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Waste to energy technologies for municipal solid waste management in Gaziantep
Renewable and Sustainable Energy Reviews 54 (2016) 809–815
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Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser
Waste to energy technologies for municipal solid waste management in Gaziantep Alperen Tozlu 1, Emrah Özahi n, Ayşegül Abuşoğlu 2 University of Gaziantep, Faculty of Engineering, Mechanical Engineering Department, 27310 Gaziantep, Turkey
art ic l e i nf o
a b s t r a c t
Article history: Received 2 April 2015 Received in revised form 1 September 2015 Accepted 21 October 2015
Landfill gas (LFG) which is produced by means of municipal solid waste (MSW) treatment activities can be considered as a source of greenhouse gases, including mostly methane. Therefore its management plays an important role. During the process of methane production in MSW plants, LFG is collected, treated and then used for power production purposes. Although there have been many technologies existed, incineration and landfilling methods are mostly preferred all over the world today due to their high energy production potentials. The increasing amount of solid waste arising from municipalities and other sources and its consequent disposal have been the major environmental and economic problems in Turkey. Furthermore, providing more effective and eco-friendly solutions has been a key point for Turkey while being a candidate country for European Union (EU) accession. In this paper, a brief overview on recent technologies and methods applied to MSW management in the world is presented. Current research studies accessed on the literature on MSW are outlined. Moreover, recent MSW management in Gaziantep metropolitan city is displayed with the existing method which produces LFG for power production. Some concluding remarks and recommendations are presented for future developments in MSW management. & 2015 Elsevier Ltd. All rights reserved.
Keywords: Municipal solid waste Landfill gas Waste to energy Gaziantep Power
Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Recent studies on MSW management . . . . . 3. WTE technologies in the world and Turkey . 4. MSW management in Gaziantep . . . . . . . . . 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1. Introduction Municipal Solid Waste (MSW) known as trash or garbage consists of food waste, paper, cardboard, plastics, PET, glass, textiles, metals, wood and leather, nappies, slug, ash, etc. Urbanization level, population growth and technological changes support
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Corresponding author. Tel.: þ 90 342 3601200/2567; fax: þ90 342 3601104. E-mail addresses: [email protected] (A. Tozlu), [email protected] (E. Özahi), [email protected] (A. Abuşoğlu). 1 Tel.: þ90-342-3601200/2524; fax: þ 90-342-3601104. 2 Tel.: þ90-342-3601200/2576; fax: þ90-342-3601104. http://dx.doi.org/10.1016/j.rser.2015.10.097 1364-0321/& 2015 Elsevier Ltd. All rights reserved.
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to increase MSW generation in developing countries. Landfill gas (LFG) which is produced by means of MSW treatment activities can be considered as a source of greenhouse gases, including mostly methane. Thus, all treatment activities of MSW can also be turned into an opportunity for a sustainable production of energy which is known as "waste-to-energy" (WTE). Due to the moisture content of MSW, its lower heating value varies between 5 and 20 MJ/kg. In the same manner, International Energy Agency (IEA) reported that a ton of MSW should have a calorific value between 8 and 12 MJ/kg for an effective energy generation [1]. In previous years, unsanitary landfill activities, open dumping and open incineration methods were common solutions to remove
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MSW from city centers without considering their energy potential and environmental impact. Rapid increase in population and industrial developments has led to findings of new technologies alternatively to these conventional insufficient methods for disposal of MSW. Besides, WTE technologies have become popular research area for governments, researchers and entrepreneurs. There are three fundamental types of WTE technologies [2]: (i) thermal conversion methods (incineration, pyrolysis, and gasification), (ii) biochemical conversion, (iii) landfill. In thermal conversion technology, the mostly used method is incineration. “Incineration” method is mainly the waste destruction in a furnace by controlling combustion at high temperatures. By the incineration method, approximately 70% of total waste mass and thus 90% of total volume can be reduced [3]. Incineration process is completed in three steps which are incineration, energy recovery and air pollution. After incineration process, air pollutants such as SOx, COx, and NOx which are harmful for human health occur. The process is performed between 750 and 1000 °C. “Pyrolysis” is another method in which thermal waste treatment is taken place in an oxygen free environment. There are three types of pyrolysis methods which are conventional pyrolysis (550–900 K), fast pyrolysis (850–1250 K), and flash pyrolysis (1050–1300 K). The third thermal conversion method, “gasification”, is a process that converts MSW into CO2, CO and H2O, which occurs by reacting MSW at high temperatures ( 4700 °C), without combustion, with a controlled amount of oxygen and/or steam [2]. Due to reactor design and operational parameters, gasification process generates other higher hydrocarbons (HC) besides methane. The obtained combustible gas includes CO, CO2, CH4, H2, H2O, some inert gases, trace amounts of higher HCs and various contaminants such as small char particles, tars and ash. The second main group of WTE technology is biochemical conversion. It is much more eco-friendly when compared with others. Biochemical conversion is primarily based on the reaction of microorganism enzymes. Biochemical conversion method is divided into two subgroups as “Anaerobic Digestion” and “Composting” [2]. In “Anaerobic Digestion”, MSW is collected in an oxygen free environment, which is a combination of series of biological processes in which microorganisms break down to biodegradable material. This process which occurs at almost 65 °C decreases the amount of waste and produces biogas for combined heat and power or as a transport fuel. The rest of the production such as inorganic and the inert waste are either incinerated or gasified. By means of this process, 2–4 times as much methane may be produced in 3 weeks when compared with methane production with landfill process in which 6–7 years are needed for 1 t of MSW. On the other hand, “Composting” is a biological decomposition of biodegradable solid waste under predominantly aerobic conditions. It is a natural process of recycling decomposed organic materials into a rich soil known as compost [2]. One of the mostly used and practical technology, a third main group, for WTE today is “Landfilling” which is a soil-based waste disposal technique that uses engineering principles to confine solid waste to smallest area possible and reduce it to the lowest allowable volume in sanitary landfill [4]. Sanitary landfill can be defined as a scientific dumping of MSW using an engineering facility which requires detailed planning and specifications, careful construction and efficient operation [5]. The schematic representation of a typical landfilling process with its steps [3] is shown in Fig. 1. Although landfill is the most common waste treatment techniques in the world, the developed countries prefer to reduce their MSW by using incineration technology due to reduction of approximately 70% of total waste mass and thus 90% of total volume. However, it is a fact that mass burning of MSW creates major environmental problems due to pollutant discharges.
Site Selection
Specific land preparation
Layerwise sanitary land filling
Final soil cover and maturing Compost segregation
Leachate pumping out Combustible gas Water treatment
Final compost Gas engine
Treated water
Electric generator
Fig. 1. Flow diagram of MSW plant based on sanitary landfill [3].
Therefore the best alternative technique for energy recovery for MSW is controlled methane production at landfills. The more details about the advantages and disadvantages of WTE technologies are given in Table 1. In this paper, an overview about WTE technology in the world as well as that in Turkey is presented. Some important current studies on MSW management are outlined. Then, recent MSW management in Gaziantep metropolitan city is displayed with the current WTE technology applied, giving some concluding remarks and recommendations for future developments in MSW management.
