemical OxygenDemand (COD), ammonium salt, chloride and chrome from theleather tannerywastewith theCEmodelhas beenanalyzed indetail.A successful case of CEmodel in the leather tannery companywill beintroduced. The paper concludes that the ecological utilization of CEmodel in leather tannery waste will have great potential for thedevelopment of leather industry in the future.

2. CE model

CE is an economic growth and development system to integratethe economy resource and the environment factors based on thematerial metabolism mode, which has the mechanism of efficientuse and waste stream feedback (Zhou and Liu, 2005). Kenneth(1965) suggested for the first time in 1965 in his Spaceship Earththat the earth is single like spaceship in which a cyclical ecologicalsystem is capable of continuous reproduction. CE later was used asa term by Pearce and Turner (1990) to describe the sustainableenvironment-economic development and basic principle rulers. In1980s CE was brought up to the legislative levels by the developedcountries. A typical example is that Germany issued “recycleeconomy and wastes handling law” in 1996. Due to the increasednature resource consumption and pollution resulting from highspeed of industrialization and urbanization, CE has been developedand promoted in China as new development strategy, neweconomic development pattern in an in-depth way. At present,a great number of economic and informational instruments havebeen used to perform the CE. These include pollution levies, envi-ronment taxes and eco-labeling; environmental management toolssuch as cleaner production, energy and water cascading; life cycleassessments and the “3R’s” of waste reduction (Geng et al., 2009).The tools have been carried out in China through favorable policiesdeveloped by organizational structures, such as powerful stake-holder networks using system-wide integrated resource manage-ment systems (Mao and Kang, 2005). Qu (2002) described that allCE activities should be inspired by ecological principles to maxi-mize the resource efficiency and to minimize the waste dischargeand that CE is essentially one kind of ecological economy in China.Ma (2005) pointed out that CE is characterized with low resourceconsumption, low waste discharge and high efficiency, and thebasic principles are Reduce, Reuse and Recycle. Admittedly, CE hadbeen paid more and more attention after the full development ofindustrialization with its first aim to resolve the likely shortage ofsources. It is a revolution on linear economy and viewed as a new

interdisciplinary (Xiao andWang, 2007). This concept has the sameessence as industrial ecology, implying a closed-loop of materials,energy and waste flows (Geng and Doberstein, 2008).

It has been widely recognized that CE could help improveresource productivity and eco-efficiency, reform the managementof the environment, and achieve sustainable development (Genget al., 2009; Liu et al., 2009). At a theoretical level, the CE modelfits closely with ecological modernization theory, which is “cen-trally concerned with the relationship between industrial devel-opment and the environment” (Murphy and Gouldson, 2000).These aspects are all important factors in the triple bottom lineachievement that is essential in the delivery of high environmentalstandards and quality of life.

It can be summarized that CE theory in China is promoted tochange thematerial and energy input/output flow for facilitating thedevelopment of economic system towards the principles of systemdevelopment of ecosystems. CE advocates that economy systemshould be constructed on base of material and energy flow andchanges linear throughput flow to roundput flow of matter andenergy. Imitating nature recycle, industrial recycle is to get moreefficiency on reducing the consumption of virgin resources and thepollution generation by changing the methods, material flows, newtechnologies and relevant management. The basic philosophy in theCE approach is to enhance the emergence of an industrial andeconomic systemthat relies on cooperationamongactors andmatterandenergyflowmanagement, in that theycanuseeachother’swastematerial and energy as resources and in this way minimize thesystem virgin material and energy input. CE provides innovativeroutes tochangepresentunsustainable systemto sustainable system.In industrial recycle, there are 3R’s (Circular economy law of thePeople’s Republic of China, 2008) generally standing on CE proper-ties: Reduce (Reduce the consumption of resource and the produc-tion of wastes in the processes of production, circulation, andconsumption), Reuse (use the wastes as products directly, usingwastes after repair, renewal, or reproduction or use part or all wasteas components of other products), Recycle(use wastes as raw mate-rial directly or after regeneration). As 3R originate from wastehierarchy (http://www.epa.gov/wastes/homeland/hierarchy.htm;http://www.dacorum.gov.uk/default.aspx?page¼4130), 3R’s aboveare overlapping and clearly CE in China is not rubbish economyanymore (Rather, it is a new sustainable economic pattern.), there isneed to modify the definition of these principles. To the author’sunderstanding, 4R, four-level interrelated and interdependent prin-ciples of CE can be described as: Level 1, Reduce (Reduce theconsumption of resource and the production of wastes in theprocesses of production, circulation, and consumption); Level 2,Reuse (use the wastes as products, either in the same function or inanother); Level 3, Recycle (use the wastes as raw materials aftersimple treatment such as collection, separation and suitable modi-fication, during which core physical and chemical properties shouldremain); Level 4, Recover (use the wastes as products, or raw mate-rials after technical treatment during which the core physical orchemical properties change in relation to the feeding condition).

