Assessment of environmental and economic performance of Waste-to-Energy facilities in Thai cities

Renewable Energy 86 (2016) 576e584

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Assessment of environmental and economic performance of Waste-to-Energy facilities in Thai cities S.N.M. Menikpura*, Janya Sang-Arun, Magnus Bengtsson Sustainable Consumption and Production (SCP) Group, Institute for Global Environmental Strategies (IGES), 2108-11 Kamiyamaguchi, Hayama, Kanagawa 240-0115, Japan

a r t i c l e i n f o

a b s t r a c t

Article history: Received 26 March 2014 Received in revised form 25 July 2015 Accepted 24 August 2015 Available online xxx

Waste-to-Energy (WtE) technologies seem to be an option to tackle the growing waste management problems in developing Asia. This paper presents a quantitative assessment of the environmental and economic attributes of two major WtE technologies: landfill gas to energy (LFG-to-energy) and incineration in Thai cities. Net greenhouse gas (GHG) emissions, net fossil resource consumption and net lifecycle cost (LCC) were used as the basic indicators for measuring performance of these two technologies from a life cycle perspective. The assessment found that at the current efficiency level, both the LFG-toenergy project and the incineration facility contribute to GHG mitigation and fossil resource savings as compared to the Business as Usual (BAU) practice. However, the financial returns from these operations are very low and insufficient to compensate the costs. The paper argues that substantial improvements of WtE plants can be made by adopting proper management practices, enhancing the efficiencies of energy production. Such upgrading would further reduce GHG emissions, increase fossil resource savings and strengthen the financial performance to the benefit of local governments. The authors recognize the potential of incorporating other treatment options along with WtE technologies, for moving towards more sustainable waste management approaches like integrated waste management systems. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Municipal Solid Waste (MSW) Waste-to-Energy (WtE) Life Cycle Assessment (LCA) Asia Thailand

1. Introduction Rapidly growing populations have accelerated the generation rate of Municipal Solid Waste (MSW) in cities, causing this issue to become more and more crucial both for the daily management and long term sustainability of cities. The urbanisation of the world's population is set to continue: by 2025 the world's population is projected to be about 8 billion, of which nearly 5 billion will live in urban areas. By 2015, there will be 33 mega-cities in the world, and 27 of them will be located in the developing world especially in South-East-Asia [1,2]. At present, MSW generation in Asia surpasses 1 million tonnes/day, and it is estimated that in 2025, this figure will increase to 1.8 million tonnes/day [3]. Most of the cities in developing Asia are practicing open dumping and partly controlled landfilling without gas recovery. These simple disposal methods have well-documented adverse impacts on climate change, human health and the environment and

* Corresponding author. E-mail addresses: (S.N.M. Menikpura).

[email protected],

http://dx.doi.org/10.1016/j.renene.2015.08.054 0960-1481/© 2015 Elsevier Ltd. All rights reserved.

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there is general agreement that improvements are needed [4,5]. In addition, space for landfill construction is limited in and around cities. Waste therefore often has to be transported long distances out of the urban area which requires additional resources and increases operation costs [6]. Climate change is a global issue of increasing importance and urgency, thus leading cities in developing Asia need to plan climate-abating waste management plans [7]. Energy recovery from waste could be an option for greenhouse gas (GHG) mitigation as this energy would meet some of the increasing energy demands in cities while minimising long-distance waste hauling that consumes a great deal of energy. Therefore, it would appear that developing cities in Asia are strong candidates for refining renewable energy from waste streams as this would contribute to gradually replacing traditional petroleum refineries [8]. There is a fastgrowing trend in Asia to move towards properly designed and managed sanitary landfills with gas recovery systems since such projects both provide an opportunity to generate renewable energy and opportunities to receive financial support through carbon financing [9]. In addition, some developing Asian cities are interested in waste incineration, which reduces waste mass by 75% and volume by up to 90%, as a solution to the acute lack of landfill sites.

