Analysis of a landfill gas to energy system at the municipal solid waste landfill in Gaziantep, Turkey

Abstract

This paper presents an analysis of the electricity generation from municipal solid waste (MSW), via landfill gas valorization technology, at the landfill of Gaziantep City, Turkey. Rapid increase in population, and industrial developments, throughout the world including Turkey results in larger amount of waste materials generated, increased need for energy, and adverse affects on the environment and human health. Turkey plans to produce 1/3 of its electricity demand using renewable energy sources by the year of 2023. It is recommended to use each year around 25 million tonnes of the MSW generated nationwide for a renewable energy supply. In this study, a concise summary of current status of electricity generation from a MSW landfill gas plant (via biogas harnessing) located in Gaziantep City was analyzed as a case study.

Implıcatıons: MSW management has become a major challenge in Turkey, due to the increase in the amount of solid waste, which causes negative environmental impact and results in suboptimal use of raw materials and energy. An implication of waste-to-energy technology from MSW has been applied successfully in Gaziantep, where total MSW generated has increased steadily over last 15 years. The study showed the importance and benefit of energy recovery from MSW in both economic and environmental issues in Turkey.

Introduction

Municipal solid waste (MSW) management has become a major challenge throughout the world because the amount of solid waste produced has increased in many countries with high population and limited landfill areas. In 2006, 228, 219, and 619 million tonnes of MSW were generated in the 13 countries (Denmark, Finland, France, Germany, Greece, Italy, Ireland, Luxembourg, Netherlands, Portugal, Spain, Sweden, United Kingdom) of the European Union, in the United States, and in the Organisation for Economic Co-operation and Development (OECD) area, respectively (OECD, 2008). Although, less developed countries including China and India have relatively small amount of MSW, China is expected to generate around twice as much MSW as the USA, whereas India would overtake the USA by 2030 (East Asia and Pacific Urban Development Sector Unit [EASUR], 2005). Landfilling is a relatively simple and cheap technique for disposal of solid wastes. However, poor management of solid waste in landfill areas results in environmental (contamination of soil, water, and atmosphere) and human health impact, because of the leaching of toxic components from the solids wastes in landfill areas. Many researchers indicated a significant risk of birth defects and certain cancers for the population residing around landfill areas (Sever, 1997; Johnson, 1999; Rushton, 2003; World Health Organization [WHO], 2007; Giusti, 2009, Hoornweg and Bhada-Tata, 2012). Although the evidence of adverse health outcome, on a global scale, the main disposal method of billion (10⁹) tonnes of MSW produced every year is still landfilling (DHV CR, 2001). Today, it is known that disposal of the MSW in landfill areas can be treated as a resource due to its high organic fraction and moderate energy content, which could be used for power generation (Consonni et al., 2005). Energetic MSW valorization strategies comprise incineration or production of a combustible fuel, including methane-rich landfill gas. Incineration, where the wastes are burned at high temperatures, is a relative old method. Alternatively, landfill gas containing methane and carbon dioxide produced by anaerobic digestion of MSW at the landfills can be harnessed for power generation. Landfill gas is collected using a system consisting of a number of wells drilled into the landfill and connected by a piping system. The landfill gas can be burned directly in a boiler as a heat-energy source, or it can be used in an internal combustion engine, or for electricity generation by gas turbines (Travis and Hattemer-Frey, 1989; McKay, 2002; Munster and Lund, 2010; U.S. Environmental Protection Agency [EPA], 2012; Rada, 2013; Rada et al., 2014).

Municipal solid waste (MSW) is an important environmental problem in Turkey due to the increase in population and rapid industrialization. Following the affirmation of the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) by the Turkish Great National Assembly (TBMM, Turkish acronym) in 2009, environmental concerns have received much attention. A population of 78 million people in Turkey produce massive amount of MSW, which was 25 million tonnes in the year of 2010. It is estimated that MSW generation in Turkey will be around 29 million tonnes by the year of 2023 (Melikoglu, 2013). The MSW in Turkey usually consists of wastes collected in the same waste bins (Berkun et al., 2011). Traditional way of disposing MSW in Turkey has been open dump, where the solid wastes are simply dumped without any precautions (Kocasoy and Curi, 1995). However, more than half of the MSW disposal areas in Turkey is expected to be landfilling in next 10 years (Berkun et al., 2011). Actually, Turkey generates massive amounts of municipal solid waste, because of the rapid growing consumption trends accelerated by a growing affluence of working class. The country, as a member of G20 industrialized countries with a gross domestic product (GDP) around 1 trillion U.S. dollars, need colossal amounts of energy. Considering both the vast amounts of MSW generated and the country’s energy requirements, MSW can be used as a valuable energy source. Currently, less than 1% of energy contained in Turkish MSW is recovered country (Zamorano et al., 2007; Melikoglu, 2013).