While Reduce is viewed as the beginning control of theproduction and consumption process, the rest can be regarded asend-of-pipe controls with gradually increased complexity ofre-treatments. From this point, Reuse, Recycle and Recover mayhave intersections in the practical activities. With the considerationof more processes or whole system, Recycle and Recover are aimedto Reuse and further to Reduce. Therefore, there is no need todiscriminate them strictly and exactly, for all reduce the drainagesto ecosystem (Wu, 2006).

The CE model is demonstrated in Fig. 1, where process refers toall activities of resource/energy productions and consumptions.The span between process A and process B is determined by the

Fig. 1. Recycling economy model.

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228 223

scope of CE. For example, process B can follow process A or ante-cede process A. The arrangement of both processes is flexible basedon the output, their intrinsic properties and the following recyclingnetwork systems. Normally, process B differs from process A. In thecase that process B is the same as process A, this model can betransferred to Fig. 2. Similarly to IE, it is necessary to analyze thesystem at smaller scales to understand the underlying mechanism,and at large scales to grasp the context for a holistic approach.

The economic activity can be analyzed with CE model in threesteps including reduce analysis, process analysis and reuse analysis.First of all, the influence of Reduce on the input should beconfirmed. Reduce can be carried out with priority when it does notgive any disadvantages or these disadvantages can be neglected.However, when the effect of Reduce on the input cannot be ignored,the other conditions should be changed to make the output of theprocess similar with that of the traditional process, which meansthat the process should be analyzed. This is the second step wewant to emphasize. The last step is reuse analysis including Reuse,Recycle and Recovery. All of them supply a process with comple-ment of materials or energy. The three step analysis is corre-sponding to the basic elements for Zero Emission strategies(improvement of total productivity, separation of output productsand waste, creation of network systems to coordinate input andoutput) (Pauli, 1998; Baumgarter, 2007). The reuse analysisincludes separation of output products and wastes, creation ofnetwork systems to coordinate input and output where the formeris precondition for the later and individual reuse may determinethe technology of separation and its cost.

During the implementation of this model, the following issuesshould be taken into special account: (a) 4R principles should not bethought of as being in competition with EPA’s (EnvironmentalProtectionAgency) reduce/reuse/recycle hierarchy (http://www.epa.gov/wastes/homeland/hierarchy.htm; http://www.dacorum.gov.uk/default.aspx?page¼4130), but instead as providing an analyticalframework to better implement CE strategy. (b) networks integrationof the application of 4R, i.e. inwhich process the recycledmaterial orenergy can bemore efficiently used; (c) the difficulty and complexityof 4R. Preference givenaccording to the establishedhierarchy (http://www.epa.gov/wastes/homeland/hierarchy.htm; http://www.dacorum.gov.uk/default.aspx?page¼4130) generally offersoptimumcost-efficiencyoptions. Consider thegradual increasedcostof retreatment from Reuse, to Recycle and Recover. However it is notalways the case. For example, Reduce in the use of certain materialsmay be impossible for some specific application and under suchcircumstances, Recycle or Recover might be the optimum option tobe focused on.