2. Recent studies on MSW management Despite of these WTE plants operated for many years, there are still several MSW management problems in the world and the current technology is needed to be developed. For this reason, many investigations are performed to improve the current WTE technologies to increase the amount of generated energy as well as decreasing the amount of MSW. MSW management is crucially important to organize the current WTE plants efficiently and ecofriendly. In this respect, there are also many studies on MSW management for local regions. Many of these studies are related with MSW management and policy of existing systems in local regions presenting the recent portrait and giving further recommendations for developments and/or modifications. Metin et al. [6] presented a general overview of MSW management in Turkey during the last decade. They indicated that the composition of recovered material shows some variations depending on the source (commercial, residential and mixed) and the season of the year, and the majority of the material collected. They clarified that initial investment to set up large-scale collection and recovery schemes still remained to be the major barrier that the municipalities have to overcome.
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Table 1 Advantages and disadvantages of WTE technologies [2]. Technology
Advantages
Disadvantages
Thermal conversion Incineration
– Most suitable for high calorific value waste – Units with high throughput and continuous feed can be set up – Thermal energy for power generation or direct heating – Relatively noiseless and odorless – Low lands are required – Can be located within city limits, reducing transportation costs – Hygienic – Production of fuel gas/oil, which can be used for various – purposes – Control of pollution superior as compared to incineration – Energy recovery with production of high grade soil conditioner – No power requirement for sieving and turning of waste pile – Enclosed system enables trapping the gas produced for use – Controls GHG emissions – Free from bad odor, rodent and fly menace, visible pollution and social resistance – Compact design needs less land area – Net positive environmental gains – Can be done in small scale – Least cost option – Gas produced can be utilized for power generation or direct thermal application – Skilled personnel not required – Natural resources are returned to the soil and recycled – Can convert marshy lands to useful areas
– Least suited for aqueous, high moisture content, low calorific value and chlorinated waste – Toxic metal concentration in ash, particulate emissions, SOx,NOx, chlorinated compounds, ranging from HCL to dioxins – High capital and O&M costs – Skilled personnel required – Overall efficiency for small power stations is low
Pyrolysis/ gasification
Biochemical Conversion
Landfilling
Magrinho et al. [7] introduced the basic principles of MSW management in Portugal. They stated that it was needed to give a considerable amount of effort in order to obtain real and significant positive evolution in MSW prevention, reduction and recovery. Turan et al. [8] showed a brief history of the legislative trends in Turkey for MSW management. They claimed that primitive disposal methods such as open dumping and discharge into surface water had been used in various parts of Turkey although strict regulations on MSW management were in place. They also clarified that 70.57% of the total amount of MSW was disposed of without any control. Manaf et al. [9] studied on MSW management in Malaysia. They emphasized that a new institutional and legislation framework has been structured with the objectives to establish a holistic, integrated, and cost-effective MSW management system, with an emphasis on environmental protection and public health, increasing the efficiency of MSW management towards 2020. Aydoğan et al. [10] determined and explained the MSW management, solid waste quality, collecting method of solid wastes, transportation and waste disposal options in Gaziantep. Oteng-Ababio et al. [11] studied on a case study in new MSW technologies in Accra city in Africa. They stated that rigorous evaluation of all waste management options was the best way to safeguard against ill-fated investments and toward meaningful advancement in sound MSW management in the long-term. Herva et al. [12] presented the results of the environmental evaluation of MSW processes in Portugal in the period 2007–2011. They concluded that the environmental gains of MSW were higher than the environmental impacts, and highlighted that the electricity generated in the energy recovery plant was remarkable. On contrary to all these, Fobil et al. [13] discussed research experiences in Accra, Ghana for utilizing MSW for energy generation. They concluded that MSW had a low energy recovery efficiency,
– Net energy recovery may suffer in waste with excessive moisture – High viscosity of pyrolysis oil may be problematic for its burning and transportation
– Unsuitable for wastes containing less organic matter – Requires waste segregation for improving digestion efficiency
– – – – – –
Surface runoff during rainfall causes pollution Soil and groundwater may get polluted by the leachate Yields only 30%–40% of the total gas generated Large land area required Significant transportation costs Cost of pre-treatment to upgrade the gas to pipeline quality and leachate treatment may be significant – Spontaneous explosion due to methane gas build up
approximated at 40% recovery, due to high equipment installation and plant maintenance costs. Leachate is an important problem in a sanitary landfill area such that leachate water may diffuse into underground water. Hence it is very crucial for public health and this problem have to be overcome. Ağdağ [14] presented a general overview and compared old and new MSW management practices in Denizli. It was claimed that there were still some deficiencies in the new MSW management system such as no leachate treatment and poor source separation collection. The content of MSW also plays an important role in MSW management and for efficiency of energy production. In this respect, many studies can be found in selection, sorting and segregation processes of MSW. Horttanainen et al. [15] collected Finnish studies concerning the composition and energy content of mixed MSW (organic waste, paper, plastic and cardboard, etc.), which is incinerated for energy production. They found that in mixed MSW, the renewable share of the energy content could be significantly lower than the general assumptions (50–60%). They also claimed that the low share of biowaste in mixed MSW decreases the moisture content of the waste, increasing the heating value. Besides of this, it was also found that high share of plastic increases the heating value and the nonrenewable share of energy in the waste material. Also the improvement of paper and cardboard recycling is seen to decrease the share of renewable energy in mixed MSW. The available WTE techniques are compared by many scientists regarding the waste material, capacity of landfill area, etc. OjedaBenitez and Beraud-Lozano [16] performed an analysis for sanitary landfill and the uncontrolled dump in four cities of Mexico. They pointed out the disadvantage of uncontrolled dump due to pollutants and a serious threat to human health, and proposed a development
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and an extensive construction of integrated sanitary landfills. Bovea et al. [17] performed a case study on environmental assessment of alternative MSW management strategies in Spain applying LCA methodology. They found that biogasification and energy recovery achieved better environmental performances than landfill without energy recovery. Cheng and Hu [18] presented a perspective on MSW discussing the major challenges in expanding WTE incineration in China in terms of capital and operational costs, equipment corrosion, air pollutant emissions and fly ash disposal. They claimed that WTE incineration gave greater contribution for supplying renewable energy in China. Kanat [19] presented the situation of MSW management in İstanbul considering current requirements and challenges in relation to the optimization of İstanbul's MSW collection. It was stated that there was a great need to reduce the volume of solid waste in Istanbul and recommended to design a waste-management system according to capacity. It was mentioned that landfilling technique was not a proper solution for metropolitan cities, such as İstanbul. The WTE techniques are also considered in terms of their emissions. Lino and Ismail [20] studied on the energy savings and the avoided emissions of CO2 to the atmosphere as a result of recycling and production of LFG from landfills in Brazil. It was mentioned that the solid waste deposited in landfills without treatment impacted on the public health. And they also stated that the anaerobic degradation of the organic matter to produce LFG alleviated the ambient from the CO2 and CH4 emissions otherwise liberated to the atmosphere. Udomsri et al. [21] presented an evaluation of the potential of MSW incineration for climate change mitigation and promotion of biomass-based electricity production in a more sustainable direction in Thailand. They resulted that MSW incineration had the ability to lessen environmental impact associated with waste disposal, and it could contribute positively towards expanding biomass-based energy production. It was emphasized that hybrid cycles could be used to improve system performance and overall electrical efficiency of conventional incineration. Akinci et al. [22] performed a future planning for the waste management in Izmir, Kula, and Usak. They proposed methane production in Izmir for the biological degradation of Izmir green wastes, and composting method for Kula and Uşak. Arafat et al. [23] studied on the environmental impacts for MSW treatment processes with energy recovery potential using life cycle assessment (LCA) methodology. They claimed that it was the best to recycle paper, wood and plastics; to anaerobically digest food and yard wastes; and to incinerate textile waste. In view of the treatment processes, anaerobic digestion and gasification were found to perform better environmentally than the other processes, while composting had the least environmental benefit. Melikoğlu [1] estimated the potential of electricity generation via MSW combustion and methane harnessing at the landfills of 81 Turkish cities. It was claimed that the energy recovery from MSW is less than 1% countrywide. Melikoğlu [1] preferred incineration technique for further methods for energy production from MSW. Phillips and Mondal [24] performed a mathematical model of sustainability of options for MSW disposal in India. They clarified that gasification may be the best potential sustainable option for MSW disposal due to positive impacts overall for the local environment and community. Hossain et al. [25] reviewed the types of MSW in Bangladesh. They stated that WTE incineration was playing a fundamental role for renewable energy production reducing space for new landfills. However, low calorific value and high water content were pointed out to deficit the power generation from MSW incineration.
