Study area
In the present study, two major districts of Tamil Nadu were considered viz a viz. Trichy and Thanjavur. Tiruchirappalli Municipal Corporation, Trichy, Tamil Nadu, India is one of the important tourists and holy place in South Tamil Nadu. Tiruchirappalli Municipal Corporation is divided into four zones viz., Srirangam, Ariyamangalam, Abishekapuram and Ponmalai; they were divided into 65 wards for administrative purposes. Ariyamangalam dump site covers a spread up area of nearly 47.70 Ha and was located at a distance of 12 km from the city center and in Trichy-Thanjavur Road with the inception during 1967. The dumping site is positioned at 10.48’N and 78.43’ E (Fig. 1). The dumping yard is elevated to a height of + 75.88 m above the mean sea level. The trench method of waste burial is adopted in the Trichy landfill site. The dumped waste is covered with a layer of soil at regular intervals to a depth of 15 to 30 cm; the soil type in the landfill site is a sandy clay.
The Thanjavur municipal corporation is having a dumping site with a total spread up area of 20.23 acres for the solid waste management activities and it’s located at 10°47’ N and 79°7’ E (Fig. 2). The city generates a 124MT of garbage every day out of which 116MT waste was being collected by Municipal Corporation. In this city, there are 14 zones within which 51 wards are located. The average temperature of this City is 28.7°C and the normal annual rainfall is 1053mm.
Collection Of Data
The information’s related to the two selected dumpsites (Trichy and Thanjavur) like amount of waste generated, fraction of waste disposed, population growth over years and disposal strategies adopted were obtained from the Municipal Corporation office. Additionally, the data required by the LandGEM software like methane production capacity, constant methane value and % of content by volume were entered the default values as prescribed by the United States Environment Protection Agencies (USEPA), and finally methane emission value is calculated. As per the Censes, 2011 the population of Tiruchirappalli Municipal Corporation is just more than 8.47 lakhs as per 2011 censes whereas in Thanjavur the population was 24.1 lakhs as per Census 2011, the population growth rate in both the cities were increasing rapidly. The compressive waste management plan that includes the methane emissions and potential for energy source for the Trichy and Thanjavur was computed for a ground period of 60 years, the waste composition was tabulated in Table 1. Appropriately to estimate the amount of methane emissions by LandGEM software, the most vital component is the weight of waste produced during plan period and LandGEM determines the methane mass produced by using the mass of waste deposited and the methane generation capacity.
Table 1
Physical composition of Municipal Solid Wastes in Trichy and Thanjavur
Parameters | Trichy Waste Composition in % | Thanjavur Waste Composition in % |
Biodegradable (Food wastes, garden wastes, etc.) | 75.0 | 55.55 |
Glass | 1.5 | 0.01 |
Rags | 5.0 | 0.41 |
Paper | 1.0 | 5.59 |
Plastic | 1.0 | 5.79 |
Leather and Rubber | 0.5 | 0.07 |
Metals and other domestic hazardous | 1.0 | 0.06 |
Inert | 15.0 | 32.52 |
Total | 100.0 | 100.00 |
Present Condition Of The Dumping Yard
Solid Waste Management in Tiruchirappalli and Thanjavur Cities are entirely collected and managed by the corporation. The corporation has allowed the dumping of Trichy solid waste at the Ariyamangalam composite yard since 1967, and Thanjavur solid waste at Srinivasapuram since 2002 without foreseeing the problems that the accumulated solid waste can pose to a growing city. The generated waste is directly buried into the dumping yard without a proper compaction and segregation. With an estimated 12 lakh tons of garbage accumulated down the years and more than 400 tons added to it every day, the garbage dump literally presents a massive problem to the local residents and civic body as well. Additionally, the dumped wastes are not properly covered, and bottom is not lined, leading to spread of contamination. The generated leachate contaminates the ground water, and the absence of cover generates noxious gases. The dumpsites are freely accessible by the scavengers and rag pickers for collecting the recoverable/ recyclables and some valuables in an unhealthy and unhygienic manner. Subsequently, there are many food starving animals like cattle’s, pigs, buffaloes, and dogs scavenging for food waste in the dumpsite (Fig. 3(a)-(c)). Due to the above circumstances, the spread of diseases like cholera, hepatitis, dysentery, and other water borne diseases were reported in the surrounding regions.
