In order to solve the problem of the management of municipal solid waste in Abidjan (Cote d’Ivoire), a sanitary landfill has been designed in Kossihouen. Despite the adverse greenhouse effects of the methane, this gas has a potential of electrical energy. The estimation of methane emissions from the waste can be an economic and useful way for more accurate control and management of waste disposal in Kossihouen. Therefore, conducting this study is essential. Methane emissions were estimated based on the methane generation constant K and the methane generation potential L0 using LandGEM 3.02. The results show that the quantity of methane emissions was 7.97E+07 m 3/year. Based on this result, the methane content can generate 10% of total electricity consumed in Abidjan in 2026. This paper could serve as a source of scientific information for decision making on environmental sustainability in waste-to-energy projects in Cote d’Ivoire.
Increasing growth of population and urbanization and subsequent development of industrial units have led to greater production of wastes and pollutants. The main environmental contaminants are Municipal Solid Wastes (MSW), million tons of which are daily produced worldwide [
Landfills that are managed to minimize environmental impact and promote waste degradation can be integrated with technologies that include energy recovery systems. Many of the technologies that have been used to promote more sustainable landfills focus on the methods to foster waste treatment [
In the economic capital city of Cote d’Ivoire (Abidjan), the quantities of waste generated increased by about (3.75%) between 2008 and 2014. This city is the largest MSW producer in the country. It produces about 3800 tons of solid waste a day. In Abidjan, MSW disposal has been a chronic problem [
Kossihouen is the first sanitary landfill in the autonomous district of Abidjan. It is located at the intersection of the North Highway and the unpaved road linking this village to Songon between latitudes 5˚40 and 5˚30N and longitudes 4˚20 and 4˚10W (
The Ivorian climate is tropical. The average annual temperature is 26.6˚C. Abidjan has an annual average rainfall of 1784 mm [
LandGEM is an automated tool for estimating emission rates for total landfill gas, methane, carbon dioxide. LandGEM can use either site-specific data to estimate emissions or default parameters if no site-specific data are available [
The LandGEM (version 3.02) emission methodology can be described mathematically using the following equation [
Q C H 4 = ∑ i = 1 n ∑ j = 0 , 1 1 K L 0 ( M i 10 ) e − K t i j
where: Q C H 4 = annual methane generation in the year of the calculation (m3/year),
i = 1 year time increment,
n = (year of the calculation) − (initial year of waste acceptance),
j = 0.1 year time increment,
K = methane generation rate (/year),
L0 = potential methane generation capacity (m3/ton),
Mi = mass of waste accepted in the ith year (ton),
tij = age of the jth section of waste mass Mi accepted in the ith year (decimal years, e.g., 3.2 years).
According to the equation, the required inputs for the amount estimation of generated methane are the design capacity of the landfill site, the annual acceptance rate, the methane generation constant K, the methane generation potential L0 and the years of waste acceptance.
In Abidjan, only 65% of generated wastes are collected and transported to the landfill site [
M F ( t ) = 0.65 × M T (1)
M T (tons/yr) is the total mass of waste generated per year
M T ( t ) = P ( t ) × W C × 365 (2)
P ( t ) = P 0 ( 1 + r ) t (3)
P ( t ) is the expected population according to the population growth rate (r) of 4.1%, W C is the waste generation rate, which is of 0.77 kg/capita/day [
The electrical energy (kWh/year) that could be obtained from the methane content of collected landfill gas is estimated as [
E P ( LFTGE ) = L H V methane × 0.9 × Q C H 4 × λ × η 3.6 (4)
where LHV methane is the Lower Heating Value of methane and is given as 37.2 MJ/m3 [
These results showed that the quantity of MSW increases with the growth of the population. The values of methane generation constant (K) and the methane generation potential (L0) have substantial effect on calculation of methane emission [
Methane emission was estimated based on the methane generation constant K and the methane generation potential L0.