3. WTE technologies in the world and Turkey It can be stated that there are many WTE plants which have been constructed in the world since 1990's. In 1990, 394 trillion Btu of energy which was produced from MSW was consumed in
USA. On the other hand, some of energy demand in Japan was provided from 102 waste incineration plants in the end of 1991. Also there were many WTE plants in Germany in the 90's. In United Kingdom, the 70th report by the Royal Commissions on Environmental Pollution emphasized the importance of modern technology in MSW plants [2,26]. Agricultural biomass is used to generate electricity in Poland. At the end of 2012, there are 29 agricultural biogas plants in Poland with an average installed capacity of 1 MW [2,27]. Agricultural biomass has also been used in many African countries including Ghana to produce decentralized rural energy. The total output is around 12.5 kW electric power using two generators rated 5 kV A and 7.5 kV A. The produced electricity is supplied to the community using a local grid of 230 V for 12 h per day [2,28]. In Southeastern Asia, Malaysia has also been very active in MSW techniques. Methane emissions from Malaysian landfills for 2010 were equivalent to 2.20 109 kW h of electricity [2,29,30]. In Europe, Italy has many anaerobic co-digestion plants ranging between 50 kW and 1 MW [2,31]. Thessaloniki in Greece has been following the integrated solid waste management and energy production, and now biocell technology is used in order to utilize the better biogas production using innovations [2,32]. Also, in Singapore, food waste is used as an alternative option for the energy recovery and many policies are developed for MSW technology and management [2,33]. Canada has also accelerated the MSW technology to convert MSW to energy by means of designed various systems to recover the energy of MSW. They produce 134.6 MW h per year of surplus energy [2,34]. Although the historical background of WTE technology dates back to 1990's in the world and the most of energy needed in Turkey has been imported, the efficient technology in MSW management could not be achieved in Turkey until 2002. The developments in WTE technology have been accelerated in Turkey over the last two decades by means of the government's recent progress in the frame of Turkey's 2023 vision. 30% of the demand of electricity in Turkey is planned to be met from renewable energy sources by 2023. The increasing amount of solid waste arising from municipalities and other sources and its consequent disposal have been the major environmental and economic problems in Turkey. These problems enforce MSW to be one of the renewable energy sources in Turkey such that 25 million tons of MSW is produced annually nationwide. Landfilling technique which is used to generate energy from MSW is a primary waste management option in Turkey. However, this technique has some environmental problems such as anthropogenic methane and carbon dioxide emissions, water pollution due to leachate production, etc. According to the European Union (EU) landfill directive (1999/31/EC), the amount of biodegradable organic waste deposited in landfills should be decreased by 65% of the 1995 level by 2016. On contrary to this, landfill technique is more eco-friendly one when compared with incineration technique [1]. Most of people which are about 83% of the population in Turkey receive MSW services, as well as this value is about 99% in municipality area, but still there are more than 2000 open dumps in Turkey [8,35]. According to Turkish Statistical Institutes database, 176,300 GW h of electricity was produced in 2006 but only 0.2% of the produced energy was provided from renewable energy sources and waste [35] whereas the consumption of electricity was about 143,070 GW h in 2006. In 2013, there was a significant increase in energy production from renewable energy sources and waste such that 4.2% of 240,154 GW h electricity was produced from the mentioned sources whereas the total electricity consumption was 194,923 GW h. According to 2013 values, there were 80 sanitary landfills, 2 incineration plants and 5 compost plants in Turkey. The number
A. Tozlu et al. / Renewable and Sustainable Energy Reviews 54 (2016) 809–815
of sanitary landfills in Turkey is planned to increase 130 at the end of 2017. The WTE techniques applied in Turkey by 2012 is summarized in Fig. 2. According to Turkish Statistical Institute values [35], 59.9% of MSW was disposed in municipality sanitary landfills, 0.11% of MSW was combusted with incineration, 1.15% of MSW was disposed by using a recycling method, and 37.8% of MSW was accumulated by means of municipality dumps in Turkey by 2012. The rest of waste (0.64% of MSW) was disposed with other methods. The situation of MSW management in Turkey with comparisons of other regions is tabulated in Table 2 [35,36]. As can be seen from Table 2, sanitary landfill for disposal of MSW is more preferable technique in Turkey. Besides, less popular technique in Turkey is seen to be incineration one as can be noticed from the table. Although incineration technique in Europe is a common method, it is not favorable in North America. In North and Latin America, sanitary landfill is mostly used technique. On the other hand, open dump disposal method is very common in Asian and African countries.
