A case
study on disposal and management system of solid wastes generated from Tannery Industrial
Estate Dhaka (TIED)
Introduction
Leather
is a stabilized and imperishable natural fabric of fine texture obtained from
raw (green) or preserved (Salted) hides and skins of animals by tanning through
involvement of both mechanical and chemical operations 1. The conversion of animal
outer coverings into leather is practiced by the primitive people from ancient
time, which is now one of the most prime-concerned global industries 2. The
leather industry, well known as user of natural resources is always not only
given priority for its economic dominance but also for environmental influence
as it generates pollutant wastes having hazardous impact on environmental
degradation. For this, the leather industry is now introduced as highly
potential polluter industry unless proper disposal and treatment of generated
wastes is performed 3. The wastes generated by the tanneries are classified
into three groups such as solid, liquid and gaseous in nature and are enlisted
in the figure I 4, 5.
Figure
I: Types of wastes generated from tanneries during leather processing 5
In
the conversion of 1 ton wet salted hides, 500 kg of different chemicals, 40 of water (process and technical water) and
2600-11700 kWh energy is consumed but only 200-250 kg of finished leather
(grain and embossed split) is achieved containing only 72 kg chemicals inside
which is only 25.5% of the total raw materials and discharge approximate 600 kg
of waste in different forms 3, 6. The tanneries generate around 6 million
tons of solid waste as trimmings (both tanned and un-tanned), fleshing, splits,
shaving & buffing dust and sludge (both chrome contained and non-chrome) at
an average of 80% in leather processing per annum 7, 8, 9. During beam house
and post tanning operation, most of the solid wastes (trimmings, fleshing,
splits and shaving dust) are generated, containing small amount of (2-6% (w/w))
non-chrome mineral substance usually dependable on quality of hides/skins,
tanning technique and condition process in chemical characteristics. Moreover,
useless splits, shaving dust and unnecessary cuttings carry 3-6% (w/w) of fat
and about 15% (w/w) of mineral components, including 3.5%-4.5% (w/w) of
chromium as generated
from tanned leather. Sludge from wastewater treatment plant generally bears
water (up to 65% (w/w)), organic materials (30% (w/w)) and chromium (iii) compounds
(approximately 2.5% (w/w)) 9.These solid wastes might have limited
implementation but possess serious environmental problem without safe disposal
and treatment 10. Though developed countries are now shifting away from this
sector due to high labor cost and environmental risks, leather processing is
still an unavoidable source of earning foreign money and export trade for many
developing and under-developed countries 11. In Bangladesh, the leather
industry is relatively an older industry with an age-old tradition of over
seven decades has significant involvement of producing such leather, recognized
for its superior grain pattern and strong fiber strength worldwide since 1940
12. According to the annual report of Bangladesh Economic Review of 2017,
leather sector (combining leather industry, footwear and leather products
industries) is ranked second in terms of earning foreign exchange just after
readymade garments and around 1234 million$ is achieved from this sector in fiscal
year 2016-17 13, 14. To keep this momentum steady, the leather industries
situated in the capital’s Hazaribagh area is shifting to Harindhara village of
Hemayetpur Thana under Savar Upazilla over 200 acres land and facilitated with
central dumping yard, sludge power generating system (SPGS) and Central Effluent
Treatment Plant (CETP) which better known as Tannery Industrial Estate Dhaka (TIED)
or partially as Savar Leather Park for the purpose of eco-friendly production
from April 8, 2017 15.
Figure II: Map of Tannery Industrial Estate
at Savar 16
The
tanneries how maintain the generated solid wastes with proper utilization of
treatment system to reduce environmental risk at newly shifted area of Savar
Leather Park are the highlights of this study by an application of
questionnaire and focused group discussions.
Literature Review
The
raw hides and skins, used as the raw material of leather industry is mainly
composition of protein and fat containing amount of 10.5% (w/w) of each groups
and 60% moisture content and high water (both free and bound) 9. Collagen, a
structural protein is presented largely among different types of proteins (collagen, elastin, keratin,
glycoprotein, albumins and globulins)
and accountable to form leather associated with tanning materials 17. During
leather processing the solid waste generates mostly in beam house 80%, tanning
19% and finishing 1 % 18. The nature and amount of solid waste
originated from leather processing of one ton hides and skins are listed in
table I 10.
