|
Environmental Report on
Sugar Sector |
|
By Environmental Technology
Program for Industry |
| 1.Introduction |
|
This report is a part of the ETPI demonstration project component. The
purpose of this report is to address the environmental problems of sugar
sector. The report has been prepared on the basis of the findings of the
environmental audits of three sugar industries which were conducted by ETPI
in its first phase. The study was jointly carried out by two leading firms of
the ETPI consortium i.e. National Environmental Consulting (Pvt) Ltd. and
Haskoning Consulting Engineers and Architects, The Netherlands. This report
is a step towards the dissemination of information about the environmental
problems of sugar manufacturing units along with the possible solutions and
the investment required to mitigate these problems and to comply the present
and future environmental legislation.
|
| 1.1
Environmental Problems of
Sugar Sector |
| The sugar industry is considered a large water
consumer and polluter. However, the situation varies from country to country
as shown in the Table 1.1. |
| Table 1.1: Effluent Characteristics Of Various Cane
Sugar and Refining Waste Streams In Different Countries |
|
Parameter |
Puerto Rico |
Hawaii |
Philippines |
Louisiana |
India |
Pakistan* |
|
pH |
5.3-8.8 |
- |
5.3-7.9 |
- |
6.8-8.4 |
4.7-6.5 |
|
BOD5(mg/l) |
112-225 |
115-699 |
130-1220 |
81-562 |
267-660 |
600-4853 |
|
COD(mg/l) |
385-978 |
942-2340 |
50-1880 |
720-1430 |
890-2236 |
1037-19234 |
|
SS (mg/l) |
100-700 |
915-3590 |
240-5440 |
150-8120 |
504-936 |
- |
|
TSS (mg/l) |
500-1400 |
3040-4500 |
- |
409 |
792-2043 |
185-526 |
|
Temperature (C) |
31-49 |
- |
34-48 |
- |
- |
- |
|
| Sources: UNIDO,"Towards a cleaner and more
profitable sugar industry", Vol. 2, 1997 *ETPI, "Sugar Sector
Environmental
Audit Reports", 1998 |
The environmental concerns associated with
sugar production include water and air pollution and the disposal of solid
wastes. With proper management, environmental impacts can be negligible. If
Q is the quantity of cane processed, then the immediate need of water in a
sugar processing plant would be approximately 20Q. This could be reduced to
0.9Q if all the possibilities for recycling are employed, and to 1.3Q with
partial recycling.
Pakistani sugar mills rarely exploit the possibilities of reusing wastes
in the process, or as by-products. A considerable development of
sucrochemistry and ethanol applications is expected in the near future. This
development will bring forth problems to a scale (especially associated with
pollution by aggressive molasses and vinasses) that make current problems
appear insignificant.
ETPI conducted environmental audits of three sugar mills. The
environmental audits and the action plan investigations lead to the
identification of following environmental issues:
- Main sources of water pollution are from mill house (floor washing,
turbine cooling water, bearing cooling water, imbibition water), process
house (washing of evaporator, heater, and pan), boiler house (wet
scrubber), and cooling pond (waste water).
- Main sources of solid waste are from mill house (bagasse), process
house (filter cake and molasses), and boiler house (fly ash).
- Most of flue gases are emitted from the boiler house.
- Sugar effluent is normally high in BOD5,
COD and TSS. BOD5 of
Sugar mills effluent is normally in the range of 1000 to 4500. These
values are much higher than the NEQS. It is important to note that out of
three mills one of the mill with higher crushing capacity is producing
less pollution. This establishes the fact that better in house management
for pollution control can lead to much better results.
- Air emissions of most of the sugar mill are with in limits of
NEQS.
- Noise levels are high in almost are the sections of the sugar mills.
Emphasis on the environmental issues is new both at the unit and
institutional level. Some progressive mills have already taken major
decisions for the implementation of environmental solutions. Many are
reviewing the situation and will take the right decisions in the near
future.
In the last two environmental workshops organized by
PSST, it was decided
that owing to sugar sector peculiar conditions sector environmental policy
should be prepared. |
| 2.