4. MSW management in Gaziantep Gaziantep, which is located in the southeast region of Turkey, is the 6th biggest city as a population which is about 2,000,000. Total land area of Gaziantep is 7642 km2. With the total consumption of electricity, Gaziantep is on the 11th rank in Turkey [35]. Annual electricity consumption per capita is 2560 kW h in Gaziantep. The reason of this high electricity consumption is clearly due to dense population and industrial facilities in the city. Over the last decades, industry in Gaziantep has developed very rapidly, especially in plastic, textile, food, carpet and package industries. In Gaziantep, there are some private companies which produce their own electricity using natural gas, fuel oil, LFG and also hydropower. The installed power capacities of these companies are shown in Fig. 3 [37]. Among this distribution, LFG produced from MSW plays an important role for energy production in Gaziantep, in terms of WTE concept. As the historical background of MSW management in Gaziantep is considered, MSW was collected by Gaziantep
813
Metropolitan Municipality in an unsanitary landfill until 1996, for only disposal purpose at Beylerbeyi location which was too close to the city center. After 1993, Gaziantep Metropolitan Municipality has started to construct a sanitary landfill plant with an installed power capacity of 5.66 MW for both disposal of MSW and energy production from produced LFG in Mazmahor, Uzundere under the grant of Southeastern Anatolia Project (GAP). This constructed sanitary landfill has 32.3 ha solid waste storage area and also 10,000,000 m3 solid waste capacities which will fulfill the need until 2046 [10]. This plant produces 1.25% of total power demand of Gaziantep. Average percentage compositions of MSW in Gaziantep and its comparison with other metropolitan cities is given in Table 3 [6,10,14]. Fig. 4 shows the schematic representation of Gaziantep Municipal Solid Waste Power Plant (GMSWPP). In GMSWPP, LFG is created during the anaerobic decomposition of organic substances in domestic solid waste, industrial, and medical wastes. The total MSW carried to GMSWPP is 1500 t daily. All wastes collected in GMSWPP are subjected to mechanical segregation of plastic, metal and glass, and then rest of MSW is sent to sanitary landfilling area. On the other hand, medical waste is sterilized first as a pretreatment and then sent into landfilling area. MSW which is buried underground in landfilling area is led to produce LFG for months. The produced LFG from the storage area is collected from 114 high density polyethylene (HDPE) funnels with a diameter of 800 mm, which are underground in 8–41 m depths. The collected LFG is then transferred to 6 manifold stations. If temperature of LFG is higher than 40–45 °C, it is cooled through a heat
8.6 9.73 20
8 6.7
5.66
24.63
189
21 25
37
Sanitary Landfill
49
Incineration Recycling Open Dump Open Burning
49
Karkam1ş Dam and HEPP (HE)
Goren 2 TPP (NG)
Goren 1 NGPP (NG)
Gülsan Syn. Man. NGPP (NG)
Başp1nar CU (FUELOIL)
Naksan EPP 2 (NG)
Naksan CU (NG)
Melike Tex. NGPP (NG)
Selçuk Tex. NGPP (NG)
Naksan EPP (NG)
Gürteks Tex. NGPP (NG)
Gaziantep MSW Plant (LFG)
Other HEPP: Hydroelectric Power Plant, TPP: Thermal Power Plant NGPP: Natural Gas Power Plant, CU: Cogeneration Unit EPP: Energy Power Plant, SEPP: Solar Energy Power Plant
Other Fig. 2. Distribution of WTE techniques applied in Turkey.
Fig. 3. Distribution of energy production in MWe in Gaziantep.
Table 2 Worldwide MSW management in 2012 [35,36]. Region
Sanitary landfill (%)
Incineration (%)
Recycling (%)
Open dump (%)
Open burning
Other (%)
Turkey Africa Asia Europe North America Latin America
59.9 29 31 27 91 59
0.11 2 5 14 0 2
1.15 4 8 11 8 3
37.8 47 51 33 0 31
0.4 9 2 12 0 4
0.64 9 3 3 1 1
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exchanger by means of chilled water in the direction which is denoted with blue arrows in Fig. 4. LFG which is under 40–45 °C is sucked into tandem demisters/filters in order to eliminate water and particulates such as aluminum, ash, etc by using blowers having the operating vacuum pressure of 6 kPa. There is one flare stack mounted at the exit of blowers in order to drain excess LFG at any emergency case. The collected water is sent back to a drain tank. The filtered LFG sucked through four pipelines is collected in A/C tanks for desulphurization process. At the exit of the A/C tanks, if the operating pressure exceeds 14.5 kPa gage, excess LFG is sent back to the beginning of process pipeline by using a pressure control valve. At the same time, volumetric content of LFG are measured and also recorded on a control panel. At any instant, the average volumetric values of the components of LFG are given in Table 4. The percentage of methane in LFG according to the monthly distribution in 2014 is also shown in Fig. 5. As can be seen from the figure, the average volumetric percentage of methane is nearly 45. Moreover, the operation is stopped automatically when methane content is decreased below 38% and oxygen is increased above 6%. The flow rate, operating pressure and temperature data are measured at 7, 15 and 5 stations, respectively throughout the process pipeline. The volumetric flow rate of LFG is measured 17.5 m3/min through the main pipeline. After the reduction of H2S content in LFG to 100–120 ppm, it is then pumped into three 1.13 MW Janbacher-4 type gas engines coupled with generators to produce electricity. The exhaust gas is recorded as nearly 550–600 °C at the end of the process. Due to the increasing amount of MSW in Gaziantep, two 1.13 MW Janbacher-4 type gas engines will be
constructed to the existing system in order to increase the capacity of the power plant. Fig. 6 illustrates the monthly energy production in MW h in the power plant. The average energy production for each month is almost 1650 MW h which satisfies the energy demand of 2000 households in Gaziantep.
5. Conclusions In Gaziantep, there was only one unsanitary landfill which had serious environmental problems because of uncontrolled gas Table 4 Average volumetric composition of LFG produced in GMSWPP. Components
Chemical formula
(%) Dry volume
Methane Carbon dioxide Carbon monoxide Nitrogen Oxygen Hydrogen Hydrogen Sulfur
CH4 CO2 CO N2 O2 H2 H2S
45–53 30–32 1–5 2–6 3–5 3–7 0–2
CH4 60 50 40
Table 3 Composition of MSWc in 6 metropolitan cities in Turkey [6,10,14].
% 30
Cities
Organic
Paper/cardboard
Plastic
Metal
Glass
Others
Istanbul Izmir Bursa Gaziantep Adana Mersin
43 46 53.1 41.6 64.4 63
7.8 12 18.4 6.1 14.8 18.4
14.2 12 11.6 4.8 5.9 6.7
5.8 3 3 1 1.4 1.3
6.2 4 3.4 7.1 3.1 3.1
23.1 23 10.5 39.5 11.4 7.6
20 10 0
N FE B M A R A PR M A Y JU N JU L A U G SE P O CT N O V D EC
(%) Compositions
JA
814
Fig. 5. Monthly methane content in LFG produced in GMSWPP.
Fig. 4. Schematic layout of GMSWPP.
A. Tozlu et al. / Renewable and Sustainable Energy Reviews 54 (2016) 809–815
JA
N FE B M A R A PR M A Y JU N JU L A U G SE P O CT N O V D EC
MWh
ENERGY PRODUCTION 2000 1800 1600 1400 1200 1000 800 600 400 200 0
Fig. 6. Monthly electricity production in GMSWPP.
emissions and air pollution until the end of 1990s. The systematic MSW disposal has been improved in Gaziantep city during the past years. However, the new strategy to construct new plants and to develop the old facility should be planned and taken into consideration using new technology and methodologies due to developing population and rapid increase in amount of MSW. In the city, sanitary landfill has 5.66 MW installed power. This plant produces only 1.25% of total power demand of Gaziantep. The methane that can be produced in Gaziantep from MSW is in the range of 40–52 million m3 and estimated to be as 45–58 million m3 in 2023 [1]. This rate can be improved with some regulations such as: MSW of all districts of Gaziantep should be collected in Gaziantep sanitary landfill for producing more LFG. 1. Alternatively to sanitary landfill, an incineration plant may be installed due to rapidly increasing volume of MSW with respect to population growth. 2. Awareness of public may be raised about MSW segregation due to being very costly process.
Acknowledgments This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) with the project under the Grant number of 114M142. The authors would like to thank TUBITAK and CEV (Clean Energy & Vehicles) Energy.
