characterization of leather industry wastes

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Original Research

Polish J. of Environ. Stud. Vol. 16, No. 6 (2007),

Introduction

The principal aim of the leather industry, which plays a

siict roe i tod’s ob ecoom, is to trsformim ides/skis ito psic d cemic stbemteri b subjecti tem to cemic d mecicsequeti processes, d terefore to obti products formeeting various needs of people. The leather industry gen-

er uses ides d skis s r mteris, ic re te by-products of meat and meat products industry. In this

respect, the leather industry could have easily been distin-

guished as an environmentally friendly industry, since it processes ste products from met productio [1]. ho-

ever, the leather industry has commonly been associated

with high pollution due to the bad smell, organic wastes

and high water consumption caused during traditional

mufcturi processes [2]. Differet forms of ste iquit d qutit, ic emere duri te trsfor -mtio of ides d skis ito eters i tousds ofleather factories, from primitive to modern all around the

world, have negative impacts on the environment.

Although the characterization of solid wastes from the

tanning industry is well documented, our study investi-

gates the properties of the solid wastes generated from dif-

feret tpes of eter – produci teries, i.e. rmet,soe upper, soe, etc. as it is ko, produci differettpes of eter requires differet tpes of processes dcemic use. Cosequet, eter stes eertedfrom each type of leather and process have different char-

acteristics. According to us, for the utilization of these

stes i vrious eds, vi more specic iformtioabout their characteristics has great importance. In this di-

rection, in this research an overview of leather processing

is mentioned and wastes coming out of various factories

and process steps are characterized with the aim of obtain-

ing data for evaluating them.According to the data received from the studies of sev-

er resercers, pproximte 200 k of eter is mu-

fctured from 1 toe of et-sted ide [1-3]. Tis moutcostitutes bout 20% of ride eit. More t 600k of soid ste is eerted duri te trsformtio ofrawhide into leather. That is to say, solid wastes contain-

i protei d ft tt costitute more t 60% of r-

hide weight are disposed to the environment by leather

fctories itout turi tem to ood use (Tbe 1).I oter ords, besides te 30-35m3 waste water dis-

posed to eviromet duri te processi of ever 1 to

of rawhide in world leather industry, the data from FAOreves tt pproximte 8.5 miio tos of soid steis eerted duri te productio of 11 miio tos ofride processed i te ord [4].*Correspodi utor; e-mi: [email protected]

Characterization of Leather Industry Wastes

H. Ozgunay*, S. Colak, M.M. Mutlu, F. Akyuz

Deprtmet of leter Eieeri, Fcut of Eieeri, Ee Uiversit, 35100 Borov, Imir, Turke

Received: November 14, 2006 Accepted: June 13, 2007

Abstract

In this research samples from solid wastes coming out from various process steps during manufacturing

of rmet seep skis, soe upper ot skis, soe upper ides d soe eters ve bee coected. Tese

samples have been classified among themselves and their characteristics have been determined by various

chemical analysis. By characterization of solid wastes which state problems for the environment and costs

for treatment; data have been obtained which can be used for new management and evaluation methods.

Keywords: eter, ide, ski, soid ste, eviromet

867-873



Ozgunay H. et al.868

It is possible to divide leather industry processes of

transforming rawhide into leather into four main stages:

i. Beamhouse processes:

Te coserved ides re rst subjected to trim-

ming process for removing the unwanted parts, and

then they are soaked to restore the lost water and to

remove substces ike dirt, bood d coservtio

salt. After the wetted hides are eshed to remove theexcess es d ft deri to te ide (poder -mis), te re treted it itese ki soutio ofime (C(Oh)

2) d sodium supide (n

2S) to esure

ir d oo remov (unhairing process). lter tehides are swelled up in liming process by immersing

tem i stro kie bt so s to ope up tecollagen structure. The hides may be treated with a

secod esi process fter imi i order to cete es. at tis ste, ides re treted it splitting

process and split into two or three layers. Deliming is

te performed to decrese te ph eve i order to

remove te ime d to mke te ide more receptiveto the chemicals that will be used in further stages.