Fig. 2. Special circular economy model.

This system is close when the recycled materials and energy canbe reused completely, that is, there is “zero” discharge and nopollution to the environment since all the industrial outputs havebeen reused in this process or other processes and will not bedischarged directly into the natural environment. In most cases, theperfect close-loop systems do not happen, however, it seems to beclear that the direction we should flow when striving towardssustainable development of economic system. On the other side,the above circle is open when the recycled materials and energy orpart of them cannot be reused. If the drainage from the open circleis discharged to the environment directly, part is tolerated in naturemetabolism, whereas other part is regarded as pollution when thenature balance is changed.

3. Overview of leather tannery waste

Abundant water and chemicals should be used in the leathermanufacture. Normally when 1 � 103 kg raw hides are transferredinto approximate 250 kg leather, 1.5 � 104e5 � 104 kg wastewaterand 450e730 kg solid wastewill be generated. Generally, 1�103 kgraw hides consume 1.5 � 104e1.2 � 105 kg water. At present, thebasic water still maintains 1.5 � 104e5 � 104 kg even with theupdated cleaner technology. Statistically 1 � 1011 kg wastewatercan be generated during the leather manufacture in China, whichobviously leads to the heavy water pollution. This waste liquid from1 � 103 kg raw hides will be transferred to 500 kg sludge (solidcontent: 40%) through the water treatment plant. Simultaneously,the wastewater produced from 1 � 103 kg raw hides to leatherincludes about 240 kg COD, 100 kg Biological Oxygen Demand(BOD), 150 kg suspended solids, 170 kg common salt, 80 kg sulfate,5 kg chromate and 10 kg sulfide (Duan, 2000).

The mainwastes focused in tannery process are shown in Fig. 3.First, the typical pollution is sodium chloride from the preservationof raw hides. Generally 1�103 kg fresh hides need 300e400 kg saltfor their preservation. So 70% salt pollutions in the tannery comefrom the raw hides. The second wastes are certain amount ofsulfide and lime not absorbed by the pelts in the liming process.Thirdly, the broken hair and epidermis in the liming and nonstructural protein in soaking and liming increase the COD and BODcontent in the water, which leads to water pollution and propa-gates microorganism for supernutrition. Besides, Nitrogen-amineproduced from liming, deliming, bating and retanning may lead tothe development of a toxic anaerobic system that kills the bacteriaof the wastewater plant. In addition, the most toxic chemical ischromium (VI) oxidized from chromium (III) in tanning. Chromium(VI) has been investigated intensively as a recognized problem andit has been shown to be carcinogenic, mutagenic and allergenic.The current legislation regarding leather imposes a maximumlimit of 3 mg kg�1 based on the leather weight. Alkyl phenolethoxylates (APEs) are nonionic surfactants used as the emulsi-fiers, the dispersing agents and the fatliquoring agents for leather.European Union has limited the application of APEs because oftheir alleged toxicity, poor biodegradability, and the liability tobioaccumulation. At last, many solid wastes are from fleshing,shaving, trimming and buffing in mechanical operation, such as,1 � 103 kg raw hides generate 70e350 kg fleshings, 225 kg shav-ings, 150 kg trimmings and 2 kg buffing dust.

4. Approach in CE utilization of leather tannery waste

4.1. Reduction of wastewater

The reduction of wastewater in tannery process can be realizedaccording to the following steps. First, the technology with lesswater is recommended to maximize the water efficiency with the

Fig. 3. The material flow chart during leather tannery.

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228224

guidance of Reduce. Specially, the washing effect is achieved withless water by proper mechanical action which relates to the load,the drum speed and float ratio instead of more fresh water andwashing time. What far more important is that 1 � 103 kg freshwater saved not only means less water cost, but less money spenton the waste effluent treatment.