The Sugar Industry |
| 2.1
Profile |
| Sugar industry is playing an important role in
the economy of Pakistan. The progress in technology has been made by
industry itself. At the time of the independence there were only two sugar
mills one at Rahwali, Punjab and the other at Takhat Bai, NWFP. Total
quantity of sugar produced during 1947-48 was 7,932 tonnes. Today there are
75 sugar mills all over the country. Majority of these sugar mills are
based on sugar cane. The total crushing capacity of this industry is
approximately 3.0 million tonnes cane per day.However, only four mills
process beet for sugar production. Geographical distribution of these mills
is given in Table 2.1. |
| Table 2.1:
Number of Sugar Mills in Different Areas of Pakistan |
|
S.No. |
Area |
No. of
Mills |
Percentage |
|
1. |
Punjab |
38 |
50.66 |
|
2. |
Sindh |
30 |
40.00 |
|
3. |
NWFP |
6 |
08.00 |
|
4. |
Balochistan |
Nil |
0.00 |
|
5. |
Azad Kashmir |
1 |
1.33 |
| |
Total |
75 |
99.99 |
|
| Source: Final report 1996-97, Pakistan Society
of Sugar Technologist. |
Molasses is a by product of sugar manufacturing
process and is exported to other countries. In Pakistan some sugar mills
(seven) convert a part of their molasses into industrial alcohol..
Distribution of Sugar mills |
|
Table
2.2: No. of Distilleries Operating in Sugar Mills in Pakistan |
|
S.No. |
Province |
Number |
|
1 |
Sindh |
02 |
|
2 |
Punjab |
04 |
|
3 |
NWFP |
03 |
| Total |
|
09 |
|
|
| Source: PSST |
| also operating distillery is given in Table 2.2
This development in the sugar sector under any
criteria is a great achievement. There are many reasons behind this success.
Major contributors to this achievement are the government's continuous
incentives, establishment of local technology vendors (HMC etc.),
commitment and hard work of mill owners and employess, and progressive roles
of Pakistan Society of Sugar Technologists (PSST) and Pakistan Sugar
Mills Association (PSMA).
Sugar sector can be classified as one of
the most organized sector with respect to its institutional arrangements.
Establishment of PSST is the most progressive idea of early fifties.
PSST is
performing most of the desired functions attached
to its basic idea. In this era of technology development and change, PSST
provides forums to sugar technologists and mill owners to discuss
and share indigenous and international technological developments in the
sugar sector. |
| 2.2
Sugar Manufacturing |
| Isolation and purification of sucrose from
sugarcane is the ultimate goal of sugar processing. Process chemistry is
designed for maximum removal of non-sugars with minimum destruction of
sucrose. Cane preparation initiates the process and finally refined cane
sugar or white sugar is produced, in two stages.
In the first stage, the
extraction of juice from sugar cane and conversion to raw sugar is achieved.
Nearly, all sugar mills employ similar process for this purpose. In the
second stage raw sugar is refined to produce white sugar. However, processed
vary from mill to mill. Table 2.3 gives an overview of various processes and
their year of adoption by Pakistani industry. |
| Table 2.3: An
Overview of Various Processes Employed By Pakistan's Sugar Mills |
|
S. No. |
Processes |
No. of Mills
1976 |
No. of Mills 1992-93 |
No. of Mills 1996-97 |
Year of Introduction |
|
1 |
Double Carbonation double sulphitation (DCDS) |
20 |
10 |
04 |
1936-37 |
|
2 |
Double Sulphitation (DS) |
01 |
01 |
- |
1938-39 |
|
3 |
Defecation-Remelt-Recrystallization (DRR) |
01 |
01 |
- |
1971 - 72 |
|
4 |
Defecation-Remelt-
Phosphitation(DRP) |
01 |
13 |
24 |
1972-73 |
|
5 |
Defecation-Remelt-
Carbonation(DRC) |
02 |
25 |
21 |
1971-72 |
|
6 |
Defecation -Remelt -Sulphitation
(DRS) |
02 |
05 |
1 |
1972-73 |
|
7 |
Defecaion-Remelt-Carbonaion
& Sulphitation (DRCS) |
--- |
08 |
11 |
1977-78 |
|
8 |
Defecation-Remelt
phosphitation and sulphitation (DRPS) |
---- |
--- |
5 |
NA |
|
9 |
DRT |
-- |
-- |
2 |
1985-86 |
|
Total Mills |
|
27 |
63 |
68 |
|
|
| Source: * Improved Carbo-floatation Process for
melt Treatment, Proceedings, 28th convention,PSST. |
| ** Extracted from " Synopsis of Technical
Results Season 1996-97" |
|
| All these
processes have their own advantages and disadvantages. Major disadvantage of
DCDS process is the generation of high quantity of filter press mud, upto 8
% of cane crushed whereas other processes generate about 3 %. It is reported
that mills operating with DCDS process are also working at their BMR
program
to switch over to DRC or DRP processes. |
| 3.