Years | Population | Solid weight (ton/year) |
---|---|---|
2018 | 5,527,734 | 1,553,570 |
2019 | 5,754,371 | 1,617,266 |
2020 | 5,990,300 | 1,683,574 |
2021 | 6,235,902 | 1,752,600 |
2022 | 6,491,574 | 1,824,457 |
2023 | 6,757,729 | 1,899,260 |
2024 | 7,034,796 | 1,977,129 |
2025 | 7,323,222 | 2,058,192 |
Composition of MSW | Percentage (%) |
---|---|
Putrescible | 45.42 |
paper-cardboard | 14 |
Leaf | 2 |
Wood | 4 |
Bone and straw | 3.42 |
Textiles | 2.75 |
Glass | 2.5 |
Metals | 1.75 |
Plastics | 8.5 |
Stone | 1 |
Battery | 1.41 |
Sand, dust | 13.25 |
Input Review | |||
---|---|---|---|
Landfill Characteristics | Model Parameters | ||
Landfill open-closure year | 2018-2025 | Methane generation rate | 0.05 Year−1 |
Gas pollutant selected | (MW) | Potential methane generation capacity | 170 m3/t |
Methane | 16.04 | NMOC concentration | ppmv |
Carbon dioxide | 44.01 | Methane content | 50% by volume |
MW: Molecular weight for selected gases, Model parameters base on Clean Air (CAA) Regulations.
Input Review | |||
---|---|---|---|
Landfill Characteristics | Model Parameters | ||
Landfill open-closure year | 2018-2025 | Methane generation rate | 0.149 Year−1 |
Gas pollutant selected | (MW) | Potential methane generation capacity | 108 m3/t |
Methane | 16.04 | NMOC concentration | ppmv |
Carbon dioxide | 44.01 | Methane content | 50% by volume |
Year | Waste Accepted | Waste-in-Place | ||
---|---|---|---|---|
(tons/year) | (short tons/year) | (tons) | (short tons) | |
2018 | 1,009,820 | 1,110,802 | 0 | 0 |
2019 | 1,051,223 | 1,156,345 | 1,009,820 | 1,110,802 |
2020 | 1,094,323 | 1,203,755 | 2,061,043 | 2,267,147 |
---|---|---|---|---|
2021 | 1,139,190 | 1,253,109 | 3,155,366 | 3,470,903 |
2022 | 1,185,897 | 1,304,487 | 4,294,556 | 4,724,012 |
2023 | 1,234,519 | 1,357,971 | 5,480,453 | 6,028,499 |
2024 | 1,285,134 | 1,413,647 | 6,714,972 | 7,386,469 |
2025 | 1,337,825 | 1,471,607 | 8,000,106 | 8,800,117 |
The estimated quantities of methane would be the highest at least three years after the closure of landfill (2025-2028). The mean values were 7.97E+07 and 6.18E+07 (m3/year) for default and determined values of K and L0, respectively. However, the estimated quantities of methane for determined values of K and L0 are greater than those obtained using default values. The estimated quantities of methane gradually decrease until they reach zero. This trend is faster for determined values of K and L0. This could be explained by the fact that the effect of the half-life duration of organic materials such as food waste, paper, wood and textiles to the overall methane emission is related to the reaction rate (k) of the model through the equation k = t 1 / 2 − 1 ln 2 [
In this section, the energy potential assessment of waste to energy from the treatment of MSW in from 2018-2035 is discussed. This assessment is based on the determined values of K and L0. The energy potential of Landfill Gas to Energy (LFGTE) technology depends largely on the methane content of the landfill gas generated, which in turn depends on the methane generation potential of the waste landfilled [
The methane emission has been estimated by using LandGEM model for Kossihouen sanitary landfill, Côte d’Ivoire. This landfill starts operation in 2018 with the purpose to receive the generated solid waste in Abidjan until the year
2025. The maximum methane generation rate occurred during the years 2025-2028. The peck of generation was 7.97E+07 and 6.18E+07 (m3/year) for default and determined values of K and L0, respectively. The intention of this paper is to demonstrate that, based on theoretical information presented above it can be assumed that the quantity of methane produced could be used to cover part of the electrical needs in Abidjan.
Adjoumani Rodrigue, K., Essi, K., Marc Cyril, K. and Albert, T. (2018) Estimation of Methane Emission from Kossihouen Sanitary Landfill and Its Electricity Generation Potential (Côte d’Ivoire). Journal of Power and Energy Engineering, 6, 22-31. https://doi.org/10.4236/jpee.2018.67002