In this study, the electricity generation via methane harnessing at the landfill of Gaziantep City in Turkey is investigated. Although there are some waste service deficiencies in many Turkish cities due to the lack of technical skills, financial resources, and management of municipality authorities (Turan et al., 2009), Gaziantep City has a modern solid waste disposal landfill with a well-established MSW management for two decades.

MSW Generation and Characteristics

The total MSW generated in Gaziantep City has increased steadily over last 15 years, from 129,000 tonnes in 1992 to 428,000 tonnes in 2011, which makes the MSW management in the city very crucial (Figure 1). Table 1 shows the monthly MSW generation in Gaziantep City between 1996 and 2011 (Hengirmen, 2012). Interestingly, a decrease in the amount of MSW was observed in 2008 and 2009. The authors consider that it could be because of the global financial crisis, which was accepted by many economists as the worst financial crisis since the 1930s (Altman, 2009). In Gaziantep, increased population, industrialization, and standards of living have contributed to an increasing amount of solid waste and its consequent disposal problems (Aydogan et al., 2011). The population was 0.5 million in 1965 and 1.8 million in 2012 (Figure 2). In the 1960s, nearly 50% of the population was living in villages. However, in the last 50 years, Gaziantep transformed from an agricultural city to an industrialized city. Today, Gaziantep is a metropol with its economic structure, tourism potential, and metropolitan status. It is the center of highways and railways interconnecting the southeast of Anatolia to the west, Mediterranean, and Middle East. The population of Gaziantep is estimated to be 1.9 million by the year 2020 (Turkish Statistical Institute, TUIK). In 2007, 80% of the population in Gaziantep received sanitary waste service (Goren and Ozdemir, 2010). Before 1996, the MSW was transported out of the city and dumped in the open air without any restrictions. Waste disposal was not seen as a problem, so its management was just part of the routine work of the municipality. Nowadays, the MSW management is undertaken by Gaziantep Environmental Protection and Development Department, which is responsible for environmental monitoring at the final disposal and for material recovery. Information on the quantity of solid waste generated is fundamental to almost every aspects of solid waste management. Gaziantep’s wastes are generally classified into three major categories: (i) municipal solid wastes, (ii) industrial wastes including oil and battery, and (iii) medical wastes. However, the wastes in Gaziantep City are not usually sorted at the source, but collected in the same waste bins. Therefore, it is hard to know exact amount of recycling practiced in the city although it has been significantly increased since 1996.

Table 1. Municipal solid waste generation for Gaziantep City, between 1996 and 2011

Year	Months												Total (Ton/Year)
	Jan.	Feb.	Mar.	Apr.	May	Jun.	Jul.	Aug.	Sep.	Oct.	Nov.	Dec.
1996	—	—	—	—	—	—	—	—	—	—	—	—	129,300
1997	9,466	11,278	14,987	17,556	11,278	10,569	12,246	13,701	13,886	14,704	13,206	16,026	158,903
1998	15,649	14,235	15,801	14,331	13,110	13,173	14,761	16,008	15,075	14,385	14,654	18,296	179,478
1999	16,345	16,904	18,701	15,197	14,535	14,868	14,913	17,545	16,497	15,569	16,142	19,462	196,678
2000	19,135	19,110	19,353	16,203	16,340	14,982	15,834	18,189	17,774	17,016	16,194	21,408	211,538
2001	20,158	17,510	19,155	14,022	13,950	13,740	14,755	17,221	16,501	15,976	17,200	19,200	199,388
2002	20,153	17,474	15,831	17,976	17,039	16,990	19,784	21,353	19,839	19,005	17,404	21,573	224,421
2003	23,139	17,800	24,120	16,630	15,640	16,132	19,511	19,645	21,182	20,306	20,875	25,930	240,910
2004	26,908	25,568	23,031	19,141	18,879	19,943	21,229	22,783	22,995	21,939	23,917	28,900	275,233
2005	28,127	24,136	25,636	22,755	21,010	22,427	17,581	28,858	14,990	29,437	29,731	30,709	295,397
2006	34,667	30,801	29,774	26,579	27,767	26,267	28,703	33,624	30,941	30,350	31,487	34,031	364,991
2007	31,821	31,580	30,895	27,912	29,308	30,470	33,312	32,681	32,616	30,616	30,702	39,958	381,870
2008	37,138	35,454	31,331	24,440	24,009	27,263	28,325	30,737	31,593	27,325	26,620	34,142	358,376
2009	33,067	29,975	30,800	26,078	24,768	24,524	25,417	30,623	28,773	28,539	32,524	36,400	351,486
2010	32,524	32,624	35,109	29,261	35,109	30,909	25,308	35,485	30,515	31,309	30,193	37,209	385,555
2011	38,432	37,636	40,555	35,957	40,966	35,509	33,039	35,548	32,375	27,939	32,505	38,250	428,711
Total	386,729	362,085	375,079	324,038	323,708	317,766	324,718	374,001	345,552	344,552	320,849	383,244	4,311,380

Figure 1. Amount of waste collected in Gaziantep City, Turkey.