The second is the control of technological conditions. With lesswater, better removal of non structural protein, dirty stuff and saltis possible with cleaner pelts in the processes before pickling andbetter exhaustion rate can be achieved with tighter and fullerleather in chrome tanning. Few chemicals in thewastewater reducethe difficulty of wastewater treatment and recycling utilizations.

Finally, Recycle is considered. Fig. 3 indicates that differentprocesses generate the various waste effluents. The main principleof Recycle is the separate collection and treatment of wastewater.Wastewater gathering system fixed on the paddle or drum andadjusting pool is necessary for the management and treatment ofthe wastes.

Further, the leather manufacture processes are investigated withCEmodel to demonstrate how to reduce the discharge of wastewateras shown in Fig. 4. Liming can be arranged after soaking directlywithout changing the float, especially to well preserved hides withless grease and salt. In the conventional process of soaking salt-preserved hides, the amount of soaking effluent discharged is 7 m3

(based on 1 � 103 kg raw hides) (Ludvik, 2000). Table 1 shows thetypical pollution components of soaking effluents. The washing floatof liming and reliming can be recycled for liming or reliming.Besides, the liming float can be reused for liming (Zhang and Lin,

2001; Qu, 1994). The amount of effluent in the typical liming andthe corresponding washing is 5e7 m3 (based on 1 � 103 kg rawhides). Table 1 shows the pollution load of liming: high COD due tothe broken non structural protein, hair and epidermis, and high lime.This float can be reused directly for liming after the simple filtrationof the solids and deposition of lime.

In recycling spent float, the additional chemicals dosage isstrictly controlled by the measurement of reused float before theprocessing, because this system in practice is not completely closedue to the evaporation of hydrogen sulfide and deposition of lime.To get better effect such as the cleanness and swelling, the processcan be adjusted slightly, for example, after several times recycling,the spent float has masking effect to alkaline, therefore, it isnecessary to reduce the dosage of liming auxiliary and add soda orcaustic soda to balance the swelling. After 10 or 20 liming floatcycles, the masking effect is too strong to continue, a new recyclingis restarted. Maire (1981) reported that 27 cycles of liming spentfloat were achieved without destroying the final leather properties.Rao et al. (2003) recycled more than 10 times of the liming spentfloat to save more than 50% water. It is prominent that recycling ofthe liming effluent can save water and can reduce the pollutiontremendously.

Theoretically part of the recycled liming liquid or the corre-sponding washing liquid can be added into the late soaking,because the alkaline remains can accelerate the soaking speed. Thepredeliming float can also be used for liming and reliming to keepthe low content of waste. Here the volume of float is big; there is noneed to recycle several times and adjust the technical recipe.

Fig. 4. Recycle of tannery water waste with circular economy model.

Table 2Comparison of tanning float and pickling float (Ludvik, 2000).

Sample Cr2O3

(%)Neutralsalt (%)

pH Density(kg/m3)

Solid(%)

Temperature(�C)

Tanning float 0.4e1.0 6e10 2.5e4.0 1.06 � 103 0.02e0.20 37e40Pickling float 0 6e10 1.8e2.5 1.06 � 103 0 20e22

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228 225

The effluent of bating contains ammonium salt, calcium salt,enzyme, hydrolyzed protein and epidermis. If it is used for soakingor liming, the enzyme and calcium will impact the quality of thepelts, whereas, the influence is less if used for predeliming,deliming and bating, specially the second or third washing float ofbating containing less enzyme and calcium. Anyhow, when thismethod is applied, the dosage of enzyme can be slightly reduced orkept invariable.

Effluent from tanning can be applied in pickling and tanningagain, which normally has common salt, sulfate, chrome, fat andsuspended solids. Xu et al. (1999) analyzed and compared tanningfloat and pickled float. The main components of both floats aresimilar as shown in Table 2. Generally, the solid and fat of theeffluent must be filtrated by the separate pit. Then, pH of thesystem is reduced by adding sulfuric acid or formic acid (the finalpH of tanning float is 4.0). At last, the effluent from tanning can beincorporated into pickling float after the pelt and salt running10 min in drum.