Description Of The Landgem Model
A landfill gas emissions model (LandGEM) model was developed by the US environmental protection agency. It is an automated estimation tool with a Microsoft Excel interface that can be helps to determine emission rate of methane, carbon dioxide and total landfill gas from the municipal landfill site through the first order equation. Some real field data need to provide such as landfill open year, landfill closure year, design capacity of the landfill and amount of being dumped every year to the corresponding landfills. The decay rate (k) and the methane potential capacities of the landfill waste (Lo) are the two vital factors that govern the amount of methane emissions. Additionally, the prediction of landfill gas emissions also depends on waste biodegradability factor, microbial usage rates, volatile solids concentrations, availability of micro and macro nutrients, pH of the waste, moisture and temperature of waste, and waste composition of the specific location.
\({Q}_{{CH}_{4}}= \sum _{i=1}^{n}\sum _{j=0.1}^{1}k{L}_{o}\left(\frac{{M}_{i}}{10}\right){e}^{-k{t}_{ij}}\) -------------------------------------------(1)
QCH4 = annual methane generation in the year of the calculation (m3/year)
i = 1-year time increment
j = 0.1year time increment
n = (year of the calculation) - (initial year of waste acceptance)
k = methane generation rate and taken as 0.050 (year-1)
Lo = potential methane generation capacity and taken as 170 (m3/Mg)
Mi = the mass of waste accepted in the year (Mg)
tij = the age of the jth sector of waste mass Mi accepted in the ith year
To determine the site-specific value of (Lo) the following equation is applied (Osra et al, 2021)
\({L}_{0}=MCF x DOC x DOCF x \frac{16}{12} x F\) -------------------------------------------------(2)
MCF = methane correction factor (1 = well managed landfill, assumed in this case XXX),
DOC = degradable organic carbon (fraction),
DOCF = fraction DOC dissimilated, and
F = fraction of methane in landfill gas (measurement at landfill has indicated a value of 56% CH4 in biogas). The site-specific degradable organic carbon (DOC) is calculated based on IPCC (1996) formula,
\(\% DOC\left(Dry weight\right)=0.4C + 0.17B+0.15 C+0.3 D\) -------------------------(3)
A = % paper and textiles,
B = % garden waste, park waste, or other non-food organic putrescible
C = % food waste, and
D = % wood or straw DOCF can be determined through the lignin content of the volatile solid (VS) (author name, year):
\(DOCF=0.83-0.028 LC\) ------------------------------------------------------------------(4)
0.83 = empirical constant; 0.028 = empirical constant; and LC = lignin content of the VS expressed as a percent of dry weight from leachate sample. From the above expressions the value of methane generation potential (L0) is estimated for Trichy and Thanjavur are 71.23 and 56.37 m3/ Mg respectively.
Estimation Of Energy Potential
The landfill gas especially methane has higher energy potential and can be recovered as an alternative energy source. The energy generation potential (Ep in kWh per year) from the methane emissions from the Trichy and Thanjavur landfills is estimated by the following equation (Ayodele et al., 2017; Rodrigue et al., 2018),
\({\text{E}}_{\text{p}}= \frac{{0.9 \times {\text{Q}}_{\text{m}\text{e}\text{t}\text{h}\text{a}\text{n}\text{e}} \times \text{L}\text{H}\text{V}}_{\text{m}\text{e}\text{t}\text{h}\text{a}\text{n}\text{e}} \times {\eta } \times {\lambda }}{3.6}\) --------------------------------------------------(5)
The Qmethane is the amount of methane gas emitted in cu. m from the landfills during the particular year, LHVmethane is the Lower Heating Value of methane and usually taken as 37.2 MJ per cu. m (Cyril et al., 2018), η is the electrical conversion efficiency for the internal combustion engine and usually taken as 33%, λ is the collection efficiency of methane from landfills and usually taken as 75%, 0.9 is the empirical coefficient and 3.6 is the conversion factor from MJ to kWh.