Solid waste management has become a global problem. Littering of wastes on streets not only causes inconvenience and aesthetic problems, but also has a lot of impact on human health Municipal Solid Waste Management (MSWM) is highly neglected aspect of Delhi. At present approximately 6000 tons of waste is generated per day which is disposed in the three existing landfills. The three landfills are almost saturated therefore some alternate method of disposal should be designed. The present paper discusses the energy content of MSW of Delhi so that some suitable technology can be adopted for the disposal of wastes. Generally evaluation of the heating value of Municipal Solid Waste (MSW) is done experimentally by using bomb calorimeter and theoretically by using Dulong’s equation. In this paper, regression analysis is used to develop a predictive model of the energy content for MSW of Delhi.
2. Mahapatra 056
Table 1. Details of zonewise survey (Figures in %)
Physical
Composition
Mongolpuri
AtaThakurdas
Greenpark
Subhasnagar
Trilokpuri
NaveenSahadra
Shakurpur
Chandnimahal
Outremline
Kutubroad
Aryasamaj
Sundarnagri
Foodwastes 9.7 5.6 40.7 5.5 10.6 9.6 3.7 42.1 57.7 5.6 6 8
Paper 2.7 8.6 5.9 8.7 9.7 2.7 4.1 3.8 7.7 8.6 10.5 6.1
Plastic 1.9 11.1 4.7 6.2 5.8 2 3.3 1.3 5.8 11.2 9.9 48
Textile 12.4 11.4 4 6.5 5.6 12.6 0.7 10.1 7.7 13 13.3 3.7
Glass 2.3 8.6 4.8 6.1 8.1 2.3 3.3 4.4 5.8 9.1 16.9 5
Metals 0.9 6.7 1.7 4.4 3.2 0.9 3.4 1.2 3.8 6.8 14.8 1.2
Dirt Ash
etc. 70.1 23 34.2 56.9 39.4 69.9 72 19.1 11.5 22.9 16.5 24.9
# Source: white paper on pollution in Delhi with an action plan government of India ministry of environment &
forests chapter 5 (1997)
appears to be one of the options for management of
municipal solid waste of any area (Qudais and Qdais
2000)
Energy Content of MSW of Delhi
The determination of heating value of MSW is done
either experimentally using a bomb calorimeter or
theoretically using mathematical models. The models
are based on the physical composition, proximate or
elemental analysis. The disadvantage of using
Dulong”s equation (elemental analysis) is that the
sample size used for this equation is very small (1-10
mg) and skilled workers are required to carry out the
analysis (Jimenez andGonalez. 1991, Dermirbas 1996,
5 (76) and9/10 , Raveendran and Ganesh 1996
Fernadez, Diaz and Xiberta 1997). On the other hand,
the models which are based on proximate analysis or
physical composition (Liu ,Paode and Holsen 1996 and
Reddy, Basha, Joshi, Sravan, Jha and Ghosh 2005) fit
well within the locality but do not give good results for
other places. Thus considering the above factors, this
paper aims to develop a new model for the calculation
of HCV (high calorific value) for Delhi. The equations
proposed in this model are based on data either from
the physical, proximate or elemental analysis of MSW
of Delhi (as collected from various sources). The
physical composition analysis is based on the heat
generated from various sources like paper, plastic,
garbage etc. The elemental analysis is based on the
percentage of carbon, oxygen, nitrogen and sulfur in
the waste while the proximate analysis includes an
assessment of moisture, volatile combustible matter
fixed carbon and ash. Since the MSW of any area is
highly heterogeneous in nature the HCV calculated by
proximate or elemental analysis is not very accurate.
Thus an attempt is made to find the heating value using
physical composition. The following equations are
used for the development of the model.
H = 88.2 R + 40.5 (G+P) – 6 W ,where {1}
H = net calorific value (Kcal/kg)
R = plastic, percent weight on dry basis
G = garbage, percent weight on dry basis
P= paper, percent weight on dry basis
W = water, percent on dry basis
Equation used for ultimate analysis is Dulong Model {2}
H = 81 C + 342.5 (H-O/8) + 22.5 S –6 (9H+W), where
H = net calorific value (Kcal/kg)
C = Carbon (% wt)
H = Hydrogen (% wt)
O = Oxygen (%wt)
S = Sulphur (% wt)
Equation used for proximate analysis Traditional Model
H= 45 B – 6 W where {3}
H = net calorific value (Kcal/kg)
B = combustible volatile matter
W = water (% dry basis)
MATERİAL AND METHOD
A systematic approach in managing solid waste is
necessary because there is a variation in the
composition of MSW from area to area. A detailed
physical composition of MSW has been carried out
zone wise in Delhi by NEERI in 2000 The analysis
covered all areas such as high income group (HIG),
middle income group (MIG), vegetable market,
industrial areas, construction sites etc. The components
of waste identified in the analysis are food waste,
paper, plastic, textile, glass and metal (as shown in
Table 1).