Through bating process, ides re exposed to e-

matic effect for both opening up the structures, and the

removal of unwanted proteins from the hide. Follow-

ing the bating process, a degreasing process is applied

to ides for removi te excess tur ft i teirstructure and providing a homogeneous distribution of

the fat in it.

ii. Ti Processes: Te ides t tis ste re rst treted it pickle pro-

cess in a solution composed of salt and acids so as to

obtain a homogeneous distribution of tanning materi-

als through the cut. After the hides are conditioned as

above, the tanning process is applied with various tan-

i mteris (mteris be to form stbe bods itcoe) i order to provide te eter it stbeform and high thermal stability. Tanning materials such

as vegetable tannins, mineral tanning materials and

sts (stetic oric ti mteris) re usedin tannage. Among mineral tanning materials, chrome

is the most widely used in leather production due to itsuique fetures tt it ives to te eter. aumiiumand vegetable tanning materials are also widely used in

leather production.

Before the leathers are treated with further processes,

the setting out and samming process is applied, and

shaving is doe to obti te desired tickess of teleather.

iii. Post-Ti Processes: Te ext step for te eters, ic re ted d

stdrdied to desired tickess, is retannage pro-

cess with various retanning agents improving the re-

quested crcteristics of products. I tis process,structural differences within leathers are compensated

to obtain uniform structure. The Fatliquoring process

is ppied b usi combitio of vrious ftiquor -ing agents in order to allow the leather to be more

supple and softer. In the dyeing process leathers are

dyed to the desired color. After this stage, leathers are

ed d dried, d te re prepred for te -

ishing process through certain mechanical operations.

The unwanted parts are trimmed and removed.

iv. Fiisi Processes: after te eters re ftiquored d ded fooi

the tanning process, they are processed with a series

of coatings on the surface in order to improve theirresistance and produce appealing and uniform surface

effects. After this process, leathers are trimmed for a

form d set to cofectio.

Soid stes eerted b te eter idustr i tesestes of processes m be cssied s foos: i. stes from uted ides/skis (trimmis, es-

i stes) ii. stes from ted eter (svi stes, buf

dust)iii. stes from ded d ised eter (trimmis

from eter)Dt obtied from reserc reves tt 80% of soidwastes are generated during pre-tanning processes, while

20% of te stes re cused b post-ti processes

Tbe 1: Estimted mout of soid (protei, ted d u-

ted) ste duri te processi of 1 to of sted ides c-

cording to various authors

Püteer aexder Buj

Uted ste:shavings

subepidermal Tissue

trimmings

530 k135 k

120 k70-230 k

100 k300k

Tanned Waste:

shavings

split

145 k 100 k115

99 k107

Ded d ised ste:shavings

uff 10 k 32 k

2 k10 k1 k

Total 870 k 439-599 k 637 k

Fi. 1. amouts of eter idustr r mteri iput d soid

waste output.




45-59% i pre-esi ste, 57-83% i ime es-

i ste, 45-66% i svi ste, 7-14% i bufste, d 6-9% i eter stes. Sempere et . [9]ve observed tt ter cotet of eter ste (18-25%) is oer t te ter cotet of svi ste(45-57%).

Te obtied dt reve tt esi d sviwastes include higher amounts of water in comparison

to other waste types. This result is due to the fact thatesi d svi stes re eerted duri et-

er process steps called beamhouse processes, in which

leathers are processed in watery environments. Water

cotet of soid stes ike buf d trimmi relower, since they are generated during the stages of dry

processes.

wter cotet of soid stes differs to ret extetin accordance with how and where they are collected,

storage conditions, and climate. Yet there is always an ob-

vious water content difference between the wastes gener-

ated during wet and dry processes. Water content of solid

stes is of ret siicce t te time of store duse.

Due to te i mout of ter i eter stes, ortur fctors ike ri or so, ifusio of te cemi-

cals in leather waste into soil and surface/ground waters

causes the deterioration of the natural structures of these

receiver environments. Especially in the case of wastes

including chrome, researchers have reported the infusion

of crome ito pts d roud ters [9].

ph

It has been observed that solid wastes show similari-

ties i pre it te process stes discosi te phvues of soid stes, d te ph vues t ic tese

processes are carried out; and it was found that liming

esi ste s te iest ph vue, sice te imi process is doe t roud ph 11-12.