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The prospects of improving sanitary conditions combined with the expected financial benefits from energy recovery add further to this interest [10,11]. Incineration would directly eliminate methane emissions from anaerobic degradation of waste at landfill sites and could also displace some fossil fuel-based electricity generation. Due to all these reasons, there is growing interest in the application of these technologies as a near-term solution to the growing waste management challenges in developing Asia. In general, the application of WtE technologies which are welldesigned to suit the local situation would contribute to GHG mitigation, energy recovery and reducing health risks. Efficiency of energy recovery would strongly effect the significance of achieving the environmental and economic co-benefits [12]. However, inefficiencies are a common obstacle in most of the cases of failure in developing Asia [9,13]. For instance, there is a high possibility of failure if these technologies are implemented in developing countries without proper adaptation to local conditions since these are designed mostly for the situation in developed countries. Further, these technologies are relatively expensive treatment options in waste management due to high capital investment and high operating and maintenance costs. Therefore, the design phase of any kind of WtE project is very important for careful selection and adaptation of technologies which best suit the local conditions. This study assessed the environmental and economic performance (GHG emissions, fossil energy consumption/savings and financial returns to local entities) of two WtE technologies based on data from currently operating facilities in Thailand. Further, possible improvements have been suggested for enhancing the efficiency of WtE technologies for improving environmental and economic benefits. The research findings would be beneficial to all levels of stakeholders in waste management for understanding the common issues of WtE technologies in developing Asia and also for identifying opportunities for strengthening the financial returns and environmental benefits. It should be noted that the toxicological effects of pollutants emitted from incineration has been the subject of much debate in many countries. Therefore, such toxicological effects and the potential for implementing efficient pollution control devices should be a topic for future studies. 2. Methodology The evaluation of existing WtE technologies from an environmental and economic perspective via a life cycle approach is an important step for upgrading the existing technologies as well as for making sound decisions at the design phase of the new systems. This study was done to evaluate the environmental and economic attributes of two major WtE technologies in Thailand. Rachatewa landfill, located in the Bangkok Metropolitan Area (BMA), was evaluated to understand the common environmental and economic attributes of sanitary landfill with a gas recovery system in cities. There is no functioning incineration plant in BMA and, therefore, the Phuket plant (the biggest incineration plant in Thailand) was assessed in order to understand the common pros and cons of this technology in the Asian context. 2.1. Selection of the study locations and description of the existing WtE systems 2.1.1. Sanitary landfill with gas recovery in BMA Bangkok is one of the megacities in developing Asia which is faced with the urgency of taking the right action and adopting the right technology for tackling the growing waste management problem. In Thailand, more than 20% of MSW is generated in BMA [14]. In the year 2011, the waste generated in BMA amounted to 8700 tonnes/day. The Jaroensompong Corporation initiated a

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landfill gas recovery project at the Rachathewa sanitary landfill site in BMA, which is the first CDM project to utilise LFG for electricity generation on a commercial basis in Thailand [15]. The Rachathewa sanitary landfill site was constructed in 1999. The total area of the landfill site (site I and site II) is 40 ha and the height of the landfill is 18 m. The existing LFG recovery project was initiated using site I which is 8 ha in size. The total amount of accumulated waste was 4.7 million tonnes, consisting of 2.5 million tonnes of newly disposed waste and 2.2 million tonnes of old waste moved from the former neighbouring landfill site when that site was shut down in 2001. During the active phase of the Rachathewa sanitary landfill site (1999e2001), the MSW disposal rate was 3500 tonnes/day. The average composition of the disposed MSW consisted of food waste (40.89%), yard waste (14.20%), plastics (25.03%), paper (15.58%), glass (1.82%), metal (0.21%) rubber and leather (0.68%), and other waste (0.65%) [16,17]. This landfill has been designed to maintain sanitary conditions. This includes a composite liner system, leachate collection and treatment system and an LFG recovery system. Recovered LFG is utilised as a fuel source for running a 1 MW generator to produce electricity with 45.5% efficiency. The excess amount of extracted LFG is flared. The LFG recovery and crediting period has been limited to 10 years with the project commencing in 2008 and intended to continue until 2017. The electricity production capacity has been limited to 31.3 kWh per tonne of waste disposed. 10% of the electricity produced is utilised for operational activities at the landfill site and the remaining 90% is sold to the grid. 2.1.2. Incineration plant in Phuket Most of the cities in Asia have strong interest in the application of waste incineration as a solution to the problem of reducing the volume of waste. This is because there is insufficient land area available to dispose of waste and also this could contribute to generating renewable energy in the city. The biggest existing incineration plant in Thailand is located on Phuket Island. The designed capacity of the existing incineration plant is 2.5 MW and this plant was installed in 1999. The expected life time of this incineration plant is 20 years and it manages more than 50% of the waste generated in Phuket. At the moment, 300 tonnes of collected waste is sent to the incineration plant. Similar to most of the developing Asian cities, waste separation is not practiced in Phuket and mix waste is being used at the incineration plant. The average composition of waste combusted in the Phuket incineration plant consists of food waste (23.5%), yard waste (11.2%), plastics (19.0%), paper (25.7%), rubber and leather (5.0%), textile (2.1%) and incombustibles (13.6%). The received waste has very high moisture content and it is stored in a waste pit for 4e5 days in order to remove the moisture. Within this period 50 tonnes of moisture is drained from the moist waste, and the remaining 250 tonnes of waste is used for the incineration process. The moisture content of the combusted waste is 40e42%. The high moisture content of the mixed waste has an influence on reducing the efficiency of the incineration plant and the electricity generation capacity. The average electricity production potential in the Phuket incineration plant amounts to 144 kWh per tonne of combusted waste (which is equal to 120 kWh/tonne of collected waste, see Fig. 1). Plant operation activities require 60% of the electricity produced with the remaining 57.6 kWh/tonne of combusted waste (48 kWh/tonne of collected waste) being sold to the grid. Residue waste (200 kg per tonne of waste) from incineration (ash and non-combustibles) is being disposed in a sanitary landfill next to the incineration facility. Several techniques has been employed for pollution control. Calcium hydroxide or lime is used to absorb the SO2 and HCl. Temperature is maintained 800e1000
C to control the formation of NOx and dioxine. Furthermore, activated

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Fig. 1. LCA framework designed to assess the environmental and economic impacts of selected WtE technologies (per tonne of collected waste).

carbon is also used to avoid the dioxin emissions.