Table 1The main components of typical soaking and liming effluent (Ludvik, 2000).

Process Salt(kg)

Suspendedsolids(kg)

COD(kg)

BOD(kg)

Total KjeldahlNitrogen (kg)

Sulfate(kg)

Soaking 85e113 11e17 22e33 7e11 1e2 1.0e2.0Liming 6e17 53e97 79e122 28e45 6e8 3.8e8.7

The above figures are based manufacture of 1 � 103 kg cattle hides.

Tanning effluent can be heated up and added at the late tanning.For it has masking effect, the final pH and temperature of tanningfloat can be a little higher than that of the traditional process tomake chrome fixation better. This effluent can be applied inretanning to take the place of chrome powder partly.

The key point of reducing the leather manufacture pollution isto reuse the wastewater, especially for the tannery wastewater(Wang et al., 2006). The above methods can be inferred accordingto the CE model, and tannery should balance its own processes andchoose the best way to reduce the consumption and wastewater.For the chemical complexity in the leather processes, more atten-tion should be paid to the overlap of certain materials such as salt,ammonium and sulfate which can be balanced by the reduction atthe previous stage. In all, the CE model can make the comprehen-sive ecological analysis in leather manufacture.

4.2. Reduction of salt

Salt-based preservation methods are commercially practiced inthe world. The conventional method of preservation employsnearly 40%e50% salt, which is subsequently removed during thesoaking operation. Chlorides in soaking effluents are about85e113 kg (based on 1 � 103 kg raw hides), which is not easilyeliminated with the physical, chemical and biological treatment(JanTiest and Alois, 2005). In China, the dry salt can be shook fromthe raw hides with the tumbler. Although the salt sometimes is toodirty to use, this method can still decrease 8%e10% salt pollution. Infact, the key of salt reduction is to preserve the raw hides. Atpresent, the available method is to add the less salt with biode-gradable biocide. Besides, the raw hide refleshed in the slaughter iscured by brine in which less salt needs. Rao et al. (2009) reportedthat the skins preserved with polyethylene glycol 200 (PEG200)reduced the BOD, COD, Cl� and salinity loads in the soak liquor by75%, 28%, 98%, 93% respectively.

On the other hand, salt also comes from the pickling process. Sothe approach of no salt or less salt in pickling system is either basedon no swelling organic acid or pretannage before tanning.

4.3. Reduction of sulfide and COD

When the discharged wastewater via CE model is reduced asdemonstrated in Section 4.1, the sulfide and COD are also decreased.The analysis of Reduce and the own process is given below on howto reduce the discharge of sulfide and COD.

In traditional process, excessive sulfide is applied to make sureof the complete removal of hair and epidermis. With the CE mode,the dosage of sulfide can be less to 1.3% with very clean pelts.Besides, the enzyme and liming auxiliary is also helpful for thedepilation.

Novel methods have been developed to decrease the effluent ofsulfide and COD, such as the painting for calf, sheep or long hairedgoat skin, the hair-saving system initiated in 1990s, the Sirolimemethod developed in 1981 by CSIRO (Commonwealth Scientific andIndustrial Research Organization) Leather Research Centre(Baumgarter, 2007; Duan, 2000) and so on. Hair-saving system notonly is more ecological but also can increase the leather propertiesand yield. The Sirolime method (Çolak et al., 2005; Cranston et al.,

Table 4The typical effluent components including the followed washing (Ludvik,2000).

Chemicals Load

Sulfide (kg) 0.1e0.3COD (kg/m3) 13e20BOD (kg/m3) 5e9Sulfate (kg) 10e26Total Kjeldahl Nitrogen (TKN) (kg) 3e5NH3eN (kg) 2.6e3.9

The above figures are based manufacture of 1 � 103 kg cattle hides.