Acid-base reactions are among the most important

mtters rerdi te eviromet. Most of te iviorisms re ver sesitive to eviromet ph. a-

oter situtio is tt, e ph is forced to extreme im-

its, chemical balance reactions slide to the left or right,

causing the occurrence of undesired sediments or gases.hece, i order to protect te curret ecosstem, stessoud be subjected to eutritio process before teare disposed to the environment.

Tbe 2. Me vues of some crcteristics of eter idustr ste.

Type of WasteWater Content

% ph

Ft&Ois%

Nitrogen

%St%

Supur SO2

(ppm)Coric Vue

kc/k

A1

58.99 7.29 58.5 14.7 1.41 n.d. 7953

B1

44.40 7.23 53.5 5.9 1.71 n.d. 7375

C1

45.77 7.4 56 34.6 2.56 n.d. 5345

D1

45.77 7.44 56 17.1 2.52 n.d. 5642

A2

61.65 12.37 53 13.1 1.77 439 4852

B2

83.72 10.06 25 25 0.87 243 4916

C2

57.13 12.43 6 31.3 2.82 65 5753

D2

57.13 12.49 7 18.2 2.86 n.d. 5146

A3

66.01 3.93 2.4 60.3 4.65 n.d. 3884

B3

63.99 4.28 0.85 61.2 3.95 n.d. 3912

C3

46.61 4.17 2.15 64.1 4.68 n.d. 4354

D3

45.86 5.24 2.1 31.7 1.72 n.d. 4552

A4

14.58 4.3 4.05 35.4 2.00 n.d. 4820

B4

8.57 5.81 3.5 46.5 1.60 n.d. 4902

C4

6.97 6.01 3.9 47.7 1.66 n.d. 4056

D4

9.26 4.26 4.1 26.4 1.37 n.d. 4544

A5

7.24 5.47 6.95 49.4 1.49 n.d. 4685

B5

6.39 4.46 4.35 48.6 1.48 n.d. 4929

C5 8.83 4.75 7.05 46.7 2.21 n.d. 4744

D5

8.83 4 4.25 28.7 2.08 n.d. 4541



Characterization of Leather... 871

Te amout of Substces (Fts d OterSoubes) Soube i Dicoromete

Uess te ft i ride structure is removed, it f -fects other processes in a negative way by prohibiting

the penetration of chemicals into the hide in further pro-cesses, and may also cause a strong smell, an increase in

micro-orism ctivit d defects ike spe o eters.For this reason, vast amounts of fat in hides are removed

before ti b ppi deresi process. Biekie-

ic [10] oted tt ft cotet vries betee 0.5% d4% i ctte d orse ides, 3% d 30% i seep ski,4% d 40% i pi ski, d 3% d 10% i ot skiover dry weights.

Another fat source in solid wastes is the natural or

stetic fts used i te ftiquori process i orderto provide te eter it fetures ike softess, estic-

it d resistce, d to o te eter bers to sideeasily over one another according to the leather type and

purpose of use. The fat content of leathers consists of the

remaining natural fat after degreasing process, and the fat

used i ftiquori process. Due to tis reso, differetfat proportions may be detected in leather wastes.

I te reserc, it s bee observed tt pre-esid ime esi stes from te processes before de-

greasing include higher amounts of fat compared to other

ste smpes (40-70%). I dditio, it soud be kept imid tt stes ere eerted t te ed of te es -

ing process that was applied to remove the hypodermis

layer of the hide, which is the layer including the highest

mout of ft. It soud so be tke ito cosidertiott es d ft ers eft o ides m differ ret,depedi o suter d i teciques, ic iturn directly affects the fat amount in waste. This high

mout of ft i esi ste m be evuted i differ -et eds suc s te cemic idustr, sop productio,

biodiese productio, d te productio of ftiquors [7].Te ft obtied from ime esi ste is eer re-

rded to be of o quit due to its dirt coour d bdsmell resulting from sulphide contact.

Nitrogen Amount in Wastes

Determitio of itroe i soid stes ives idea about proteins as the main component of leather,

and therefore about the effect of leather processes on pro-

teins.