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Contents lists available at ScienceDirect
Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser
Waste to energy technologies for municipal solid waste management in Gaziantep Alperen Tozlu 1, Emrah Özahi n, Ayşegül Abuşoğlu 2 University of Gaziantep, Faculty of Engineering, Mechanical Engineering Department, 27310 Gaziantep, Turkey
art ic l e i nf o
a b s t r a c t
Article history: Received 2 April 2015 Received in revised form 1 September 2015 Accepted 21 October 2015
Landfill gas (LFG) which is produced by means of municipal solid waste (MSW) treatment activities can be considered as a source of greenhouse gases, including mostly methane. Therefore its management plays an important role. During the process of methane production in MSW plants, LFG is collected, treated and then used for power production purposes. Although there have been many technologies existed, incineration and landfilling methods are mostly preferred all over the world today due to their high energy production potentials. The increasing amount of solid waste arising from municipalities and other sources and its consequent disposal have been the major environmental and economic problems in Turkey. Furthermore, providing more effective and eco-friendly solutions has been a key point for Turkey while being a candidate country for European Union (EU) accession. In this paper, a brief overview on recent technologies and methods applied to MSW management in the world is presented. Current research studies accessed on the literature on MSW are outlined. Moreover, recent MSW management in Gaziantep metropolitan city is displayed with the existing method which produces LFG for power production. Some concluding remarks and recommendations are presented for future developments in MSW management. & 2015 Elsevier Ltd. All rights reserved.
Keywords: Municipal solid waste Landfill gas Waste to energy Gaziantep Power
Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Recent studies on MSW management . . . . . 3. WTE technologies in the world and Turkey . 4. MSW management in Gaziantep . . . . . . . . . 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1. Introduction Municipal Solid Waste (MSW) known as trash or garbage consists of food waste, paper, cardboard, plastics, PET, glass, textiles, metals, wood and leather, nappies, slug, ash, etc. Urbanization level, population growth and technological changes support
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Corresponding author. Tel.: þ 90 342 3601200/2567; fax: þ90 342 3601104. E-mail addresses: [email protected] (A. Tozlu), [email protected] (E. Özahi), [email protected] (A. Abuşoğlu). 1 Tel.: þ90-342-3601200/2524; fax: þ 90-342-3601104. 2 Tel.: þ90-342-3601200/2576; fax: þ90-342-3601104. http://dx.doi.org/10.1016/j.rser.2015.10.097 1364-0321/& 2015 Elsevier Ltd. All rights reserved.
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to increase MSW generation in developing countries. Landfill gas (LFG) which is produced by means of MSW treatment activities can be considered as a source of greenhouse gases, including mostly methane. Thus, all treatment activities of MSW can also be turned into an opportunity for a sustainable production of energy which is known as "waste-to-energy" (WTE). Due to the moisture content of MSW, its lower heating value varies between 5 and 20 MJ/kg. In the same manner, International Energy Agency (IEA) reported that a ton of MSW should have a calorific value between 8 and 12 MJ/kg for an effective energy generation [1]. In previous years, unsanitary landfill activities, open dumping and open incineration methods were common solutions to remove
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MSW from city centers without considering their energy potential and environmental impact. Rapid increase in population and industrial developments has led to findings of new technologies alternatively to these conventional insufficient methods for disposal of MSW. Besides, WTE technologies have become popular research area for governments, researchers and entrepreneurs. There are three fundamental types of WTE technologies [2]: (i) thermal conversion methods (incineration, pyrolysis, and gasification), (ii) biochemical conversion, (iii) landfill. In thermal conversion technology, the mostly used method is incineration. “Incineration” method is mainly the waste destruction in a furnace by controlling combustion at high temperatures. By the incineration method, approximately 70% of total waste mass and thus 90% of total volume can be reduced [3]. Incineration process is completed in three steps which are incineration, energy recovery and air pollution. After incineration process, air pollutants such as SOx, COx, and NOx which are harmful for human health occur. The process is performed between 750 and 1000 °C. “Pyrolysis” is another method in which thermal waste treatment is taken place in an oxygen free environment. There are three types of pyrolysis methods which are conventional pyrolysis (550–900 K), fast pyrolysis (850–1250 K), and flash pyrolysis (1050–1300 K). The third thermal conversion method, “gasification”, is a process that converts MSW into CO2, CO and H2O, which occurs by reacting MSW at high temperatures ( 4700 °C), without combustion, with a controlled amount of oxygen and/or steam [2]. Due to reactor design and operational parameters, gasification process generates other higher hydrocarbons (HC) besides methane. The obtained combustible gas includes CO, CO2, CH4, H2, H2O, some inert gases, trace amounts of higher HCs and various contaminants such as small char particles, tars and ash. The second main group of WTE technology is biochemical conversion. It is much more eco-friendly when compared with others. Biochemical conversion is primarily based on the reaction of microorganism enzymes. Biochemical conversion method is divided into two subgroups as “Anaerobic Digestion” and “Composting” [2]. In “Anaerobic Digestion”, MSW is collected in an oxygen free environment, which is a combination of series of biological processes in which microorganisms break down to biodegradable material. This process which occurs at almost 65 °C decreases the amount of waste and produces biogas for combined heat and power or as a transport fuel. The rest of the production such as inorganic and the inert waste are either incinerated or gasified. By means of this process, 2–4 times as much methane may be produced in 3 weeks when compared with methane production with landfill process in which 6–7 years are needed for 1 t of MSW. On the other hand, “Composting” is a biological decomposition of biodegradable solid waste under predominantly aerobic conditions. It is a natural process of recycling decomposed organic materials into a rich soil known as compost [2]. One of the mostly used and practical technology, a third main group, for WTE today is “Landfilling” which is a soil-based waste disposal technique that uses engineering principles to confine solid waste to smallest area possible and reduce it to the lowest allowable volume in sanitary landfill [4]. Sanitary landfill can be defined as a scientific dumping of MSW using an engineering facility which requires detailed planning and specifications, careful construction and efficient operation [5]. The schematic representation of a typical landfilling process with its steps [3] is shown in Fig. 1. Although landfill is the most common waste treatment techniques in the world, the developed countries prefer to reduce their MSW by using incineration technology due to reduction of approximately 70% of total waste mass and thus 90% of total volume. However, it is a fact that mass burning of MSW creates major environmental problems due to pollutant discharges.
Site Selection
Specific land preparation
Layerwise sanitary land filling
Final soil cover and maturing Compost segregation
Leachate pumping out Combustible gas Water treatment
Final compost Gas engine
Treated water
Electric generator
Fig. 1. Flow diagram of MSW plant based on sanitary landfill [3].
Therefore the best alternative technique for energy recovery for MSW is controlled methane production at landfills. The more details about the advantages and disadvantages of WTE technologies are given in Table 1. In this paper, an overview about WTE technology in the world as well as that in Turkey is presented. Some important current studies on MSW management are outlined. Then, recent MSW management in Gaziantep metropolitan city is displayed with the current WTE technology applied, giving some concluding remarks and recommendations for future developments in MSW management.