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228226

1986a,b) was as the following. Sodium hydrosulfide was impreg-nating the hair root at pH 9e11 to protect the hairs. Then, thehydrosulfide associated with the external part of the hair is lateroxidized with calcium hypochlorite. The remaining hydrosulphidewill be activated by lime and loosen the hair. The float is afterwardrecirculated through the filter to separate the loose hair. Subse-quently, this method has been ameliorated because of the releaserisk of hydrogen sulfide. Reductive and lime are added at beginningof liming for immunization. Sodium hydrosulfide is used as theunhairing agent, and the unhaired pelts are relimed after 3 hfiltration. The advantages of the above modified method are lowcost and suspended processes. However, the process is complexand the insufficient unhairing in batches of hides. The Blair (1986)Hair method was developed in 1985 by Rohm and Haas Co. Ltd incooperation with Eagle Ottawa Leather Co. Ltd. After the immuni-zation of lime, sodium hydrosulphide is incorporated and the hairsgradually are loosened. When the hair loosening is finished, theliquor is discharged and filtered. The subsequent reliming process iscarried out by means of lime, hydrosulphide and the auxiliary. Notall hair is removed for possible over-immunization. Washing withrunning water leads to the excessive water consumption, however,there is no need of recirculation system. The research of BASFreveals that the hair-saving process is more ecological, more helpfulto reduce the amount of sulfide, lime and COD. The data has beenindicated in Table 3.

4.4. Reduction of ammonium salt

The amount of deliming and bating effluents, including washingwaters, fluctuates is about 7e11 m3 (based on 1 �103 kg raw hides)as shown in Table 4. The deliming without ammonium has becomethe trend of cleaner technology (Luo et al., 2007).

Ammonium-free deliming agents are always applied in delim-ing process without ammonium, which are usually based onvarious organic and inorganic acids, carboxylic ether and non-swelling aromatic acids et al. Table 5 displays that NH3eN pollutionin ammonium-free deliming and bating decreases obviously.Besides, carbon dioxide works in the same way. However, a smallamount of ammonium salt has to be incorporated to improve thepenetration. Pure carbon dioxide deliming is only limited on thinpelt or liming split hide. The working place should be well venti-lated to avoid workers’ suffocation of less oxygen. Normally thespecial drum is required; hence, few tanneries adopt this method(UNIDO, 2007).

It can be concluded that when the CE model is applied indeliming and bating, Reduce is still the first guidance to reducepollution load. The span of ammonium deliming to ammonium-free deliming can also be regarded as the gradual process of Reduce.

4.5. Reduction of chrome

Chrome is approximate 2e5 kg (based on 1 �103 kg raw hides)in the chrome tanning effluent. When the CE model is used in thereduction of chrome pollution load, the first step is to Reduce. The

Table 3Comparison of hair-saving and hair destroying system (Ludvik, 2000).

Chemical Hair destroying Hair saving Distinction（%）

COD (kg/m3) 50e60 20e25 59BOD (kg/m3) 30 10e12 63H2S (kg/m3) 4 2 50Total Kjeldahl Nitrogen

(TKN)(kg/m3)5.5 3.5 36

CaO (kg/m3) 15 8 47

decrease of chrome powder not only reduces the pollution, but alsoimproves the rate of the chrome fixation and wetblue yield. Thesecond step is to change the operation conditions. The betterfixation of chrome can be achieved by controlling the float ratio,fixing time, temperature and pH, high exhaustion chrome andmasking agent. The last one is Recycle as explained in Section 4.1.

