Estimation Effect of Weather Factors on Biogas Emissions Rate (Methane) from Landfill Stations in Baghdad, Iraq

Abstract


Introduction
Methane, major greenhouse gas (GHG), was estimated to have 28 times the global warming potential (GWP) of carbon dioxide (CO 2 ) over a 100-years period in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report in 2014.Methane has 84 times the global warming potential of carbon dioxide over 20-years, making it the second most significant contributor to global warming among other gases in the atmosphere (Zhao et al., 2019;Bian et al., 2021).With a fraction of 0.48 Wm -3 of the overall radiative forcing of the whole terrestrial climate, CH4 has a significant impact on global warming because it traps heat in the atmosphere more efficiently than CO2, especially in the short term (Abed and Halos, 2021;Abed et al., 2018).Total CH4 emissions are currently expected to range between 500 and 600 Tg. year -1 , with anthropogenic sources outnumbering natural sources.
Natural springs include wetlands, geological springs, lakes and rivers, termites, forest fires, and wild animals.Only 60-80% of natural CH4 emissions occur from the world's wetlands (Kleinen et al., 2021).In municipal solid waste (MSW) landfills, methane is produced as a by-product of the anaerobic decomposition of organic waste (Bogner and Matthews, 2003).One of the most serious problems facing developing countries is the improper disposal of solid waste, which is dumped haphazardly in open landfills, endangering the ecosystem and violating environmental regulations and laws (Hammash and Abed, 2022).Methane is created in landfills as a result of the decomposition of solid waste.Landfill gas (LFG) comprising approximately 50% CH4 and 45% CO2 is created under anaerobic circumstances, as the waste is broken down by aerobic bacteria and then anaerobic bacteria in the final stage (Sonderfeld et al., 2017).The product of the decomposition of municipal garbage following enteric fermentation, as well as natural gas and oil systems, is the third greatest source of methane emissions (Burns, 2015).High levels of nitrate gas concentrations can also be caused by landfills, which are caused by sewage, runoff, or contamination from human or animal waste (Al-Paruany et al., 2016).Several studies have calculated the greenhouse gas (GHG) emission potential of landfills and open dumps using various methodologies/models, according to the literature.Hannah et al, 2014 used the computational fluid dynamics CFD model to simulate the distribution of methane for several climate scenarios, which is then compared to mole fractions of methane obtained by an in situ Fourier Transform Infrared (FTIR) spectrometer downwind the direction of the prevailing wind.Assuming that only active site emissions are present, Faten et al. ( 2020) studied the vertical fluctuations of volume mixing ratio (CH4) time series data from January 2003 to September 2016 in the troposphere over six Iraqi cities at four standard pressure level (SPL) (925, 850, 600 and 300 hPa), where results from analysis of monthly mean CH4 time series data volume mixing ratio (VMR) demonstrate a considerable increase between 2003 and 2016, particularly from 2009 to 2016, with lowest CH4 levels in 2003 and highest values in 2016.According to Sohoo et al. (2021) who studied the estimation of potential for methane management and creation methane production for electrical energy generation from municipal solid waste disposal sites in Pakistan.The study aims to calculate methane emission rates from landfills in Baghdad Governorate, to study the effect of meteorological factors (temperature, wind speed and direction) on emission rates, the methane gas which produced in the landfill is a potential energy and sustainable energy source used to generate electric power for power plants in Baghdad.

Location of the Study Area
The research area (Baghdad City) is located in the Mesopotamian alluvial plain between 33.14 o and 33.25 o north latitude, and 44.13 o and 44.17 o east longitude.The general altitude varies from 30.5 to 34.85 meters above sea level.The Tigris river divides the city into two sections: right (Karkh) and left (Risafa),where Baghdad was divided into ten districts, five in Karkh and five in Al-Rusafa (Al-adili and Ali, 2005;Jawharc et al., 2022).Because Iraq is located east of the Mediterranean, it is influenced by the climate of this region, in winter it is moderate, in summer semi-arid, with hot and humid winds, although frequently accompanied of dust storms ( Hassoon et al., 2021).Baghdad Governorate has nine municipal solid waste collection stations located around the Governorate.As shown in Fig. 1 and Table 1.There are currently more than five running stations (Department of Solid Waste and Environment in the Municipality of Baghdad).The annual amount of waste for the city of Baghdad is 3304753 m 3 , according to the report of the Department of Solid Waste and Environment of the Municipality of Baghdad for the year 2021, with waste treatment in the sanitary landfills of the Nabai and Nahrawan landfills.