Table
I: Quantity of generated solid wastes in processing 1 tons of raw hides and
skins 10
Sl.
No.
Name
of solid waste
Quantity
(in kg)
1
Salt from handshaking
80
2
Salt from solar pans (not realized)
220
3
Hair
100
4
Raw hide cutting
40
5
Lime sludge
60
6
Fleshing
120
7
Wet blue trimming (grain splits)
30
8
Chrome splitting
65
9
Chrome shaving dust
95
10
Buffing dust
65
11
Dyed trimming
35
12
Dry sludge from ETP
125
The generated solid wastes of substantial amount from tanneries were dumped
openly at the roadside when the tanneries in Bangladesh were located in the
capital’s Hazaribagh area that caused hazard both in human health and discomfort
in living condition, results environmental calamities 19, 20.
Research Methodology
Study site and population
The study was conducted at Tannery Industrial Estate Dhaka which is located
at Harindhara village of Hemayetpur Thana under Savar
Upazilla of the capital, where 155 tanneries are shifting from capital’s Hazaribagh
Thana and 92 tanneries are running their production. Voluntary participation of
leather technologists of 12 tanneries was included in the study.
Study design and sampling
A cross sectional study was carried
out to design the study frame work. A pilot study was done before sampling and
questionnaire preparation. The tanneries used as sample in the study were
selected by using random sampling method.
Figure III: Conceptual
framework of the study
Find out solid wastes &
effluents
Determine
waste generating source & generation rate
Characterize solid wastes
Dumping
wastes Renewable wastes
Direct dumping Treated dumping Suitable by-products
Treatment cost Treated product’s cost
a)
Compare
both costs a)
Comparison of both costs
b)
Environmental
effects b) Influence on economic benefit
a)
Quality
assessment of dumping process
b)
Further
recommendation for better tannery
solid waste management system
Data collection
A standardized
structured open-ended questionnaire was used for the data collection. The
questionnaire was prepared in English and asked directly translating into
Bengali and applied on December 6, 2017 to December 18, 2017. A skilled data
collection team of three members collected the listed data of questionnaire
using face to face interview technique. Permission from the industry authority
and verbal consent from the leather technologists of tanneries were taken in
advance. Respondents had complete liberty not to response to any of the
questions and leave any time during the study. The interviewer-administered
questionnaire included the general information of the tannery (number of
workers, annual turnover, tanning methods and final products), disposal of solid
waste (generation of wastes, kinds of generated wastes, utilization and
recycling of waste, final destination of sludge and other solid waste). Information
on quality assessment & using of dumping yard was collected by approaching
focus group discussion method.
Data analysis
To achieve the objective of the study, qualitative method was approached
with utilization of descriptive analysis, comparative analysis, and cost
benefit analytical tools. In descriptive analysis, the general information of
the tanneries like ownership, workforce, annual turnover, application of
tanning methods, production type and capacity were included that highlighted a
general overview of tanning, leather production and involvement of people in
leather sector of Bangladesh.
In comparative analysis, the quantity of generated solid wastes was
compared with the quantity of solid wastes of table I highlighted in literature
review part by converting the values evolving in processing 100 kg hides and
skins. Moreover, treatment technologies of theses wastes were also focused such
as reusable, non-reusable wastes or recyclable, non-recyclable including
dumping procedures and quality assessment of dumping yard.
Results and discussion
During
data collection for the purpose of study assessment using the questionnaire ,
it is found from the sample that most of the tanneries are run as Sole Proprietorship (7 tanneries), partnership farms
(4 tanneries) and Limited Company (1 tannery) in ownership where 750 workers
work altogether. All types of tanning methods (chrome, vegetable and
combination) are applied to convert the putrescible raw hides and skins into
leather which depends on the quality of raw hides and skins or according to the
desirable properties of leather that buyers want. 6 tanneries from the sample
carry out beam house to finishing operation producing quality wet blue, crust
and finished leather, 5 tanneries are involved in beam house and wet back
operations to produce wet blue and crust leather but only 1 tannery perform wet
back operation and produce crust leather
as it has newly started its production. The leathers produced by these
tanneries generally exported to foreign and rest that are tanned without any
buyers order are sold in local market especially for making leather accessories
results annual turnover of total 102 million BDT/ sq. ft (8.5 million BDT/ sq.
ft in average).