The CE model can be utilized as both close system and opensystem. One example for chrome recycling system is the chromerecovery from the chrome tanning effluent by the chemical coag-ulation (Song et al., 2004) and the precipitation with alkaline (Muet al., 2003; Esmaeili et al., 2005) and then dissolved by sulfuricacid. Although this method is simple, the cost is relative higher formore alkaline needed. In order to decrease the high cost, somenovel methods have been developed. Kanagara et al. (2008)recovered the chromium present in the spent tan liquor using theneutralized wattle extract. The chrome was recovered and reusedfor tanning the pelt. The wattle extract left in the tanning bath wasreused for post-tanning process as a retanning agent. Katsifas et al.(2004) selected an Aspergillus carbonarius isolate from an estab-lished microbial culture collection to study the biodegradation ofchromium shavings in solid-state fermentation experiments.Approximately 97% liquefaction of the tannery waste was achievedand the liquid obtained from long-term experiments was used torecover chromium. Wang (2006) and his colleagues preparedkeramics with common clay, chrome sludge and alkaline sinterfrom steel factory. Thismethod can be considered as open system. Itis an economic way of digesting solid pollution.

4.6. Reduction of solid waste

1 � 103 kg raw hides generate at least half solid waste in thetannery processes; hence, there is a direct broad prospect to reusethis waste. Recently, many researchers in the world have initiatedcomprehensive works, for example, the fleshing is reused to getgrease and feedstuff, the hair is used tomake brushes, soil regulatorand so on. With the wide scope, more instances can be built up asCE model. The natural fats obtained in fleshing can be reused asbiodiesel (Çolak et al., 2005) and leather fatliquoring agent (Santosand Gutterres, 2007).

The blue shavings and trimmings canbeusedas the rawmaterialsof the retanning agents. The dehydrated sludge can be used asfertilizer and the waste liming pelt scraps as pet chews after treat-ment (Eleanor et al.,1996; Stockman,1996; Cheng et al., 2002;Wanget al., 2002a,b; Manzo and Fedele, 1994) and finishing agents (Muet al., 2002; Mu, 2001). Oliveira and colleagues used the chro-mium-containing solid waste as the low cost adsorbent materials

Table 5NH3eN Comparison of ammonium deliming and ammonium-free deliming (Ludvik,2000).

Process NH3eN (kg/m3) Load (kg)

Ammonium deliming 2170 2.6Ammonium-free deliming 85 0.1

The above figures are based manufacture of 1 � 103 kg cattle hides.

Fig. 6. The chrome liquor recycle system.

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228 227

with the high adsorption ability on removing dyes (Oliveira et al.,2007) and the fertilizer with slow liberation (Nogueira et al., 2010).Recently, Zhaofu Tannery in Guangdong, China hasmade the leathersolidwaste into the retanningfilling agents successfully. This processis viewed as the close cycle of transforming the leather solid wasteinto leather materials. Zhaofu Tannery has disposed 12.4 � 105 kgleatherwaste solid from16th, November, 2008 to 30th, April, 2009 toobtain3.5�105kgretanningfillingagents (http://www.022net.com/2009/7-28/463263382831076.html). Besides, the shavings fromchromium-tanned leather can beused as the rawmaterial to ceramictile industry (Basegio et al., 2005).

4.7. Ecological utilization of Circular Economy model in HebeiDongming Bright Cattle Co. Ltd in China (http://info.leather.hc360.com/2009/04/17081331955-2.shtml)

Dongming Bright Cattle Co. Ltd is located in Hebei province inthe north China. The company has a total area of 77,372 m2 and 470employees. The total investment in fixed assets for DongmingBright Cattle Co. Ltd is 1.5 billion (RMB) and its output is 1 millioncattle hides per year. As the biggest leather production base inHebei province, Dongming Bright Cattle Co. Ltd inputs the hugeman power andmaterial resources to build up the effective ecologicleather production process by adopting CE model, with the intro-duction of 20 overloading drums and the corresponding water-saving recycle process at the price of 904 million RMB.