Waste Generation |
| All three
categories of waste, i.e. liquid, air and solid, are generated from sugar
industry. Noise problem is also a significant problem. |
| 3.1
Sources of Waste Generation |
| Table 3.1 gives
an overview of the main sources of waste generation with respect to sugar
manufacturing processes. Mill House
The liquid effluent from mill house
consists of floor washings, and oily water ex-lubricating systems, and is
considered mildly contaminated in terms of pollutant loading. Bagasse is a
by -product of mill house which on an average contains 50-52 % of moisture
and sent to boiler house where it is burnt as fuel. It is sold for
downstream use for the production of chipboard.
Process House
The liquid effluents from process house
consists of evaporator, and floor washings. This wastewater contains sugar
contents and washing chemicals, and are considered more contaminated than
mill house effluent. Mud cake or filter cake is produced as a result of
vacuum filtration.
Boiler House
The boiler house generates the following
types of wastes:
- Hot flue gases, containing particulate
matter, carbon monoxide, oxides of nitrogen and sulfur.
- Ash from combustion chamber.
- Fly ash originating from boiler stacks,
and
- Liquid effluents from wet serubbing
unit.
Distillery Unit
The most aggresive liquid effluent
originates from the distillery unit and are termed as stillage, in which
BOD5 and COD concentrations are in the range of 40,000 mg/l and 100,000
mg/l, respectively. The lutter water from the rectifying column is a
relatively mild effluent. |
| 3.2
Type and Characteristics of Wastes |
| All the three
types of wastes gaseous, solid and liquid, are generated from sugar mills.
This section describes the nature and extent of these wastes. |
| Table 3.1:
Sources of By-Products and Waste Generation |
|
Main Input |
Process Step |
Wastes/By-Product |
|
Sugar cane |
Mill House |
|
|
Sugar Juice |
Process House |
-
Filter Cake (Solid
waste)
-
Washing of different
components such as, Evaporator, Juice heater, Vacuum pan, classifiers,
etc, generate aggresive effluents having high BOD5,
COD and TDS
concentrations.
Molasses |
|
Bagasse, Furnace oil |
Boiler House |
|
|
Water + Chemicals |
Cooling Pond |
|
|
Molasses |
Distillery |
|
|
| Table 3.2:
Characteristics of Press Mud |
|
S.No. |
Parameters |
Values |
|
1. |
Moisture % |
74.00 |
|
2. |
Minerals % |
28.92* |
|
3. |
Ca Co3
% |
0.48* |
|
4. |
Organic Matter % |
71.10* |
|
5. |
Nitrogen % |
1.68* |
|
6. |
Phosphorous % |
1.03* |
|
7. |
Potassium % |
0.67* |
|
8. |
Sulfur % |
5.42* |
|
9. |
Sodium % |
0.33* |
|
10. |
Calcium % |
2.50* |
|
11. |
Magnesium % |
1.03* |
|
12. |
Zinec ppm |
143.00* |
|
13. |
Copper ppm |
60.00* |
|
14. |
Manganese ppm |
276.00* |
|
15. |
Iron ppm |
556.00* |
|
| Source : ETPI
Audit Reports *Dry basis |
| Table 3.3: Air
Emissions Measurements |
|
Parameter |
|
Boiler Combustion Mode |
|
|