Data
The Iraqi Meteorological and Seismology Organization (IMOS) (provided meteorological data for this study, which included (temperatures, speed, and wind direction), as well as the yearly and monthly totals of waste solid quantities for the Governorate of Baghdad.(Department of Solid Waste and Environment in the Municipality of Baghdad).

Name location Center station Service scope Landfill
Al

Landfill Data
Annual garbage amount data collected from Department of Solid Waste and Environment in Baghdad Municipality (Baghdad Municipality) from the nine waste collection stations operating on both sides of Karkh and Rusafa in Baghdad Governorate from 2005 to 2021, can be shown in Fig. 2 illustrating the highest quantity of garbage in 2014 (11655144 m 3 ) and the lowest amount of Annual total waste was (407665m 3 ) in 2017.

Atmosphere Weather Data
The Iraqi Meteorological and Seismology Organization (IMOS) provided monthly averages of temperatures, wind speed, and direction for Baghdad Governorate from 2016, 2017 and 2018.Fig. 3 shows the monthly averages of maximum temperatures in July and August at a rate of 37C o and the lowest value of the temperature during the months of December and January at a rate of 11C o , while the maximum wind speed for the July and August ranging from 3.32m/s to 5.37 m/s.The lowest rates were reported during the January and Febrauary, with rates ranging from 2.78 m/s to 3.88 m/s throughout the same time period.Fig. 4 depicts the direction of the predominant winds during 2016 as being between 270° and 337.5°.

Methodology
Estimation of methane gas emitted by landfills in Baghdad Governorate can be calculated.and the impact of meteorological factors (temperature, wind speed and direction) on the rate of methane emissions from landfills, where biological decomposition of municipal solid waste occurs under anaerobic conditions, resulting in the production of biogas containing the methane emitted.There are several methods to calculate the rate of emissions from open landfill stations, counting carbon dioxide as the main constituent and additional gases other's including considering the Initial Landfill Gas Emissions Model (LandGEM).In 1996, the second edition of the IPCC Guidelines was published (default method) and (Kaushal and Sharma, 2016).In Baghdad Governorate, the default method was used to estimate methane gas emissions from landfills, where solid waste data was generated in waste collection stations which are distributed on both sides of Karkh and Rusafa from the Department of Solid Waste and Environment of the Municipality of Baghdad.In addition, the annual and monthly sum of waste quantities was taken from (2016, 2017 and 2018).

Anaerobic Degradation
Organic elements are transformed into methane and carbon dioxide, as well as small amounts of biomass and energy, when the waste is buried in oxygen absence landfills.The anaerobic decomposition process has three stages (Themelis and Ulloa, 2007).1. Hydrolysis: Complex organic matter (proteins, lipids, carbohydrates, and so on) is hydrolyzed by fermentative bacteria into simple soluble organic molecules like amino acids and glucose.Where hydrolysis is a slow process that occurs through anaerobic degradation, where the kinetics of the process regulates all reactions, thereby slowing down all (Janusz et al., 2017).2. Acetogenesis: Acidifying bacteria convert hydrolysis' end products into volatile fatty acids, CO2, and H2.After then, the acetogenic bacteria change.Acetic acid, CO2, and H2 are examples of volatile fatty acids.Acetic acid, propionic acid, butyric acid, and ethanol are the most common acids created.During this phase, there is a high concentration of hydrogen-producing and hydrogen-consuming bacteria, as well as bacteria that reduce nitrates and sulfate.Below is an example of the reaction (Janusz et al., 2017).
C6H12O6 → 2C2H5OH + 2CO2 (1) 3. Methanogenesis: Methane is produced at this stage by methanogenic bacteria, which break down acids into methane and carbon dioxide or reduce carbon dioxide with hydrogen.A representative reaction is shown.below.
(3) Acetogenic and methanogenic bacteria are extremely sensitive, strictly anaerobic, and substrate-specific in the second and third phases (Raga and Cossu, 2014).