An overloading drum can bear 2.5 times more hides than theconventional drum of the same size. For its construction, the waterfloat is alwayshalf lower than thenormal in theproductionprocesses.And for the processes’ properties, the overloading drums arespecialized for the soaking and liming processes, where are locatedthe biggest contribution of waste effluent. Besides these 20 special-ized facilities, a hair-saving liming processes with liming effluentrecycling system as demonstrated in the liming part of Section 4.1 isconducted in the production site. Fig. 5 displays the actual limingliquor treatment flow in the recycle system with the overloadingdrums in Dongming. Based on the difference between the traditionalprocess and this one, Dongming Bright Cattle Co. Ltd saves 1�105 kgfreshwater and 1.5�105 kwelectricity power, decreases 1.3�106 kgwastewater annually, and as reported, Dongming saves 23.5�104 kgsodium sulfide, 8.4 � 105 kg lime annually. At the same time, for itsdistinctive contributiontotheecology,Dongminghasbuiltup itsownreputation of cleaner production corporation. These processes havechanged fromthe traditionalmodel (high resource consumption-lowefficient production-high discharge) to the updated model (lowresourceconsumption-highefficientproduction-lowdischarge).And

Fig. 5. The liming liquor flow in the cycle system with the overloading drums.

these processes, not isolated anymore, are interrelated to each othersto have optimal efficiency of raw material or energy by mimickingecosystem.

Additionally, the saved hair is the by-product of hair-savingliming process. In Dongming, the annually recycled 6� 105 kg hairsare treated as organic fertilizer. The eco-efficiency is obvious sinceon one side, it reduces the solid waste discharged to environment,on the other side; it works as nutrition supplier to flowers andtrees. This case demonstrates that to support the resource optimi-zation a broader system could be involved encompassing networksor chains of firms, eco-industrial parks, and regional infrastructure.

The chrome liquor recycling system is shown in Fig. 6. Incontrast to the traditional pickling and chroming method, inDongming 25% salt can be reduced with 30.8% chrome liquorreused which is completely possible through the chrome recyclingmodel and the technical support. It is estimated that 17.6 � 104 kgcommon salt and 47.1 � 104 kg chrome float should be reducedevery year. The implementing of CE model saves the economic costof 3.5 million RMB for Dongming Bright Cattle Co. Ltd annually. Inall, Dongming Bright Cattle Co. Ltd has had the successes inimplementing and promoting the CE model.

All such figures are going without saying that this case, as anexample of CE model, reduces the consumption of the resourcesand generate less pollution compared to the existing way ofproduction activities. This case can also be viewed as an example ofIE, since that there are multiple coupling processes based on themetabolism system with high efficient, harmonious and sustain-able use of resource.

5. Conclusions

The leather industry in the world will exist and keep developingat a rather stable rate, which is attributed to the increase of theglobal livestock production (Global Livestock Production andHealth Atlas). However, the key issue of leather industry sustain-able development is to solve the conflict between its manufactureand pollution. This CE model may be easy to be implemented forthe leather industry to alleviate the tannery wastes. Reduce, Reuse,Recycle and Recover of the whole tannery effluents have beendiscussed in detail according to the various wastes.

The case of Dongming Bright Cattle Co. Ltd in China with a CEmodel shows that there is a great potential in saving economic costand reducing the environment pollution, as indicated by decreasingconsumption of fresh water and energy and also in reducing theamount of producedwaste and pollutants. However, challenges stillexist for the whole leather industry due to the economy restrictionand the strategies limitation. CEmodel development experiences inDongming Bright Cattle Co. Ltd can be viewed as an example of IEand as an example of other leather tannery companies searching forcleaner and sustainable production. In the future, each leathertannery company may develop its own CE processes according tothe local realities based on this CEmodel. CEmodel will become thenecessary measurement for the sustained development of theleather industry.

J. Hu et al. / Journal of Cleaner Production 19 (2011) 221e228228

Acknowledgements

Financial supports of this article from the Shanghai ChenguangFoundation (ItemNo.: 10CG60) and Science Foundation of ShanghaiInstitute of Technology (Item No.: YJ2009-26) are appreciated.

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