2.2. Approach for evaluating environmental and economic implications In recent years, the Life Cycle Assessment (LCA) approach has been identified as a tool for an holistic assessment of MSW management [18,19]. The application of an LCA is very useful, particularly for assessing the environmental and economic impacts associated with an MSW management system, as it enables the identification of issues of concern and possible policies for mitigating more effectively the direct and indirect impacts [5]. As the initial step of this assessment, the life cycle phases of the LFG to energy recovery project in BMA and the incineration in Phuket were identified, see Fig. 1. Interviews were conducted with personnel in top management positions in order to find site specific data on both of the WtE technologies. Data was gathered with respect to waste collection and transportation, input material, energy consumption for operational activates (e.g. diesel consumption, electricity requirement) and recovery of energy. In order to understand the benefits of energy recovery, credits were provided for the avoided environmental and economic burdens from the potential displacement of the equivalent amount of conventional energy. The functional unit was defined as “one tonne of collected MSW management” under the existing situation for the selected WtE technologies. Usually, the electricity production capacity from incineration plants is expressed per tonne of combusted waste. However, in this analysis, electricity production is accounted for on the basis of per tonne of collected waste in order to align with the functional unit. It should be noted that the results of these two technologies cannot be compared since the basic variables, such as logistical arrangement and waste composition, are different in the two systems.

2.3. Selection of indicators for the assessment GHG emissions and their influence on climate change and the depletion of fossil fuels are considered to be critical global environmental challenges. GHG emission from MSW management is recognised as an important environmental burden resulting from waste degradation at disposal sites and the combustion of waste. In addition, existing systems use a considerable amount of fossil energy for operational activities which leads to depletion of fossil resources. However, by recovering energy using the above WtE technologies, there is the possibility of contributing to both GHG reductions and fossil resource savings. Therefore, to assess the severity of those crucial impacts, “net GHG emission” and “net fossil resource consumption” are considered as the most relevant environmental indicators in this study. One very important decisive factor in the sustainability of WtE technologies is whether they are economically viable. A detailed financial analysis via a Life Cycle Cost (LCC) assessment would be an appropriate approach for making decisions on cost effectiveness and economic sustainability within a common LCA framework [5,20]. Hence, LCC was selected as the economic indicator to perform the evaluation. However, environmental cost (monetary value for the environmental emissions) was not accounted for in LCC since there is no existing methodology to account for the environmental cost in the Thai context.

2.3.1. Environmental performance: quantification of net GHG emissions The major GHG emissions from existing WtE technologies are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). For instance, CO2 emissions resulting from combustion, during the incineration of waste containing fossil origin items such as plastics, certain textiles, rubber, liquid solvents, would be significant. Also, there is the possibility of CH4 and N2O like GHG emissions during

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the combustion process [21]. In addition, CO2, CH4 and N2O can be emitted from incineration due to fossil fuel and grid electricity consumption for transportation and operational activities. As far as the LFG-to-energy recovery project is concerned, part of generated CH4 can escape into the atmosphere due to the inefficiencies of the collection system. Similar to incineration, CO2, CH4 and N2O can be emitted from fossil fuel and grid electricity consumption for transportation and operational activities. Following the IPCC (2006) guidelines, GHG emission potential from the two WtE technologies was quantified taking into consideration all the phases of the life cycle in a systematic way. The impacts of GHGs are considered in terms of global warming over a 100 year timeframe and expressed in units of CO2 equivalent. Net GHG emissions from WtE technologies can be estimated as follows:

GHGGross ¼

X X X ðQi T  EFi Þ þ ðQi O  EFi Þ þ ðQi TP  EFi Þ i

GHGNet

i

where Qi e Magnitude of ith GHG from T e Transportation, O e Operation, TP e Treatment Process (e.g. fossil based CO2 emissions from incineration, fugitive CH4 emission from landfilling), PA e Potential Avoidance via energy recovery, EFi e Equivalency Factor of ith GHG. 2.3.2. Environmental performance: quantification of net energy consumption Each and every stage of waste management consumes a significant amount of non-renewable energy or fossil fuel for operational activities. However, it may be possible to reduce fossil fuel depletion using recovered energy from WtE plants, with consequent avoided use of virgin fossil resources. In this study, total fossil fuel consumption for waste management (e.g diesel fuel for transportation, natural gas, coal and fuel oil for grid electricity production) was measured as crude oil equivalents. For fossil fuel consumption, the characterisation factors are derived relative to the energy content “oil, crude, feedstock, 42 MJ/kg, in ground” [22].