The results obtained from nitrogen determination

sis coducted it te Kjed metod i stesmpes ve reveed tt esi stes it 6-34%nitrogen have the lowest amount of nitrogen, and there-

fore the minimum protein content. As mentioned before,

tis resut stems from te fct tt esi stes re te

ones generated by the removal of a hypodermis layer,which is rich in fat and poor in protein.

Svi stes icude te iest mout of itroe(64%). Crome i tese svi stes m be removed

to ret extet b treti te smpes it ki orwith the help of enzymes, and thus protein hydrolysates

itout crome m be obtied (<5ppm). Terefore, itis possible to put shaving wastes into commercial use due

to its wide area of use such as leatherboard, fertilizer or

droste productio [11, 12].we oter dt ere exmied, itroe cotet of

te stes from soe eter mesuri 26-31% s foudto be lower than the nitrogen contents of other waste types.

Sice te rte of veetbe ti substce i te ste(popeoic substce) icresed, te itroe moutdetected in leather decreased accordingly.

Sodium Coride Cotet

we te st cotets of soid stes ere exmied,

it was found that salt proportions in most samples vary be-tee 1% d 2.5%. as mtter of fct, it is remrkbett st cotets of svi stes from ski tpesare higher than the average values of other samples, and

this difference is thought to stem from the high rate of

ki sts used especi i bsictio t te ed of techrome tanning process; since this parallelism detected in

shaving wastes is not observed in the shaving wastes from

sole leather treated with vegetable tanning process.

The high content of salt in solid wastes causes an in-

crease in the salt amount of the soil where these wastes

re stored. Soube sts ve etive effects o ptrot, becuse te itke of utritio eemets bthe plant is prohibited due to ion competition when the

soil contains high amounts of cation and anions. This salt

dme emeres becuse of te isufciec of utritio-

al elements. Additionally, high salinity or total dissolved

salts in water causes high osmotic pressure, which results

in reduced water availability to plants and retarded plant

growth of crops which are not salt tolerant [13].

Supide Cotet

As mentioned before, in beamhouse processes, ac-

cording to the type of desired leather products, hides/skis re treted it itese ki soutio d so -

dium sulphide for hair and wool removal and opening up

the structure. In this step, disulphide bonds are destroyed

b reductio uder ki coditios. Terefore, s is soseen from the results, the wastes coming out from these

stages are distinguished from others by their high sulphide

content. The highest amount of sulphide was detected in

seepskis (439 ppm), becuse tese r mteris reeer used i productio of rmet-ike soft etertpes d i order to obti required properties, itesiveimi d uiri is ppied. got skis d ides used

for production of shoe upper leathers are generally treatedit ess ime d supide i order to obti rmer et-

ers, and so wastes occurring at these stages have less sul-

phide content.




Thermal Values

As presented in the graphics, due to their high content

of ft, esi stes it vere of 5872 kc/kthermal value have higher thermal values than that of oth-

er stes it vere of 4493 kc/k.The thermal values belonging to some urban wastes

ere determied to be 2770 d 4450 kc/k i pper,6660-8885 kc/k i pstic, 3600-4440 kc/k i tex-

tie, 4990-6660 kc/k i rubber, d 3600-4730 kc/ki eter [14]. I some cses, eter stes re exter -mited b iciertio due to teir i coric vues(4500-5000 kc/k) [15]. Term tretmet of eterscrp must be justied ot o b its i coric vue,

but b tki ito ccout s muc s possibe of te co-

sequeces of it, me (i) poutts d teir eves ite reesed sses; (ii) crcteristics of te ses d

fctors tt iuece ces i te cromium oxidtiostate during the burning process as well as in some of the

further ash treatment options. These considerations must

s be directed to usefu eds [16].

Determitio of Cr, Fe, n, C Ios i leterWastes

Some Io mouts detected i soid stes eerted by the leather industry are introduced in the table below.

As displayed in the table, chrome was detected to be

high in waste samples which are treated with chrome in

the tanning process. The indicated Cr +3 content is the re-

sult of chrome used in tanning.

Chromium traces found in sole leather shaving and

buf stes ere ssocited it te cotmitioof wastes, since chrome is not used as the main tanning

substance in sole leather production. An increase was

observed in chrome contents of sole leather wastes, and

therefore it was considered that waste samples treated

it crome rete i te ste for specic purpose during sole leather production were evaluated

among the samples. Naturally, Cr ion was not detected in

esi stes.