Land GEM Model
Using equations ( 4) and ( 5), Land GEM methods were used to estimate total gas emissions from the landfill rate of municipal solid waste landfills, which largely consist of (methane and carbon dioxide).andnon-methane organic chemicals.To calculate annual methane emissions over a usersupplied time period (Ghasemzade and Pazoki, 2017;Anh et al., 2021).

Default method
To estimate methane (CH4) emission rates from the organic fraction of municipal solid waste (i.e.paper and cardboard, food, grass and leaves, textiles and wood) placed in landfills, the IPCC default technique was employed.The methodology is based on theoretical gas production from the mass balance equation, and it assumes that all potential CH4 emissions from garbage are released in the same year as the waste is thrown.This default method can be used to create reasonable annual estimates of methane emissions if the composition and volume of garbage discharged remains constant or varies slowly over several decades.The default IPCC methodology, however, will not offer an accurate trend of emissions because the amount and composition of rubbish changes fast over time.(CH4) emissions from waste disposal sites are assessed using equation ( 6) (Sohoo et al., 2021).Ox: Oxidation factor (fraction, default is 0).Equation ( 7) can be used to compute the fraction of degradable organic carbon DOx.According to the report of the Department of Solid Waste and Environment in the Municipality of Baghdad, the percentages of organic materials, materials, plastic, paper, metal, and glass as a general average for the Governorate of Baghdad are shown in Table 2 which shows the cumulative rate of daily excretion per capita for Baghdad Governorate The fraction DOF dissimilated can be calculated by Equation ( 8).
Where T: Atmosphere Temperature of area.
Table 3 shows the methane correction factor (fraction) for the IPCC document

Annual Behavior of Rate Methane Emission
Fig. 5 illustrates the methane emission rate over the study period (2016, 2017 and 2018) against the total annual amount of waste, with the highest amount of methane gas rate (0.0459 GgYr -1 ) during 2018 and the lowest amount of methane gas rate 0.0077 GgYr -1 in 2017, while the annual total amount of waste was 2421808 m 3 and 407665 m 3 in 2018 and 2017 respectively.

Monthly Behavior of Rate Methane Emission
Using Equation ( 6), the rate of methane gas emissions emitted from landfills in Baghdad Governorate was estimated.Methane gas emissions from landfills are shown in units (Gg/month), Table 4. shows the highest methane gas emissions in the months June, July and August for the study period at a rate ranging from 0.0024 to 0.00762 Gg/month, as well as the lowest emissions in the months January, February, September and December for the period of study at a rate ranging from 0.0024 to 0.0007298 Gg/Month and shows the monthly behavior of methane.During the study period, the highest gas concentrations occurred during the summer, while the lowest concentrations occurred during the winter, because it has been calculated that a 3.4C o temperature increase might result in up to 78% increase in CH4 emissions.

Effect of Weather Element on Methane Emission Rate
Assessment of the impact of weather factors on methane emissions from landfill stations for the years (2016, 2017 and 2018).