X X X ðQi T  EFi Þ þ ðQi O  EFi Þ þ ðQi TP  EFi Þ

FRNet ¼ FRGross 

i

LCCGross ¼ CE þ OMC LCCNet ¼ LCCGross  LCR LCR ¼ Service fee from the household þ Revenues from selling electricity þ CDM credits where, CE e Capital Expenditure, OMC e Operational & Maintenance Cost, LCR e Life Cycle Revenue. 2.4. Measurement of the ultimate environmental-economic progress

i

i

Thailand context. In order to make the final decision on the economic feasibility of WtE technologies, life cycle revenues (e.g. sale of electricity, service fee from households) should also be included to estimate the net LCC. Gross and net LCC can be quantified in terms of a country's currency per tonne of waste management. Gross and net LCC is estimated as follows:

i

X ¼ GHGGross  ðQi PA  EFi Þ

FRGross ¼

579

i

X ðQi PA  EFi Þ i

where FRGross e Total Fossil Resource consumption, Qi e Magnitude of ith fossil resource utilised for T e Transportation, O e Operation, TP e Treatment Process, PA e Potential Avoidance via energy recovery, EFi e Equivalency Factor of ith fossil resource relative to “oil, crude, feedstock, 42 MJ/kg, in ground”. 2.3.3. Economic performance: quantification of net LCC For the net LCC assessment, all cost elements should be identified in a systematic way. Total capital expenditure and total operation and maintenance costs (costs involved in waste collection and transportation, labour costs, and the costs involved in utilities, operating suppliers, insurance, taxes, etc.) must be incorporated in the LCC analysis. WtE technologies have also given rise to negative environmental effects and those externalities should be accounted for in LCC estimations since it reflects the environmental damage in monetary terms. However, in this study, the environmental cost (monetary value for the environmental emissions) is not included since there is no reliable model to calculate the externalities in the

In order to determine the effectiveness of WtE projects, the net impact was always compared with the “business as usual (BAU)” practice. Sanitary landfilling without gas recovery sysem was considered as BAU scenario for the study locations which is the common treatment option in most of the Thai cities. The GHG emissions potential from BAU was estimated taking into account the characteristics of the waste concerned and the average landfill conditions of the study locations. 3. Results and discussion 3.1. Estimation of environmental performance: net GHG emissions 3.1.1. Net GHG emissions from the LFG to energy recovery project in BMA The GHG emissions were estimated taking into account all the phases of the life cycle. GHG emissions from waste transportation in BMA using compactor trucks amounted to 26 kg CO2-eq per tonne of waste. Further, GHG emissions potential from operational activities (diesel fuel consumed for spreading, compaction and covering waste using heavy machinery) amounted to 10 kg CO2-eq per tonne of waste. The highest share of GHG emissions resulted from anaerobic degradation of waste in the landfill. The estimated CH4 generation potential from 1 tonne of waste is 64.65 kg which corresponds to 1360 kg CO2-eq. Taking into account GHG emissions from all phases, such as transportation and operational activities at the landfill and waste degradation, the estimated gross GHG emissions from the sanitary landfill at Rachathewa is 1396 kg of CO2-eq/tonne of waste, see Fig. 2.

Fig. 2. GHG emissions from the LFG-to-energy recovery project and comparison with BAU (sanitary landfill without gas recovery) practice.

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As a result of establishing the existing LFG to energy recovery project, a part of generated CH4 is captured (8.11 kg CH4/tonne of waste disposed) to produce electricity. In addition, the electricity produced from recovered LFG is used to replace conventional electricity production (fossil fuel based) and the associated GHG emissions can be avoided (GHG emission from Thai grid electricity production 560 kg CO2-eq/MWh). Thus, the total GHG avoidance potential from the LFG-to-energy project is 186 kg CO2-eq/tonne of waste disposed. The net LCC was calculated by subtracting the above revenues from the gross LCC. As shown in Fig. 2, the net GHG emissions potential from the existing LFG-to-energy project in BMA amounts to 1210 kg CO2-eq/tonne of waste disposed, see Fig. 2. In order to understand the effectiveness of such LFG-to-energy recovery projects on GHG mitigation, the net impact of the project waste was compared with the net impact of sanitary landfill without gas recovery, which is the BAU practice in most of Thai cities. If the waste generated in BMA is disposed of in a sanitary landfill (without gas recovery), life cycle GHG emissions would be equal to 1396 kg of CO2-eq/tonne of waste. According to these results, the current LFG-to-energy recovery project at Rachathewa landfill resulted in only 13% GHG reduction compared to the BAU practice, see Fig. 2. This result revealed that GHG mitigation from the existing LFGto-energy recovery project is not very impressive. Thus, design and operational changes are necessary to improve the efficiency of this kind of LFG recovery project in order to minimise GHG emissions and maximise the economic benefits. In order to quantify the GHG mitigation potential of an improved LFG recovery project, further analysis was performed to analyse an improved scenario, as seen in Fig. 3. According to this scenario analysis [9], if the gas recovery from the landfill in BMA could start in the second year while waste tipping continues (the sooner the LFG recovery project starts, the higher the electricity generation potential using the recovered gas) and gas extraction could continue throughout the 20 year peak production period, instead of the current 10-year plan, the highest LFG extraction rate could be achieved. However, additional generator sets need to be installed in order to optimise the recovery of LFG. In this improved scenario, 46% of GHG can be mitigated via electricity production and flaring as compared to the 13% GHG mitigation potential of the existing project. This example clearly shows the effects of sound management practices on the improvement of the overall efficiency of the project. Therefore, these kind of management practices should be carefully evaluated and incorporated into the project at the design phase. 3.1.2. Net GHG emissions from the incineration plant in Phuket Total GHG emissions from waste transportation in Phuket is 12 kg of CO2-eq per tonne of waste. It was noted that 60% of