(mg/Nm3) |
NEQS |
Fuel Oil |
Bagasse |
Mixed Fuel |
|
|
Mills |
|
1 |
2 |
3 |
1 |
2 |
3 |
1 |
2 |
3 |
|
Hydrogen Sulphide |
10 |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
|
Carbon Monoxide |
800 |
Nil |
851 |
2.3 |
404 |
543 |
81 |
346 |
324 |
17 |
|
Sulfur Dioxide |
400 |
132 |
297 |
53 |
Nil |
16 |
Nil |
Nil |
59 |
Nil |
|
Oxides of Nitrogen |
400 |
23 |
154 |
46 |
38 |
201 |
30 |
30 |
251 |
34 |
|
Particulate Matter(Fuel Oils) |
300 |
73 |
47 |
23 |
1686* |
17 |
213 |
219 |
83 |
102 |
|
Smoke (No) |
2 |
3 |
2 |
2 |
1 |
1 |
1 |
2 |
1 |
1 |
|
Lead |
0.5 |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
Nil |
|
Zinc |
5.0 |
0.08 |
- |
0.02 |
0.55 |
- |
0.14 |
0.42 |
- |
0.1 |
|
Cadmium |
0.1 |
Nil |
- |
Nil |
Nil |
- |
Nil |
Nil |
- |
Nil |
|
Copper |
1.0 |
Nil |
- |
Nil |
0.082 |
- |
Nil |
0.04 |
- |
Nil |
|
Arsenic |
1.0 |
Nil |
- |
Nil |
Nil |
- |
Nil |
Nil |
- |
Nil |
|
Mercury |
0.01 |
Nil |
- |
Nil |
Nil |
- |
Nil |
Nil |
- |
Nil |
|
| Soure : ETPI
Survey. |
| *: This high value
seems a laboratory testing error. However, there is a possibility that under
abnormal conditions, values can go as high as stated. |
| Table 3.4:
Average Characteristics of Combined Wastewater of Sugar Mill |
|
Description |
Cane Crushing |
Flow |
pH |
COD |
COD |
BOD5 |
BOD5 |
TSS |
TSS |
|
Combined |
tonnes/day |
m3/day |
|
mg/l |
kg/day |
mg/l |
kg/day |
mg/l |
kg/day |
|
Wastewater |
|
|
|
|
|
|
|
|
|
|
Mill-1 |
2800 |
3882 |
6.00 |
12107 |
46999 |
2798 |
10862 |
526 |
2042 |
|
Mill-2 |
3000 |
6187 |
4.67 |
19234 |
119001 |
4853 |
30026 |
185 |
1145 |
|
Mill-3 |
6647 |
3040 |
6.5 |
1037 |
3152 |
600 |
1824 |
274 |
833 |
|
Mill-3+ Distillery* |
6647 |
3240 |
- |
7716 |
25000 |
4319 |
13994 |
12000 |
38880 |
|
Distillery |
6674 |
200 |
4.7 |
108667 |
21733 |
60830 |
12166 |
12160 |
2432 |
| |
NEQS |
|
6-10 |
150 |
- |
80 |
- |
150 |
- |
|
| Combined
Wastewater: (Mill-House + Process House + Cooling Pond Over flow) *Estimated
Values |
| Table 3.5:
Noise level at Different Mill Areas |
|
# |
Location |
Noise Level (dB) |
|
Sugar Mill |
|
|
|
1 |
Centrifugal machine |
86-87 |
|
2 |
Raw station for the sugar |
83.5-85 |
|
3 |
Vacuum release |
102-104 |
|
4 |
Sugar dry units |
91-92 |
|
5 |
Compressor for air supply |
90-92 |
|
6 |
Milling |
88-91 |
|
7 |
Mill turbines |
92-94 |
|
8 |
Juice clarification station |
88-89 |
|
9 |
Juice evaporation station |
82-93 |
|
10 |
Power house turbine |
93-105 |
|
11 |
Boilers |
83-109 |
|
12 |
FD fan |
94-96 |
|
13 |
Delivery pumps for sugar and molassess
supply |
89-90.5 |
|
Distillery Unit |
|
|
|
1 |
Air blower station |
99-102 |
|
2 |
Yeast separation station |
96-98 |
|
3 |
Control room |
92-94 |
| |
NEQS |
80 |
|
| 4.
Acknowledgement: |
| The above
information constitutes extracts from special issue of Monthly Environmental
News on Sugar industry published by FPCCI in July 2001. Full text can be
obtained directry from FPCCI. |
| |