Cromium s to importt oxidtio sttes: triv-et (Cr +3) d exvet (Cr +6). Trivet cromium is ofo toxicit d is esseti trce io ecessr for sev-

er biooic ctivities, eres exvet cromium isof i toxicit [17, 18].Ter stes orm cotio trivet cromium [10, 19, 20]. Te productio ofcromium-cotii soid stes (icudi cromesvis) i ter s bee recoied s probemfor many years but recently pressure from environmental

authorities has given the problem increasing urgency. As a

resut, m scietic roups ve orieted teir resercto d process to recce tese stes. Te cemic

compositio of crome svis mke tem suitbe for processing to recover their constituents but the economics

of the process is very important for industrial implemen-

tation [21]

O te oter d, bout 90% of ides/skis i teworld are still tanned with chrome, because other tanning

materials fail to give the leather a high hydrothermal sta-

bility and other use properties that chrome provides.

Iron amounts in waste are generally not very high,

and vary according to the iron content of the water usedin processing, and the process after which the waste is

eerted. For exmpe, te iro dust pperi durite srpei of kives used i te esi process toremove te es side ced podermis er, or te irodust eerti from buf pper duri te buf pro-

cess may cause changes in determined values.

I te resuts coceri ccium (C) cotet, tei mout of ccium determied especi i esiwastes is caused by the lime used in the liming process

applied for opening up the structure and conveying ad-

ditional functional groups.

Sodium cotet i te stes c be formed frommany sources. It can either originated from sodium chlo-

ride or sodium sulphate. The amount of salts used in the

productio of vrious kids of eter tpes d vrious processes differs i ide re. For exmpe, ti procesess crried out t o ph vues or stro cidic

Tbe 3. Me Vues of Cr, Fe, n d C Cotets of leter

Idustr wstes (ppm).

Type of Waste Cr Fe Na Ca

A1 n.d. 1206 27496 6972B

1n.d. 667 4014 19310

C1

n.d. 915 14612 12185

D1

n.d. 1407 27217 16424

A2

n.d. 894 9000 76000

B2

n.d. 1835 15000 87000

C2

n.d. 4272 45384 11799

D2

n.d. 626 29679 42399

A3

14500 11 15000 700

B3 14493 27 10243 745

C3

17943 282 14234 711

D3

43 378 5919 1566

A4

11783 1467 49350 4632

B4

23747 77 707 1516

C4

15000 521 11000 6200

D4

28 992 14894 2780

A5

14989 34 2100 900

B5

18360 123 1504 701

C5

13530 29 997 897

D5

1492 452 19083 1094



Characterization of Leather... 873

coditios, require picki d more buffer sts. Simi-r, i eutritio d bsictio procceses vri-ous n-bsed buf sts d ki sts re so used.These salts cannot be completely washed out and remain

i eter. hi cocetrtios of sodium ios i irri-

tion water adversely affect soil structure by causing dis- persio of c. Probems it soi permebiit c occurdepending on sodium, calcium and magnesium ion con-

cetrtios i soi [13].

Conclusion

Leather products are manufactured using various

processes and chemicals which may show variations de-

pending on the desired the leather characteristics. Con-

sidering this particular fact about the leather industry, we

have carried out this study on the solid wastes of differenttanneries that produce leather for different purposes and

therefore use various processes and chemicals. The results

of this study have revealed that the leather industry gener-

ates waste with different characteristics according to the

process step at which it is generated. The obtained data

cer reves tt te cotets (bot protei d ft) ofmost te esi, svi d trimmi stes, etc.,which constitute a great amount of the generated wastes

i eer, m be reused i oter differet eds for eco-

omic purposes. For exmpe, pre-esi stes c beused i te productio of ftiquori ois d biodiese,imed esis c be used i productio of mete s,grease and protein recovery and fertilizer after compost-

ing, shaving wastes can be used in production of leather-

bord or reti et d etie fter eme/kidigestion and also shavings and trimmings can be used in

the production of activated carbon, etc.

Cosequet, i order to determie te most ppro-

priate method for reusing and disposing of these wastes, it

is i importt to cquire te iformtio cocerithe process steps, during which these wastes are gener-

ated, the target product desired to be produced through

these processes, and the characteristics of wastes depen-

dent on these factors.