Fig. 3. Amount of CH4 generation potential and CH4 avoidance potential from the current project and the improved scenario from Rachathewa sanitary landfill with gas recovery.

electricity generated by the incineration plant is used for operational activities. GHG emissions due to utilisation of fossil fuel for operational activities (e.g. utilisation of diesel fuel for initial combustion and co-firing to maintain flue gas temperature) was 0.63 kg of CO2-eq per tonne of waste. There are three types of waste, plastics, textile and leather/rubber, which could emit fossil based CO2 during the combustion process. According to the analysis, total fossil fuel based CO2 emissions per tonne of mixed MSW combustion would be 600 kg CO2-eq. Similarly a significant amount of CO2 could be emitted from the combustion of biomass materials (e.g. paper, food, and wood waste) and such biogenic origin CO2 is part of the carbon cycle [21] and was not accounted for in this study. Biogenic origin CO2 is usually treated as having no impact on climate change, as it is part of the natural carbon cycle. Such a distinction is essential since only a part of GHG emissions from incineration contributes to the climate change effect [23]. In addition, a small amount of N2O could be produced in the Phuket plant due to the favourable temperature range for N2O production (between 500
C-950
C) [21]. N2O based GHG emissions potential from the Phuket incineration plant would be 8 kg CO2-eq/tonne of waste. Taking into account all these GHG emissions, the estimated gross GHG emissions potential of the Phuket incineration plant is 620 kg of CO2-eq/tonne of combusted waste, see Fig. 4. As discussed earlier, only 40% of electricity generated (48 kWh/ tonne of collected waste) can be sold to the grid and that can be credited with avoiding the equivalent amount of conventional electricity production using virgin resources. The estimated GHG avoided due to the production of conventional electricity from waste (48 kWh/tonne of collected waste) amounts to 27 kg CO2-eq/ tonne of waste. The net GHG emissions from incineration were calculated by subtracting the avoided GHG emissions from the gross GHG emissions, which amounted to 593 kg of CO2-eq/tonne of combusted waste, see Fig. 4. The net impact was compared with BAU practice to understand the progress in Phuket. BAU practices in this study is sanitary landfill without gas recovery system. All the generated CH4 is directly escape into the environment and therefore BAU practice has shown very high GHG emissions potential. Despite low efficiencies of the current incineration plant, it accounted for a 55% reduction in GHG emissions compared to the BAU practice. 3.2. Estimation of environmental performance: net fossil resource consumption 3.2.1. Net fossil resource consumption from LFG to energy recovery project in BMA MSW collection and transportation, spreading and compaction at the landfill site consumed a considerable amount of diesel fuel at a rate of 9.7 L and 3.7 L respectively per tonne of waste management. Gross energy consumption from the project was estimated

Fig. 4. GHG emissions from the Phuket incineration plant in comparison with BAU practice.

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mainly with regard to those activities and this amounted to 11.63 kg of crude oil-eq/tonne of waste. The LFG-to-energy project in BMA consumed part of the electricity generated for on-site activities, but this is not accounted for in the analysis as it is considered as part of renewable energy. As a result of selling a part of the generated electricity to the grid (28.2 kWh/tonne), fossil-fuel utilisation for an equivalent amount of conventional electricity production could be avoided. Thus, electricity sold to the grid has been credited with avoiding an equivalent amount of conventional electricity production (5.95 kg of crude oil-eq/tonne). Taking into account all the aspects, the estimated net resource consumption from this project is 5.68 kg of crude oil-eq/tonne of waste management, see Fig. 5. A comparison of these results with BAU practice shows that an LFG to energy recovery project can lead to a 51% energy saving, see Fig. 5. According to the results of the analysis, it was noted that the LFGto-energy recovery project has a significant influence on the abiotic fossil resource savings. As mentioned previously, the current LFG-to-energy project is not very efficient. Improvements in the efficiency of LFG recovery through proper design and management practices could also significantly enhance the potential for fossil resource savings. For instance, the potential fossil resource savings from the improved scenario which was explained in the previous section (e.g. by initiating gas recovery from the landfill in the second year while waste tipping continues and gas extraction continues throughout the 20 year peak production period) would be four times higher than that of the current project.