2. Recent studies on MSW management Despite of these WTE plants operated for many years, there are still several MSW management problems in the world and the current technology is needed to be developed. For this reason, many investigations are performed to improve the current WTE technologies to increase the amount of generated energy as well as decreasing the amount of MSW. MSW management is crucially important to organize the current WTE plants efficiently and ecofriendly. In this respect, there are also many studies on MSW management for local regions. Many of these studies are related with MSW management and policy of existing systems in local regions presenting the recent portrait and giving further recommendations for developments and/or modifications. Metin et al. [6] presented a general overview of MSW management in Turkey during the last decade. They indicated that the composition of recovered material shows some variations depending on the source (commercial, residential and mixed) and the season of the year, and the majority of the material collected. They clarified that initial investment to set up large-scale collection and recovery schemes still remained to be the major barrier that the municipalities have to overcome.
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Table 1 Advantages and disadvantages of WTE technologies [2]. Technology
Advantages
Disadvantages
Thermal conversion Incineration
– Most suitable for high calorific value waste – Units with high throughput and continuous feed can be set up – Thermal energy for power generation or direct heating – Relatively noiseless and odorless – Low lands are required – Can be located within city limits, reducing transportation costs – Hygienic – Production of fuel gas/oil, which can be used for various – purposes – Control of pollution superior as compared to incineration – Energy recovery with production of high grade soil conditioner – No power requirement for sieving and turning of waste pile – Enclosed system enables trapping the gas produced for use – Controls GHG emissions – Free from bad odor, rodent and fly menace, visible pollution and social resistance – Compact design needs less land area – Net positive environmental gains – Can be done in small scale – Least cost option – Gas produced can be utilized for power generation or direct thermal application – Skilled personnel not required – Natural resources are returned to the soil and recycled – Can convert marshy lands to useful areas
– Least suited for aqueous, high moisture content, low calorific value and chlorinated waste – Toxic metal concentration in ash, particulate emissions, SOx,NOx, chlorinated compounds, ranging from HCL to dioxins – High capital and O&M costs – Skilled personnel required – Overall efficiency for small power stations is low
Pyrolysis/ gasification
Biochemical Conversion
Landfilling
Magrinho et al. [7] introduced the basic principles of MSW management in Portugal. They stated that it was needed to give a considerable amount of effort in order to obtain real and significant positive evolution in MSW prevention, reduction and recovery. Turan et al. [8] showed a brief history of the legislative trends in Turkey for MSW management. They claimed that primitive disposal methods such as open dumping and discharge into surface water had been used in various parts of Turkey although strict regulations on MSW management were in place. They also clarified that 70.57% of the total amount of MSW was disposed of without any control. Manaf et al. [9] studied on MSW management in Malaysia. They emphasized that a new institutional and legislation framework has been structured with the objectives to establish a holistic, integrated, and cost-effective MSW management system, with an emphasis on environmental protection and public health, increasing the efficiency of MSW management towards 2020. Aydoğan et al. [10] determined and explained the MSW management, solid waste quality, collecting method of solid wastes, transportation and waste disposal options in Gaziantep. Oteng-Ababio et al. [11] studied on a case study in new MSW technologies in Accra city in Africa. They stated that rigorous evaluation of all waste management options was the best way to safeguard against ill-fated investments and toward meaningful advancement in sound MSW management in the long-term. Herva et al. [12] presented the results of the environmental evaluation of MSW processes in Portugal in the period 2007–2011. They concluded that the environmental gains of MSW were higher than the environmental impacts, and highlighted that the electricity generated in the energy recovery plant was remarkable. On contrary to all these, Fobil et al. [13] discussed research experiences in Accra, Ghana for utilizing MSW for energy generation. They concluded that MSW had a low energy recovery efficiency,
– Net energy recovery may suffer in waste with excessive moisture – High viscosity of pyrolysis oil may be problematic for its burning and transportation
– Unsuitable for wastes containing less organic matter – Requires waste segregation for improving digestion efficiency
– – – – – –
Surface runoff during rainfall causes pollution Soil and groundwater may get polluted by the leachate Yields only 30%–40% of the total gas generated Large land area required Significant transportation costs Cost of pre-treatment to upgrade the gas to pipeline quality and leachate treatment may be significant – Spontaneous explosion due to methane gas build up
approximated at 40% recovery, due to high equipment installation and plant maintenance costs. Leachate is an important problem in a sanitary landfill area such that leachate water may diffuse into underground water. Hence it is very crucial for public health and this problem have to be overcome. Ağdağ [14] presented a general overview and compared old and new MSW management practices in Denizli. It was claimed that there were still some deficiencies in the new MSW management system such as no leachate treatment and poor source separation collection. The content of MSW also plays an important role in MSW management and for efficiency of energy production. In this respect, many studies can be found in selection, sorting and segregation processes of MSW. Horttanainen et al. [15] collected Finnish studies concerning the composition and energy content of mixed MSW (organic waste, paper, plastic and cardboard, etc.), which is incinerated for energy production. They found that in mixed MSW, the renewable share of the energy content could be significantly lower than the general assumptions (50–60%). They also claimed that the low share of biowaste in mixed MSW decreases the moisture content of the waste, increasing the heating value. Besides of this, it was also found that high share of plastic increases the heating value and the nonrenewable share of energy in the waste material. Also the improvement of paper and cardboard recycling is seen to decrease the share of renewable energy in mixed MSW. The available WTE techniques are compared by many scientists regarding the waste material, capacity of landfill area, etc. OjedaBenitez and Beraud-Lozano [16] performed an analysis for sanitary landfill and the uncontrolled dump in four cities of Mexico. They pointed out the disadvantage of uncontrolled dump due to pollutants and a serious threat to human health, and proposed a development
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and an extensive construction of integrated sanitary landfills. Bovea et al. [17] performed a case study on environmental assessment of alternative MSW management strategies in Spain applying LCA methodology. They found that biogasification and energy recovery achieved better environmental performances than landfill without energy recovery. Cheng and Hu [18] presented a perspective on MSW discussing the major challenges in expanding WTE incineration in China in terms of capital and operational costs, equipment corrosion, air pollutant emissions and fly ash disposal. They claimed that WTE incineration gave greater contribution for supplying renewable energy in China. Kanat [19] presented the situation of MSW management in İstanbul considering current requirements and challenges in relation to the optimization of İstanbul's MSW collection. It was stated that there was a great need to reduce the volume of solid waste in Istanbul and recommended to design a waste-management system according to capacity. It was mentioned that landfilling technique was not a proper solution for metropolitan cities, such as İstanbul. The WTE techniques are also considered in terms of their emissions. Lino and Ismail [20] studied on the energy savings and the avoided emissions of CO2 to the atmosphere as a result of recycling and production of LFG from landfills in Brazil. It was mentioned that the solid waste deposited in landfills without treatment impacted on the public health. And they also stated that the anaerobic degradation of the organic matter to produce LFG alleviated the ambient from the CO2 and CH4 emissions otherwise liberated to the atmosphere. Udomsri et al. [21] presented an evaluation of the potential of MSW incineration for climate change mitigation and promotion of biomass-based electricity production in a more sustainable direction in Thailand. They resulted that MSW incineration had the ability to lessen environmental impact associated with waste disposal, and it could contribute positively towards expanding biomass-based energy production. It was emphasized that hybrid cycles could be used to improve system performance and overall electrical efficiency of conventional incineration. Akinci et al. [22] performed a future planning for the waste management in Izmir, Kula, and Usak. They proposed methane production in Izmir for the biological degradation of Izmir green wastes, and composting method for Kula and Uşak. Arafat et al. [23] studied on the environmental impacts for MSW treatment processes with energy recovery potential using life cycle assessment (LCA) methodology. They claimed that it was the best to recycle paper, wood and plastics; to anaerobically digest food and yard wastes; and to incinerate textile waste. In view of the treatment processes, anaerobic digestion and gasification were found to perform better environmentally than the other processes, while composting had the least environmental benefit. Melikoğlu [1] estimated the potential of electricity generation via MSW combustion and methane harnessing at the landfills of 81 Turkish cities. It was claimed that the energy recovery from MSW is less than 1% countrywide. Melikoğlu [1] preferred incineration technique for further methods for energy production from MSW. Phillips and Mondal [24] performed a mathematical model of sustainability of options for MSW disposal in India. They clarified that gasification may be the best potential sustainable option for MSW disposal due to positive impacts overall for the local environment and community. Hossain et al. [25] reviewed the types of MSW in Bangladesh. They stated that WTE incineration was playing a fundamental role for renewable energy production reducing space for new landfills. However, low calorific value and high water content were pointed out to deficit the power generation from MSW incineration.