For sample calculation, Modified Dulong’s Equation is
used, which is :
E= 81C + 342.5 (H-O/8) + 22.5 S – 6(9H-W) {4}
Where, E is the energy content (HHV) of waste in
Kcal/Kg and C, H, O, S & W are percentage weight of
Carbon, Hydrogen, Oxygen, Sulfur and water
3. Study of municipal solid waste of Delhi for energy content
J Environ. Waste Manag. 057
Table 2. Data from the Ultimate Analysis of the components in residential MSW
Component
Percent by weight (dry basis)
Carbon Hydrogen Oxygen Nitrogen Sulfur Ash
Organic
Food waste 48.0 6.4 37.6 2.6 0.4 5.0
Paper 43.5 6.0 44.0 0.3 0.2 6.0
Cardboard 44.0 5.9 44.6 0.3 0.2 5.0
Plastics 60.0 7.2 22.8 - - 10.0
Textiles 55.0 6.6 31.2 4.6 0.15 2.5
*Organic content is from coatings, labels and other attached materials.
Table 3. The HCV values of various localities of Delhi
Localities of Delhi HCV (kcal/kg)
Shakurpuri 0523.924
Mangolpuri 1229.65
Subhashnagar 1217.84
Naveen Sahadra 1241.55
Trilokpuri 1393.26
Ata Thakurdas 1757.39
Kutub road 1843.91
Arya samaj 1862.18
Chandnimahal 2454.54
Outermline 3378.45
Sunder nagar 3384.2
respectively. The elemental analysis of the components
in residential MSW as calculated by NEERI is given
below in Table-2 (Agarwal, Rathore and Gupta 2004)
The mass of C, H, O, N, S and Ash for food waste,
paper, plastic, rags, glass and metals is calculated on
dry basis.
RESULTS AND DİSCUSSİON
Development of the Model
For deriving the mathematical equation linear
regression analysis using SPSS 13 statistical software
is used. The model is based on physical composition of
MSW. The resulting regression equation can be
expressed as :
Y = B0 + B1X1 + B2X2 + ………+ BkXk
Where Y is dependent variable, X1, X2, …..Xk are
independent variables; B0 is intercept of straight line,
B1, B2,…..Bk are unstandarized regression
Coefficients The energy content is the dependent
variable and the physical composition of the waste
(Food waste,paper, plastic textile) is the independent
variable The equation which is developed from the
above model, using the various physical compositions
(in percentage weight) (Mohapatra and Gadgil 2008)
EC = 0.001 + 41.337 (FW) + 33.753 (P) + 59.611 (PL)
+ 50.346 (T) {5}
Where, EC = Energy content of the waste in Kcal/Kg
FW = Food waste
P = Paper
PL = Plastic
T =Textile
The average HCV of Delhi from the above table.3 is
1887.16 Kcal/kg and the actual average value of HCV
of Delhi is less than 3000 kcal/kg (from equation 4).
The difference in the theoretical and observed value is
due to the fact that the data used in the model is largely
for the low and middle income group localities.
CONCLUSİON
As seen from the calculation of Energy Content of
MSW the calorific values is less than 3000Kcal/kg
whereas in the developed countries it is 9200 Kcal/kg
Hence incineration of waste alone cannot be a solution
to the problem of disposal even in the capital state of
India i.e. Delhi. Better segregation facilities at the site of
collection of waste should be provided to give a higher
value of HCV of MSW.Gasification technologies enable
conversion of MSW into value added products, such as
liquid fuels and commodity chemicals as well as
electricity, and do so at greater efficiencies than
conventional incineration (Stevens D. 1994 ) Therefore
other technological options should be also considered
for better waste management.
REFERENCES
Agarwal GD, Rathore APS, Gupta AB (2004). A simple