Figure 2. Population change of Gaziantep City between 1965 and 2012.

A review of the research results involving the quantitative and composition analyses of the MSW in Gaziantep City in recent years was presented in the Figures 3 and 4 for summer and winter seasons, respectively. The research was performed in four typical development areas in municipal surroundings: (i) housing for low-income inhabitants, who live in individual buildings, suburban, outskirts, single- and multifamily houses with coal-based heating systems; (ii) housing for medium-income inhabitants, who live in the city center, old and new buildings, combined heating systems (central and individual); (iii) housing for high-income inhabitants, who live in newly built housing estates with multifamily buildings with central heating systems; and (iv) bazaar, merchandising area, or street of shops where goods and services are sold. Figure 3 presents the results of the composition survey of Gaziantep City MSW in recent years’ summer season. During that period, considerable changes in the waste composition were observed:

• Kitchen wastes prevailed in all areas including bazaar; however, most of it was found in the area where low-income inhabitants live.

• The highest amount of paper was observed in the wastes collected from the bazaar.

• The amount of other noncombustibles was highest in the waste from low-income inhabitant living area, and the lowest in high-income inhabitant living area.

• The amount of multiple material waste including metal, garden, and glass was more comparable in all areas.

  Figure 3. Average waste composition for various areas in Gaziantep, in summer season.

  

  Figure 4. Average waste composition for various areas in Gaziantep, in winter season.

  

Figure 4 shows the MSW composition in Gaziantep in recent years’ winter season. The most striking point in this figure is a significant increase in the amount of ash, which might be attributed to the type of heating, particularly in the low-income housings. This study found that the main components of Gaziantep waste were food and paper, which constitute around 60% of overall weight in summer, whereas main components of Gaziantep wastes were food and ash in winter, constituting around 65% of overall weight in winter. These characteristics reflect the nature and lifestyle of the Gaziantep population.

Household solid wastes in the city of Gaziantep are transported by municipality-owned 6–20-m³-capacity trucks equipped with a hydraulic press. Metallic bins and containers are used to collect the municipal solid waste from the households. Typical bin sizes are 400 and 800 L. The local municipality supply containers and bins, and the residents are required to bring their solid waste into these bins within plastic waste bag supplied commercially. Solid waste recovery and recycling has been a longstanding commercial activity in Turkey (Neyim et al., 2001). With the recent investments in the recycling industry, almost all types of the plastic materials, glass, paper, and metals can be recycled at industrial levels. Despite certain limitations, in chosen districts of Gaziantep, residents collect packaging wastes such as glass, plastic bottles, cartons, and metal containers in the plastic bags/containers distributed to them by the municipality. The laborers sort them manually and compact them to reduce their size, and then they are sent to different factories to be reused and converted into useful products.

Landfill disposal area in the city of Gaziantep was an excavation with a lining system on its slopes and bottom that prevents the migration of leachate out of the landfill. The lining system consists of an impermeable, compacted clay at the bottom and geomembrane overlain by a permeable sand layer at the top (Figure 5). The integrity of the liner system is very important. In the case of such composite lining systems, protecting a geomembrane from tearing during construction and after waste placement is critical. Actually, the geomembranes are subjected to heavy loadings. Therefore, sand layer as a protective cover is required for placement of materials over the geomembrane lining to prevent damage from construction loading, and to prevent overstressing of the geomembrane lining due to subsequent waste placement. Figure 6 shows the placement of waste over the protective cover system. Landfill gas is collected using a system consisting of a number of wells drilled into the landfill (Figure 7) and connected by a piping system (Figure 8). The landfill gas is burned directly in a boiler as a heat-energy source for electricity generation by gas turbines (Figure 9).

Figure 5. Geomembrane overlain by compacted clay for lining the landfill area in Gaziantep City.

Figure 6. Placement of waste over the protective cover system.

Figure 7. Gas extraction wells.

Figure 8. Gas collection piping system.

Figure 9. Gas turbine power plant.