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corresponding amount of conventional electricity production. Therefore, incineration contributed to net fossil resource savings, which is indicated by a negative value (6.25 kg crude oil-eq/ tonne), see Fig. 6. Furthermore, incineration technology contributes to significant energy savings as compared to BAU practice (sanitary landfill without gas recovery). All in all incineration technology has the potential to contribute to the growing renewable energy demand in a carbon constrained world. 3.3. Estimation of economic performance: net LCC

3.2.2. Net fossil resource consumption of the incineration plant in Phuket Waste collection and transportation is the major cause of fossil fuel consumption. Compactor trucks are mainly used for waste collection and transportation and the average loading capacity of a truck is 4 tonnes/trip. According to Phuket Municipality, fossil fuel consumption of the compactor trucks for collection and transportation is 4.25 L diesel/tonne. In addition, diesel fuel is used to enhance the initial combustion when re-starting the plant after periodic maintenance (two times per year) and as a supplementary energy source to maintain flue gas temperature. Total diesel fuel consumption for these operational activities equivalent to 0.23 L diesel/tonne. The plant has avoided utilising fossil-based conventional electricity for the operational activities with 60% of the electricity generated being used to operate the plant. The overall effect on total fossil energy consumption for incineration amounted to 3.89 kg crude oil-eq/tonne of waste. The remaining 40% of the electricity generated (48 kWh/tonne of collected waste) is sold to the grid, thereby avoiding virgin resource consumption (10.14 kg crude oil-eq/tonne) that would have otherwise occurred from the

3.3.1. Net LCC of the LFG to energy recovery project in BMA In order to assess the economic feasibility, all cost and revenue elements should be accounted for in a systematic manner. Therefore, total capital expenditure, operation and maintenance costs and revenue generation have been incorporated in the net LCC analysis. Land cost constitutes the major share of the capital costs (55%) for the existing LFG-to-energy project in BMA. This is followed by costs for construction of the landfill (including the liner and the leachate treatment system) (32%), purchasing a gas recovery and flaring system (5%), heavy machinery (4%), collection vehicles (2%) and the cost of site improvements (2%). Considering the total capacity of waste disposed of over a two year period, the estimated capital cost for the existing LFG to energy recovery project in BMA is THB481 per tonne of waste disposed (approximately THB32 ¼ USD1). As far as operation and maintenance (O&M) costs are concerned, the biggest share is attributed to waste collection and transportation, which is equivalent to 90% of the total O&M costs or 63% of gross LCC. The remaining 10% of O&M costs can be attributed to landfill management, especially to cover labour and fuel costs, repair and maintenance costs of the machines, landfill cover and leachate management system. In total THB1,103 was spent as O&M costs per tonne of waste management within the existing LFG to energy project in BMA. When including all the cost factors (capital costs and O&M costs), the estimated gross LCC is THB1,585 per tonne of waste management under the existing LFG to energy project, see Fig. 7. About 30% of this gross LCC is related to capital costs, and the remaining 70% to O&M costs. Possible revenues from the project should be accounted for in order to calculate the net LCC. Direct revenues could be earned in the form of a service fee that is collected from the households (THB20 per household per month) with this money being collected regardless of the existence of an LFG-to-energy project. Another option is the possible revenues from the sale of the electricity produced from LFG (THB5 per kWh) as well as the possibility of earning Certified Emission Reduction (CER) credits under CDM (the

Fig. 5. Net fossil resource consumption of the LFG-to-energy recovery project in BMA compared with BAU practice.

Fig. 6. Net fossil resource consumption of incineration plant in Phuket and the comparison with BAU practice.

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Fig. 7. Net LCC of LFG-to-energy recovery project and the comparison with BAU practice.

rate offered in 2011 for this project was EUR8 per tonne of CO2). By adding all these returns, the calculated life cycle revenue for the LFG-to-energy project is THB334 per tonne of waste, see Fig. 7. Out of this amount, 40% of revenue is from the fee collected from the households, 42% from selling the electricity produced by LFG to the grid, with the remaining 18% through CER credits from CDM. The net LCC was calculated by subtracting the above revenues from the gross LCC, it amounted to THB1,251 per tonne (see Fig. 7). However, the existing LFG-to-energy project contributed to a 12% net LCC cost reduction as compared to BAU practice. It should be noted that, notwithstanding all the possible revenue earnings, the BMA and Jaroensompong Corporation still have to bear significant expenses to run the current project. The revenue generated from the project alone has not been sufficient to cover the total costs and make the project commercially attractive. For instance, waste collection and transportation share the highest cost (63% of gross LCC) and therefore it is very important to improve the logistics in this area and reduce related costs. Furthermore, in order to earn more revenue and make this kind of project commercially attractive, it is necessary to increase the efficiency of the energy recovery process, extend the crediting period and extract LFG during the active period of the landfill.