3. WTE technologies in the world and Turkey It can be stated that there are many WTE plants which have been constructed in the world since 1990's. In 1990, 394 trillion Btu of energy which was produced from MSW was consumed in
USA. On the other hand, some of energy demand in Japan was provided from 102 waste incineration plants in the end of 1991. Also there were many WTE plants in Germany in the 90's. In United Kingdom, the 70th report by the Royal Commissions on Environmental Pollution emphasized the importance of modern technology in MSW plants [2,26]. Agricultural biomass is used to generate electricity in Poland. At the end of 2012, there are 29 agricultural biogas plants in Poland with an average installed capacity of 1 MW [2,27]. Agricultural biomass has also been used in many African countries including Ghana to produce decentralized rural energy. The total output is around 12.5 kW electric power using two generators rated 5 kV A and 7.5 kV A. The produced electricity is supplied to the community using a local grid of 230 V for 12 h per day [2,28]. In Southeastern Asia, Malaysia has also been very active in MSW techniques. Methane emissions from Malaysian landfills for 2010 were equivalent to 2.20 109 kW h of electricity [2,29,30]. In Europe, Italy has many anaerobic co-digestion plants ranging between 50 kW and 1 MW [2,31]. Thessaloniki in Greece has been following the integrated solid waste management and energy production, and now biocell technology is used in order to utilize the better biogas production using innovations [2,32]. Also, in Singapore, food waste is used as an alternative option for the energy recovery and many policies are developed for MSW technology and management [2,33]. Canada has also accelerated the MSW technology to convert MSW to energy by means of designed various systems to recover the energy of MSW. They produce 134.6 MW h per year of surplus energy [2,34]. Although the historical background of WTE technology dates back to 1990's in the world and the most of energy needed in Turkey has been imported, the efficient technology in MSW management could not be achieved in Turkey until 2002. The developments in WTE technology have been accelerated in Turkey over the last two decades by means of the government's recent progress in the frame of Turkey's 2023 vision. 30% of the demand of electricity in Turkey is planned to be met from renewable energy sources by 2023. The increasing amount of solid waste arising from municipalities and other sources and its consequent disposal have been the major environmental and economic problems in Turkey. These problems enforce MSW to be one of the renewable energy sources in Turkey such that 25 million tons of MSW is produced annually nationwide. Landfilling technique which is used to generate energy from MSW is a primary waste management option in Turkey. However, this technique has some environmental problems such as anthropogenic methane and carbon dioxide emissions, water pollution due to leachate production, etc. According to the European Union (EU) landfill directive (1999/31/EC), the amount of biodegradable organic waste deposited in landfills should be decreased by 65% of the 1995 level by 2016. On contrary to this, landfill technique is more eco-friendly one when compared with incineration technique [1]. Most of people which are about 83% of the population in Turkey receive MSW services, as well as this value is about 99% in municipality area, but still there are more than 2000 open dumps in Turkey [8,35]. According to Turkish Statistical Institutes database, 176,300 GW h of electricity was produced in 2006 but only 0.2% of the produced energy was provided from renewable energy sources and waste [35] whereas the consumption of electricity was about 143,070 GW h in 2006. In 2013, there was a significant increase in energy production from renewable energy sources and waste such that 4.2% of 240,154 GW h electricity was produced from the mentioned sources whereas the total electricity consumption was 194,923 GW h. According to 2013 values, there were 80 sanitary landfills, 2 incineration plants and 5 compost plants in Turkey. The number
A. Tozlu et al. / Renewable and Sustainable Energy Reviews 54 (2016) 809–815
of sanitary landfills in Turkey is planned to increase 130 at the end of 2017. The WTE techniques applied in Turkey by 2012 is summarized in Fig. 2. According to Turkish Statistical Institute values [35], 59.9% of MSW was disposed in municipality sanitary landfills, 0.11% of MSW was combusted with incineration, 1.15% of MSW was disposed by using a recycling method, and 37.8% of MSW was accumulated by means of municipality dumps in Turkey by 2012. The rest of waste (0.64% of MSW) was disposed with other methods. The situation of MSW management in Turkey with comparisons of other regions is tabulated in Table 2 [35,36]. As can be seen from Table 2, sanitary landfill for disposal of MSW is more preferable technique in Turkey. Besides, less popular technique in Turkey is seen to be incineration one as can be noticed from the table. Although incineration technique in Europe is a common method, it is not favorable in North America. In North and Latin America, sanitary landfill is mostly used technique. On the other hand, open dump disposal method is very common in Asian and African countries.