Electricity Generation from MSW

It is accepted that electricity consumption plays a crucial role in economic development of a country. Electricity consumption shows higher economic status of a country with a high gross domestic product (GDP) per capita (Jumbe, 2004). The most widely employed methods to estimate the electricity consumption for long-term energy demand are the autoregressive integrated moving average (ARIMA), the seasonal ARIMA (SARIMA), and the model for analysis of energy demand (MAED) (Ediger and Akar, 2007; Erdogdu, 2007). In this study, the approach proposed by Melikoglu (2013) is used to estimate electricity consumption of Gaziantep City. Estimated electricity consumption for Gaziantep City is 8538 GWhr in the year of 2018, and 13,111 GWhr in 2023. The fact is that technical and economical feasibility of electricity generation from municipal solid waste either by combustion in mass burners or methane harnessing can be estimated in a city using electricity consumption data. Landfill gas valorization technologies are promising in terms of offering electricity and heat. Such an approach does not only diversify fuel but also mitigates the environmental pollution (Tsai and Kuo, 2010). Themelis and Ulloa (2007) indicated that anaerobic biodegradation of one tonne MSW generates approximately 200 m³ methane gas, whereas 1 tonne industrial wastes generates a range of 40–80 m³. The maximum amount of generated methane during anaerobic decomposition of the organic content of MSW can be determined by eq 1 below.

(1)

Using the data shown in Table 2, and the methodology described by Themelis and Ulloa (2007), it is estimated that 1 tonne of landfilled biomass in Gaziantep contains about 190–250 kg or 1.3–1.7 kmoles of organics (C₆H₁₀O₄); hence, the reaction would generate about 4.2–5.5 kmoles or 67–88 kg methane. Melikoglu (2013) estimated the methane production from the Gaziantep landfill to be around 43–56 million m³ in 2018 and 45–58 million m³ in 2023. Fisher (1979) and Cuzin et al. (1992) stated that the calorific value of methane is around 10 kWh/m³. Thus, assuming around 25% capture and 40% electric efficiency rates, the potential electricity generation from methane, which can be harnessed at the landfill of Gaziantep City, was calculated as 34–45 GWhr for 2018 and 36–46 GWhr for 2023.

Table 2. Average moisture and organic contents and calorific value of MSW in Turkey (Melikoglu, 2013)

Parameter	Range
Moisture content (%)	65–80
Organic content (%, dry base)	50–95
Calorific value (MJ/kg)	2.0–6.0

Figure 10 shows the current flow diagram of electricity generation in Gaziantep landfill area. Total production was 2253 MWhr in the year of 2010, to be 1719 MWhr in 2011, and 2836 MWhr in 2012. Monthly base electricity production from the MSW collected in Gaziantep landfill is shown in Figure 11. It can be seen that the amount of electricity generated was much lower through the summer as an overall view. The authors interpreted that this might be attributed to the reduction in moisture content (because of the evaporation) in the landfill area, which was required for the production of methane by anaerobic bacteria in the environment.

Figure 10. Flow diagram of electricity generation in Gaziantep landfill area.

Figure 11. Comparison of electricity production.

Conclusions

The paper reports an investigation carried out to indicate a landfill gas valorization technology from the MSW landfill in Turkey. The fact is that rapid population growth and economic development, lack of technical skills, infrastructure, and financial resources, and land scarcity make the management of municipal solid waste (MSW) become one of Turkey’s most critical environmental issues. Inadequate MSW treatment in Turkey has negative environmental impact and results in suboptimal use of raw materials and energy. Currently, energy recovery from MSW is less than 1% across the country, and immediate action should be taken by the government. In this study, a concise summary of current status of electricity generation from a MSW landfill gas plant (via biogas harnessing) located in Gaziantep City was analyzed. In Gaziantep, increased population (0.5 million in 1965 and 1.8 million in 2012), industrialization, and standards of living have contributed to an increasing amount of solid waste and its consequent disposal problems. The total MSW generated in Gaziantep City has increased steadily over last 15 years, from 129,000 tonnes in 1992 to 428,000 tonnes in 2011. A review of results of the research involving the quantitative and composition analyses of MSW in Gaziantep City indicated considerable changes in the waste composition for different seasons and inhabitants having various income levels. Total electricity production from the MSW collected in Gaziantep landfill can be further used as a reference work for the analysis of municipal solid waste investments in Turkey, and their environmental impacts. Consequently, the study showed the importance and benefit of energy recovery from the MSW in Gaziantep, Turkey.

Additional information

Notes on contributors

Safak Hengirmen Tercan

Safak Hengirmen Tercan is an Assistant Professor at the Hasan Kalyoncu University, Department of Civil Engineering.

Ali Firat Cabalar

Ali Firat Cabalar is an Associate Professor at the University of Gaziantep, Department of Civil Engineering.

Gokhan Yaman

Gokhan Yaman is an Environmental Engineer at Gaziantep Metropolitan Municipality, Department of Environmental Protection and Control.