3.3.2. Net LCC of the incineration plant in Phuket The net LCC of the existing incineration plant was estimated based on the real cost information related to collection and transportation, and incineration of waste. The estimated capital cost for incineration per tonne of collected waste amounts to THB470. The investment cost of the power plant accounts for 85% of the total capital cost, and the remaining 15% corresponds to the capital cost required to buy the waste collection vehicles. The total estimated O&M costs for the existing incineration plant is THB885 per tonne of collected waste. This accounts for 39%, 49% and 12% respectively if the total O&M costs are allocated among the costs that are required for collection and transportation, O&M activities at the incineration plant (including costs related to auxiliary materials, utilities, labour, pollution control, operating suppliers and insurance) and O&M costs for landfilling of residue waste (ash and non-combustibles etc.). By calculating all the cost components, the estimated gross LCC amounted to THB1,355 per tonne of collected waste. About 35% of this gross LCC is related to capital costs, and the remaining 65% to O&M costs. Furthermore revenue generated by selling part of the electricity generated (48 kWh/tonne of collected waste) is calculated as THB240 per tonne of collected waste. Then the net LCC was calculated by subtracting the revenues from the gross LCC and it was found to amount to THB1,115 per tonne of collected waste. The results of the analysis clearly indicate that incineration is an expensive MSW management method. The possibility of decreasing investment and O&M costs is very low as the incinerator

is imported and requires a considerable cost for proper maintenance. In the current situation, the revenue generated is not sufficient to make the project commercially attractive. Even the net LCC of incineration is 16% higher than that of BAU practice, see Fig. 8. Thus, an adequate amount of revenue earned by increasing the efficiency of energy recovery, and through earning CER credits, separation of recyclables prior to combustion etc. would be essential to make this kind of project commercially attractive. The management of the Phuket incinerator has not applied for CDM credits for GHG mitigation. According to the analysis of this study 55% of GHG can be reduced by applying incineration as compared to the BAU practice. Therefore, there is the possibility of applying CER credits and enhancing the potential for revenue generation. 3.4. Possible improvements for enhancing environmental and economic benefits of WtE technologies The analysis results of these case studies show the general situation of WtE plants in developing cities. WtE technologies have the potential to contribute to GHG mitigation, fossil resource savings and revenue generation. However, at the current level of operation, efficiency seems to be a critical factor that has greatly influenced the environmental and economic performance of these technologies. Compared to other MSW management technologies, sanitary landfill with gas recovery system is a low cost and easily manageable technology for cities in developing countries. There is a high possibility of initiating economically feasible LFG extraction projects in centralised landfills in cities like Bangkok. Similar to the case of BMA, most of LFG-to-energy projects shows inefficiencies due to inappropriate design and management practices. Proper design and operational plans are needed to improve the efficiency of LFG recovery, minimise GHG emissions and maximise energy recovery and economic benefits. As can be seen in Fig. 3, more than 80% of LFG would be produced during the first 20 years after landfill closure. Therefore, landfills should be designed so as to extract LFG during active operation of landfill or soon after closure. The sooner the LFG recovery project starts, the higher the electricity generation potential using the recovered gas. For instance, if the gas recovery started in the second year while waste tipping continues and installed right number of generator sets depending on the quantity of LFG available (3 MW IC engine for first 10 years and 1 MW engine for another 10 years), the highest extraction rate could achieved. In the improved scenario, 43% of generated CH4 can be mitigated via electricity production and flaring as compared to the 12% mitigation potential of the existing project. Such improvement in the efficiency of LFG-toenergy recovery projects could contribute to the country's GHG mitigation target, resource savings and currency savings due to both direct revenue generations and avoiding fossil fuel importation.

Fig. 8. Net LCC of incineration in comparison to BAU practice.