4. MSW management in Gaziantep Gaziantep, which is located in the southeast region of Turkey, is the 6th biggest city as a population which is about 2,000,000. Total land area of Gaziantep is 7642 km2. With the total consumption of electricity, Gaziantep is on the 11th rank in Turkey [35]. Annual electricity consumption per capita is 2560 kW h in Gaziantep. The reason of this high electricity consumption is clearly due to dense population and industrial facilities in the city. Over the last decades, industry in Gaziantep has developed very rapidly, especially in plastic, textile, food, carpet and package industries. In Gaziantep, there are some private companies which produce their own electricity using natural gas, fuel oil, LFG and also hydropower. The installed power capacities of these companies are shown in Fig. 3 [37]. Among this distribution, LFG produced from MSW plays an important role for energy production in Gaziantep, in terms of WTE concept. As the historical background of MSW management in Gaziantep is considered, MSW was collected by Gaziantep
813
Metropolitan Municipality in an unsanitary landfill until 1996, for only disposal purpose at Beylerbeyi location which was too close to the city center. After 1993, Gaziantep Metropolitan Municipality has started to construct a sanitary landfill plant with an installed power capacity of 5.66 MW for both disposal of MSW and energy production from produced LFG in Mazmahor, Uzundere under the grant of Southeastern Anatolia Project (GAP). This constructed sanitary landfill has 32.3 ha solid waste storage area and also 10,000,000 m3 solid waste capacities which will fulfill the need until 2046 [10]. This plant produces 1.25% of total power demand of Gaziantep. Average percentage compositions of MSW in Gaziantep and its comparison with other metropolitan cities is given in Table 3 [6,10,14]. Fig. 4 shows the schematic representation of Gaziantep Municipal Solid Waste Power Plant (GMSWPP). In GMSWPP, LFG is created during the anaerobic decomposition of organic substances in domestic solid waste, industrial, and medical wastes. The total MSW carried to GMSWPP is 1500 t daily. All wastes collected in GMSWPP are subjected to mechanical segregation of plastic, metal and glass, and then rest of MSW is sent to sanitary landfilling area. On the other hand, medical waste is sterilized first as a pretreatment and then sent into landfilling area. MSW which is buried underground in landfilling area is led to produce LFG for months. The produced LFG from the storage area is collected from 114 high density polyethylene (HDPE) funnels with a diameter of 800 mm, which are underground in 8–41 m depths. The collected LFG is then transferred to 6 manifold stations. If temperature of LFG is higher than 40–45 °C, it is cooled through a heat
8.6 9.73 20
8 6.7
5.66
24.63
189
21 25
37
Sanitary Landfill
49
Incineration Recycling Open Dump Open Burning
49
Karkam1ş Dam and HEPP (HE)
Goren 2 TPP (NG)
Goren 1 NGPP (NG)
Gülsan Syn. Man. NGPP (NG)
Başp1nar CU (FUELOIL)
Naksan EPP 2 (NG)
Naksan CU (NG)
Melike Tex. NGPP (NG)
Selçuk Tex. NGPP (NG)
Naksan EPP (NG)
Gürteks Tex. NGPP (NG)
Gaziantep MSW Plant (LFG)
Other HEPP: Hydroelectric Power Plant, TPP: Thermal Power Plant NGPP: Natural Gas Power Plant, CU: Cogeneration Unit EPP: Energy Power Plant, SEPP: Solar Energy Power Plant
Other Fig. 2. Distribution of WTE techniques applied in Turkey.
Fig. 3. Distribution of energy production in MWe in Gaziantep.
Table 2 Worldwide MSW management in 2012 [35,36]. Region
Sanitary landfill (%)
Incineration (%)
Recycling (%)
Open dump (%)
Open burning
Other (%)
Turkey Africa Asia Europe North America Latin America
59.9 29 31 27 91 59
0.11 2 5 14 0 2
1.15 4 8 11 8 3
37.8 47 51 33 0 31
0.4 9 2 12 0 4
0.64 9 3 3 1 1
A. Tozlu et al. / Renewable and Sustainable Energy Reviews 54 (2016) 809–815
exchanger by means of chilled water in the direction which is denoted with blue arrows in Fig. 4. LFG which is under 40–45 °C is sucked into tandem demisters/filters in order to eliminate water and particulates such as aluminum, ash, etc by using blowers having the operating vacuum pressure of 6 kPa. There is one flare stack mounted at the exit of blowers in order to drain excess LFG at any emergency case. The collected water is sent back to a drain tank. The filtered LFG sucked through four pipelines is collected in A/C tanks for desulphurization process. At the exit of the A/C tanks, if the operating pressure exceeds 14.5 kPa gage, excess LFG is sent back to the beginning of process pipeline by using a pressure control valve. At the same time, volumetric content of LFG are measured and also recorded on a control panel. At any instant, the average volumetric values of the components of LFG are given in Table 4. The percentage of methane in LFG according to the monthly distribution in 2014 is also shown in Fig. 5. As can be seen from the figure, the average volumetric percentage of methane is nearly 45. Moreover, the operation is stopped automatically when methane content is decreased below 38% and oxygen is increased above 6%. The flow rate, operating pressure and temperature data are measured at 7, 15 and 5 stations, respectively throughout the process pipeline. The volumetric flow rate of LFG is measured 17.5 m3/min through the main pipeline. After the reduction of H2S content in LFG to 100–120 ppm, it is then pumped into three 1.13 MW Janbacher-4 type gas engines coupled with generators to produce electricity. The exhaust gas is recorded as nearly 550–600 °C at the end of the process. Due to the increasing amount of MSW in Gaziantep, two 1.13 MW Janbacher-4 type gas engines will be
constructed to the existing system in order to increase the capacity of the power plant. Fig. 6 illustrates the monthly energy production in MW h in the power plant. The average energy production for each month is almost 1650 MW h which satisfies the energy demand of 2000 households in Gaziantep.
5. Conclusions In Gaziantep, there was only one unsanitary landfill which had serious environmental problems because of uncontrolled gas Table 4 Average volumetric composition of LFG produced in GMSWPP. Components
Chemical formula
(%) Dry volume
Methane Carbon dioxide Carbon monoxide Nitrogen Oxygen Hydrogen Hydrogen Sulfur
CH4 CO2 CO N2 O2 H2 H2S
45–53 30–32 1–5 2–6 3–5 3–7 0–2
CH4 60 50 40
Table 3 Composition of MSWc in 6 metropolitan cities in Turkey [6,10,14].
% 30
Cities
Organic
Paper/cardboard
Plastic
Metal
Glass
Others
Istanbul Izmir Bursa Gaziantep Adana Mersin
43 46 53.1 41.6 64.4 63
7.8 12 18.4 6.1 14.8 18.4
14.2 12 11.6 4.8 5.9 6.7
5.8 3 3 1 1.4 1.3
6.2 4 3.4 7.1 3.1 3.1
23.1 23 10.5 39.5 11.4 7.6
20 10 0
N FE B M A R A PR M A Y JU N JU L A U G SE P O CT N O V D EC
(%) Compositions
JA
814
Fig. 5. Monthly methane content in LFG produced in GMSWPP.
Fig. 4. Schematic layout of GMSWPP.
A. Tozlu et al. / Renewable and Sustainable Energy Reviews 54 (2016) 809–815
JA
N FE B M A R A PR M A Y JU N JU L A U G SE P O CT N O V D EC
MWh
ENERGY PRODUCTION 2000 1800 1600 1400 1200 1000 800 600 400 200 0
Fig. 6. Monthly electricity production in GMSWPP.
emissions and air pollution until the end of 1990s. The systematic MSW disposal has been improved in Gaziantep city during the past years. However, the new strategy to construct new plants and to develop the old facility should be planned and taken into consideration using new technology and methodologies due to developing population and rapid increase in amount of MSW. In the city, sanitary landfill has 5.66 MW installed power. This plant produces only 1.25% of total power demand of Gaziantep. The methane that can be produced in Gaziantep from MSW is in the range of 40–52 million m3 and estimated to be as 45–58 million m3 in 2023 [1]. This rate can be improved with some regulations such as: MSW of all districts of Gaziantep should be collected in Gaziantep sanitary landfill for producing more LFG. 1. Alternatively to sanitary landfill, an incineration plant may be installed due to rapidly increasing volume of MSW with respect to population growth. 2. Awareness of public may be raised about MSW segregation due to being very costly process.
Acknowledgments This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) with the project under the Grant number of 114M142. The authors would like to thank TUBITAK and CEV (Clean Energy & Vehicles) Energy.
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