For
the purpose of leather production from raw hides and skins, the tanneries
producing all types of leathers generate large number of solid wastes. Tanneries
producing both wet blue and crust generate moderated solid waste and only the
tanneries producing crust leather generates less amount of solid wastes. The quantity
of generated solid wastes by the tanneries is enlisted in table II in case of
processing 100 kg hides and skins.
Table
II: Quantity of generated solid wastes in processing 100 kg of raw hides and
skins
Sl. No.
Name of solid
waste
Generated from
Quantity (in
kg)
1
Curing salt
Desalting
3.1
2
Raw hide/skin trimmings
Pre-soaking
8
3
Hairs
Liming
2
4
Fat & tallow
Liming
2.5
5
Limed fleshing
Fleshing
16
6
Limed sludge/trimmings
Fleshing
3.8
7
Bated scuds
Bating
0.5
8
Chrome sludge
Tanning
1
9
Wet-blue trimming
Post tanning
2.3
10
Split
Splitting
5
11
Shaving dusts
Shaving
7.5
12
Crust trimmings
Crust finish
3.4
13
Buffing dusts
Finishing
2.5
14
Finishing trimmings
Finishing
2
A
comparison between the quantities of generated solid wastes obtained from the
face to face interview sessions with the table I is show under a graphical
representation which shows that tanneries generate solid wastes mostly from
beam house operations, moderate amount from wet back and small amount during
finishing.
Figure IV: Comparison between
quantities (in kg) generated solid wastes evolved per 100 kg wet salted
hide/skin treatment.
The
tanneries not only generate a larger amount of solid waste but also discharge
significant amount of tannery effluent mostly from beam house operation and wet
back. The discharged effluents originated from every stage of 100 kg hides and
skins processing are shown in table III
Table III: Effluent originated from every stage of 100 kg
hide and skin processing
Stages
Generated
Effluent
Quantity in
liter
Treatment
technology & utilization
Presoaking
200
CETP
Soaking
150
CETP
Liming
100
CETP
Fleshing
& Unhairing
20
CETP
Washing
60
CETP
De-liming
50
CETP
Bating
50
CETP
Washing
60
CETP
Pre-tanning
200
CETP
Tanning
80
CETP
Samming
5
CETP
Wet
back
200
CETP
Re-tanning
& Dyeing
100
CETP
Fat-liquoring
150
CETP
Top
dyeing & Fixing
100
CETP
Setting
out
2
CETP
Vacuum
drying
5
CETP
Finishing
1
CETP
During
focused group discussion on the dumping process of these generated solid
wastes, it has come out that the generated solid wastes generated from beam
house process are totally disposed in the dumping whether few of them can be
either reusable or recyclable, meanwhile wastes evolved from wet back and
finishing process are reused as well as recycled in form of various
by-products. The reuse and recyclable solid wastes are enlisted in table IV.
Table IV: Treatment technology of
solid wastes originated from hide/skin processing
Wastes
Generated
from
Treatment
technology
Curing Salt
De-salting
Reuse
Raw
hide/skin trimming
Pre-soaking
Gelatin
manufacturing, Toe-cap making
Fat &
tallow
Liming
Poultry feed
Wet-blue
trimming
Post tanning
Animal feed
Splits
Splitting
Glove
leather production
Shaving dust
Shaving
Adhesive
making
Crust
trimming
Crust
finishing
Small
leather accessories
Buffing dust
Finishing
Glue
production
Famished
trimming
finishing
Footwear and
other leather goods making
Conclusions
Wastes
that can neither be reuse nor recycle because of less developed recycling
technologies and lacking of any type of recycling factories around TIED. Since
the TIED is still under construction, the leather technologists highly believed
that government would take necessary steps in case of proper solid waste
management system.
Study Limitation
Though
the study was conducted quite successfully, some limitation was observed. Due
to less access to the tanneries during data collection, the sample size turned
small and resulted less informative. The study may not be able to draw the
overview of solid waste management system but could show a simple sketch.
Acknowledgements
The authors are humbly grateful to Institute of Leather Engineering &
Technology (ILET) for providing all facilities, and responsible for any types
of errors and omissions. They sincerely acknowledge all leather technologists
who participated in interviews for the purpose of data collection and Minhazul
Abedin, Junior research fellow, SAIST for unconditional support and
co-operation.
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