By: Sadah A. T. Muawad , Department of Mechanical Engineering, College of Engineering, Sudan University of Science and Technology, Khartoum, Sudan

Abbreviations

• MSW: Municipal Solid waste management
• CH₄: Methane
• CO₂: Carbon dioxide
• m³/year: Cubic meter per year
• LFG: Landfill gas
• GDP: Gross domestic product
• k: Methane generation rate
• L_o: Methane generation potential
• m³/Mg: Cubic meter per mega gram 
• CAA: The Clean Air Act
• IPCC: The Intergovernmental Panel on Climate Change

Introduction

Municipal Solid waste management (MSW) has witnessed much progress in the last years with a great effort aiming to reduce associated impacts. Such efforts remain relatively limited in developing economies due to inefficient management practices. Many factors are affecting on MSW massive amounts increasing, such as population growth, economic development, limited land resources around urban areas, and inefficient waste management systems raising serious challenges and environmental concerns[1]. In many developing countries, open dumps landfilling remains the preferred method to handle the generated waste. 

Landfill Technology

Landfill have several classifications, one of them is engineered landfill which, has the capability to treat waste and produce Landfill gas (LFG). LFG produced from organic waste decomposition, a biological and chemical processes occurring after waste landfilling. The primary components of LFG are methane (CH₄) (50–60%) and carbon dioxide (CO₂) (40–50%). LFG is produced by microbial activity on biodegradable waste under anaerobic conditions. CH₄ is one of the most important greenhouse gases and has a global warming potential 21 times more than CO₂[2].

Study Area

The Republic of The Sudan (Fig. 1) area is approximately 1,886,000 km².  According to the Sudan Central Bureau of Statistics, the population of Sudan was 41.80 million people in 2018. The estimated GDP in 2018 was 40.85 billion, also the economic growth in 2018 was -2.3% and the inflation ratio was 23.9% [3].  Khartoum State (Fig. 2) is the capital of the Republic and is located in the central region of Sudan, 15°33’6.37″N, 32°31’56.68″E[4]. The current population of Khartoum in 2020 is 5,829,000, a 2.66% increase from 2019 [5]. Due to the rapidly increasing population and urbanization, waste generation increased and is currently approximately 5,100 tons of waste is generated daily in Khartoum [6].

Recently, one of the major and serious global concerns is the limitation of conventional energy resources. Sudan specifically has a critical crisis relating to fossil fuel resources, (after losing most of its oil reserves to South Sudan after separation in 2011).

Investigation Tool

In this article, LFG emissions from the Tayba Al Hasanab landfill located at Jabel Awlia locality will be investigated; This landfill starts accepting waste in 2007 with 10 years lifetime. The landfill is operated by Khartoum Municipality, and the Higher Council of Environment Urban and Rural Promotion in Khartoum state. The landfill’s total area is 0.16 km2 and various waste is buried there such as domestic solid waste which represents the bulk and slaughtering waste and medical waste in small quantities. The landfill’s maximum annual capacity is approximately 770,000 tons [8].

Several models are readily available to predict CH₄ emissions from landfills. Some of the most widely used models include the Intergovernmental Panel on Climate Change (IPCC) default and Landfill Gas Emission Model (LandGEM) version 3.02 method which was provided by the United States Environmental Protection Agency[9]. LandGEM was used to calculate future prediction emission rates for CH4 from landfill cells. For the estimation of CH4 generation from landfill cells, The Clean Air Act (CAA) defaults were used, and the forecasting period was set for 20 years. It was assumed that 2017 is the landfill closing year, and the acceptance for each year from 2007 to 2017 is 770,000 tons/year, thus the model was set to calculate the amount of CH₄ from the opening year and, until ten years after landfill closure.

Results

In the prediction model, the CH₄ generation constant (k) is specified as 0.02 year ^-1 and the CH₄generation potential (L_o) is specified as 170 M³/Mg. The CH₄ content in the LFG was specified as 50%.  The CH₄ generation rate (k), determines the rate of methane generation for the mass of waste in the landfill site, The potential methane generation capacity (L_o), depends only on the type and composition of waste placed in the landfill [10]. The estimation of CH₄ generation, emitted from the landfill cells is shown in Fig. 3. In 2017, 2020 and 2027 the total CH₄ was estimated as 21592619 m³/year, 20335162 m³/year and 17678541 m³/year respectively; The model stated 2017 as peak year of LFG generation its noticeable that the gas value decrease after the peak year due to many causes such as the landfill maturation, such amount of greenhouse gas need to be controlled because of possible of explosion and migration.

In the next article, the power generation potential from CH₄ content in LFG will be discussed.

References

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2. Fallahizadeh, S., et al., Estimation of methane gas by LandGEM model from Yasuj municipal solid waste landfill, Iran.MethodsX, 2019. 6: p. 391-398.
3. The World Bank. Sudan Country Profile.  [cited 2020 28th, FEB.]; Available from: https://databank.worldbank.org/views/reports/reportwidget.aspx?Report_Name=CountryProfile&Id=b450fd57&tbar=y&dd=y&inf=n&zm=n&country=SDN.
4. LatitudeLongitude.org. Khartoum, Sudan latitude longitude. 2015  [cited 2020 Feb, 24 ]; Available from: http://latitudelongitude.org/sd/khartoum/.
5. United Nations – World Population Prospects. Khartoum, Sudan Population 1950-2020.  [cited 2020 28th, FEB]; Available from: https://www.macrotrends.net/cities/22579/khartoum/population.
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7. Worldatlas. Sudan Map/ Geography of Sudan/ Map of Sudan. 2018  [cited 2020 Feb, 24 ]; Available from: https://www.worldatlas.com/webimage/countrys/africa/sd.htm.
8. Yadi, S.A.A.M., Assessment the Efficiency of Solid Waste Management Tayba Al Hasanab Landfill, Khartoum Municipality Sudan.
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