Temperature (C o )
Table 5 shows the highest and lowest methane gas emissions (Gg/ Month) from open landfill stations.During the years 2016-2018, the highest levels of methane gas emissions occurred predominantly in July and August, when average temperatures in those months ranged from (36 C o -38 C o ), while the lowest temperature levels occurred in January and February (10 C o -13 C o ) because it has been calculated that a 3.4C o temperature increase might result in up to 78% increase in CH4 emissions

Wind speed and directions
Table 6 shows the highest and lowest levels of methane gas emissions from landfills.Where the highest rates of methane emissions for the months of August and July ranging from 0.0027 to 0.005181136 Gg/month while the wind speed is about 3.32 m/s to 5.37 m/s.The lowest rates were in the January and February ranging from 0.000633758 to 0.000391276 with wind speed rates that ranging from 2.78 m/s to 3.88 m/s.We may extrapolate that the months with the highest wind speeds have the highest levels of methane emission, while the months with the lowest wind speeds have the lowest levels of methane emission.The prevailing wind direction during the years 2016, 2017 and 2018 was 270 o -337.5 o through which the direction of methane emission is determined and in which places the emitted methane concentration will decrease with the direction of the wind.

Estimation of the Amount Electrical Energy Produced by Landfills Station Garbage
Equation 9 can be used to calculate the possibilities of generating electrical energy from methane gas produced at waste sites in Baghdad Governorate.After converting landfill stations to typical released gas to be collected and use as sustainable electrical energy (Ep) after leachate treatment (Rodrigue et al., 2018).
Where Ep: sustainable electrical energy.LHVMethane: is the lower calorific value of methane and is given by 37.2 (MJ/m 3 ).QCH4 annual methane production in the year of the calculation (m 3 /year).
: is the electrical conversion efficiency for a given internal combustion engine at 33%.

3.6:
is the conversion factor from MJ to kWh.The amount of electrical energy (kWh/year) that could be obtained from the methane emission rate was calculated, as shown in Table 7.

Conclusions
It is feasible to collect biological gases from landfill sites in Baghdad governorate, containing gases (methane and carbon dioxide) in particular, with very low amounts of other gases (hydrogen sulfide (H2S), nitrogen, ammonia, sulfur dioxide, and carbon monoxide) in general.The amount of methane gas emitted from landfills in Baghdad Governorate was determined using the approach based on waste quantity data collected from the Department of Solid Waste and Environment in the Municipality of Baghdad.Default Method of the IPCC Guidelines, The maximum amounts of methane emissions were in July and August during 2016-2018, at a rate of 0.002905Gg/Yr, and the majority of them were in months whose temperatures ranged between 36C o and 38 C o , while the minimum amounts of methane emissions were in January and February during 2016-2018, at a rate of 0.001154 Gg/Yr, and the majority of them were in months whose temperatures ranged between 10 C o and 13 C o .The maximum amounts of methane emissions were in July and August during 2016-2018, at a rate of 0.002905Gg/Yr, and the majority of them were in months whose wind speed ranged between 3.322 m/s and 5.377m/s, while the minimum amounts of methane emissions were in January and February during 2016-2018, at a rate of 0.001154 Gg/Yr, and the majority of them were in months whose wind speed ranged between 2.781 m/s and 3.388 m/s, during the years 2016, 2017 And 2018, the prevailing wind direction was about 270 o -337.5 o .Methane from landfills can be used as a source of renewable energy.During the years 2016, 2017 and 2018, then computed the amount of electrical energy (kWh /year) that may be obtained from rate emission methane, arriving at 57.666kWh -105.661kWh.

Fig. 2 .
Fig.2.Annual total of solid waste amount at years 2005 -2021 for Baghdad Governorate
Where A: percentage MSW i.e. paper and textile.B: percentage of MSW that is yard waste, park waste or another non-food organic putrescible.C: percent MSW which is food waste.D: percentage of MSW in wood or straw.

Fig. 5 .
Fig.5.Annual average of methane gas emitted from landfill stations and total amount of solid waste for Years 2016, 2017 and 2018

Table 2 .
The cumulative average daily emission per person Baghdad Governorate

Table 4 .
Rate Methane Emissions Estimate from landfill

Table 5 .
Maximum and minimum rate methane emission and average temperature effect

Table 6 :
Maximum and minimum rate methane emission by wind speed and direction effect

Table 7 .
Estimation of the amount of electrical energy produced by landfills station garbage