References

1. langMaIER F., KOlOzMIK K., SUKOP S., MlaDEK

M. Products of Emtic Decompositio of Crome-

Ted leter wste. JSlTC. 83 (4), 187, 1999.

2. TaylOR M.M., CaBEza l.F., DIMaIO g.l., BROwn E.M.,

MaRMER w.n., CaRRIO R., CElMa P.J., COT J., Process-

i of leter wste: Piot Sce Studies o Crome Svis.

Prt I. Isotio d Crcteritio of Protei Products d

Seprtio of Crome Cke. JalCa. 93 (3), 61, 1998.

3. VEEgER l. Ecooic Procedure to Sove te Terwste Probems. JalCa. 88 (9), 326, 1993.

4. FaO. Sttistics. ttp://fostt.fo.or/fostt, (Ju 20,

2004)

5. PUnTEnER a. Te Ecooic Cee of Produci

Leather. JALCA. 90 (7), 206, 1995.

6. RaghaVa RaO J., ChanDRaBaBU n.K., MURalID-

haRan C., UnnI naIR B., RaO P.g., RaMaSaMI T.Recouping the Wastewater: A Way Forward for Cleaner

leter Processi. Jour of Ceer Productio. 11, 591,

2003.

7. COlaK S., zEngIn g., OzgUnay h., SaRIKahya h.,

SaRI O., yUCEER l. Utiistio of leter Idustr Pre-

esis i Biodiese Productio. JalCa. 100 (3), 4, 137,

2005.

8. Societ of leter Tecooists d Cemists, Ofci

Metods of asis. 1996.

9. SEMPERE J.F., MaRTInEz M.l.B., MOnTESInOS R.F.,

lIllO M.C.S. Crcteritio of Ter wstes. Com-

priso of tree ecbiit tests. Jour of hrdous M-terials. 54, 31, 1997.

10. BIEnKIEwICz K. Psic Cemistr of leter Mki.

R.E. Krieer Pubisi Co. Forid, 1983.

11. gISh a.J. leterbord, prctic use of ter off.

JALCA. 95 (2), 43, 2000.

12. TaylOR M., DIEFEnDORF E.J. et . Extrctio of Vue

Added Byproducts from the Treatment of Chromium Con-

tii Coeous leter Idustr wste. JSlTC. 81, 5,

1997.

13. MOnEy C.a. addressi Siit i Ter Efuets

d Uses For ld Irritio i austri d Idi. word

leter. Februr/Mrc, 22, 2005.

14. TOPRaK h. Kti atik Topm, Tşim ve Bertrf Sistem-

erii Eiiemesi ve Ekoomisi, D.E.Ü. Müedisik

Fkütesi yiri no:265, Izmir, 1998

15. alMEIDa M.F., FERREIRa M.J., aus spectos de ici-

erco de residuos de couro curtidos o cromio. 5 th Conferen-

ci ncio sobre Qidde do ambite. 2, 1155, 1996.

16. FERREIRa M.J., XaRa E. et . Usi ases from Ici-

ertio of Cromium Supte Ted leter Scrp. Prt

I: Crcteritio of ases d Cromium Extrctio.

JSlTC. 84, 271, 2000.

17. Committee o Biooic Effects of atmosperic Poutts,

“Cromium”. ntio acdem of Scieces. wsito,

D.C., 1974.18. Smposium o Cromium i nutritio d Metboism,

“Cromium i nutritio d Metboism”. 2, D. Spcott

d J. hubert, Eds., Esevier, amsterdm, 1979.

19. PRaSaD B.g.S. JalCa., Tretmet d Dispos of wste

wter for Ter Processi wet-bues to Suede, 86, 87,

1991.

20. alEXanDER K.T.w., CORnIng D.R., CORy n.J. et al.,

Eviromet d Sfet Issues - Ce Tecoo ad

Eviromet auditi, JSlTC. 76, 17, 1992.

21. CaBEza l.F., TaylOR M.M. et . Tretmet of Seep -

ski Crome Svis. Isotio of hi Vue Protei

Products d Reuse of Cromium i te Ti Process.JALCA. 94, 268, 1999.

characterization of leather industry wastes

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