S.N.M. Menikpura et al. / Renewable Energy 86 (2016) 576e584

According to the analysis of the Phuket incineration plant, the results show the potential for GHG mitigation and fossil resource savings relative to BAU practice. However, the electrical efficiency of this incineration plant is limited to 8%. The composition (low calorific value of the waste) and moisture content of the waste have a great effect on the efficiency of the incineration plant [9,13]. Even after draining off a part of the moisture by leaving waste for 4e5 days in the waste pit, the moisture content of the combustibles remained at 40e42% and this leads to more energy being consumed to produce power from waste. In Asian cities, the majority of combustibles consist of organic waste which has lower calorific value. Further incineration plants in tropical Asia experienced lower efficiencies due to the effect of weather patterns on the characteristics of mix waste. At present, most of the city's organics are not effectively separated. Segregation of moist organic waste (e.g. restaurant waste, market waste) at source or at incineration plant would increase the calorific value of the residual waste in the incinerator. The separated fraction of organic waste can be utilised for compost or biogas production that would enhance the overall energy production efficiency from the waste management system. Even though such management practices would cause additional operational costs, it would enhance the net financial returns by improving the overall efficiency of energy production and resource recovery (though material recycling) potentials. Therefore, initiation of organic waste separation programme at source would facilitate developing cities to moving towards more sustainable waste management approaches like integrated waste management systems. As far as energy efficiency is concerned, most of the incinerators in Asia cities lack district heating systems to utilise the waste heat and recovery of waste heat would be an effective way to increase energy efficiency. If the waste heat can be recovered from the incineration plant, part of that can be effectively utilised to dry off the moist waste prior to combustion and the remaining can be exported to nearby facilities to replace conventional thermal energy sources. Furthermore, electrical efficiency can be increased by maintaining an appropriate steam temperature and pressure, temperature of the cooling agent used in the turbine's condenser and stable and robust operation practices. Lack of trained manpower for periodical operational and maintenance activities of WtE plants can be seen as another obstacle in developing Asia. Therefore, it is necessary to provide adequate training for the local technical experts to be able to repair and maintain these technologies if any breakdown occurs. With such improvements of technical and management aspects, efficiencies of incineration can be enhanced significantly and it would be a much better waste management option for obtaining adequate environmental benefits and financial returns. Further, improvement of the efficiency of the collection and transportation process (e.g. changing the collection routes using GPS, reducing the number of vehicles, reducing the idle time of the workers, improving the loading capacity of the vehicles etc.) would also be very important to enhance the efficiencies if WtE plants and then to receive more environmental and economic benefits. For instance, in the case of Bangkok, 63% of gross LCC used for waste collection and transportation, and this influenced the economic instability of the project. Initiation of efficient WtE technologies would be a possible solution in terms of reducing operating costs and subsequent tipping fees which are required for waste management in cities. In the meantime, the initiation of this kind of project would create other benefits such as creating employment opportunities to the local communities, reducing the local environmental pollution and increasing the esthetic value of the environment. However, one single technology cannot be the long-term solution for waste

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management problem in developing cities. Thus, point source separation of waste followed by biological treatment, recycling, incineration and landfilling of residue waste within a properly designed integrated system would be the most sustainable option as a long-term solution. All in all, this manuscript quantitatively analised and discussed the reasons for all kind of inefficiencies and failures of selected WtE facilities. Then the potentials for improving efficiencies through appropriate management practices, waste separation and recovery of resources etc. have been discussed. Therefore, the authors believe that learning through these failures /imperfect cases would give strong inspirations to the cities to avoid similar faults in their waste management systems. 4. Conclusion WtE systems evaluated in this study do not show very impressive results unlike the cases in developed countries. Both LFG-toenergy project in BMA and an incineration project in Phuket show the potential for GHG mitigation (13% and 55% respectively) and resource savings (51% and 190% respectively) as compared to BAU practice. However, financial returns from these projects are very low due to the low efficiency of energy recovery and high logistics costs (in the case of Bangkok). By adopting improved designs (e.g. initiation of LFG-to-energy recovery during the active phase of the landfill, using appropriately sized engines to extract LFG and maximising energy utilisation by cogeneration of heat and power) and improved management practices (e.g. point source separation of organic waste followed by biological treatment, and employing skilled labour to operate and maintain the incineration plant), efficiencies would be enhanced significantly. The results from this quantitative assessment could provide some important information for planning and implementing new WTE plants and enhancing the performance of existing plants in developing cities. In fact, learning through these imperfect cases would give strong inspirations to the cities to avoid similar faults in their systems. Acknowledgement The authors would like to thank the Bangkok Metropolitan Administration, the Jaroensompong Corporation, the Phuket Municipality and the management of Phuket incineration for their support during the field survey. The authors acknowledge the financial support from the Ministry of the Environment, Japan (MOEJ), under the project of MRV capacity building in Asia, for the establishment of new market mechanisms. References [1] A. Mavropoulos, Megacities Sustainable Development and Waste Management in the 21st Century, ISWA world congress, Hamburg, 2010. November 2010. Available in, http://www.scribd.com/doc/52389719/MetropolitanSustainable-Development-and-Waste-Management-in-the-21st-CenturyFull-Paper (accessed 25.05.13). [2] G. Mills, H. Cleugh, R. Emmanuel, W. Endlicher, E. Erell, G. McGranahan, E. Ng, A. Nickson, J. Rosenthal, K. Steemer, Climate information for improved planning and management of mega cities (needs perspective), Procedia Environ. Sci. 1 (2010) 228e246. [3] D. Hoornweg, P. Bhada-Tata, What a Waste: A Global Review of Solid Waste Management, Urban Development & Local Government Unit, World Bank, 1818 H Street, NW, Washington, DC 20433 USA, 2012. [4] U.N. Ngoc, H. Schnitzer, Sustainable solutions for solid waste management in Southeast Asian countries, Waste Manag. 29 (2009) 1982e1995. [5] S.N.M. Menikpura, S.H. Gheewala, S. Bonnet, C. Chiemchaisri, Evaluation of the effect of recycling on sustainability of municipal solid waste management in Thailand, J. Waste Manag. Biomass Valorization 4 (2) (2012) 237e257. [6] E. Stengler, Mega Cities Mega Challenges and Mega Opportunities, Waste Manag. World 13 (2) (2012). Available in, http://www.waste-managementworld.com (accessed 15.05.13). [7] D. Hoornweg, Megacities, Mega Opportunities, Waste Management World

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