A Comparative Analysis of CH 4 Emission Reduction from Municipal Solid Waste (MSW) under Different Scenarios in Kathmandu, Nepal

- Currently 516 tonnes of municipal solid waste per day are generated in Kathmandu, Nepal, the majority of which is taken to landfill. This is projected to rise to 745 tons per day by 2025. Landfill is a source of greenhouse gas emissions, most notably methane (CH 4 ). This study assessed the CH 4 emissions from a landfill site in Kathmandu for five scenarios: S0, S1, S2, S3 and S4. The results showed that CH 4 emissions are extremely high at 15,136 thousand m 3 for scenario S0 - “Business as usual”. A significant reduction of 53% of CH 4 emissions was achieved with gas capture (S1). Composting (S2) achieved a reduction of 35% reflecting the high organic content of waste that is currently landfilled. Recycling (S3) achieved a reduction of only 10%. Unsurprisingly, the greatest reduction in CH 4 emissions occurred with a combination of gas capture, composting and recycling (S4) with a 73% reduction. The results suggest that gas capture and composting are feasible alternatives. Recycling material should also be considered, as plastics may in the future take up a greater proportion of the waste material over time.

www.ijsrp.org (Japan International Cooperation Agency) in 2005 with a project life of 3 years but, as there is no alternative waste disposal site, the waste from Kathmandu valley is still being dumped there [17].
KMC is the focal organization accountable for handling the waste generated in KMC. A total of 1,320 staff are engaged to manage the solid waste [14] .These staff are spread across 32 ward offices, each has tractors or tippers and 20-30 sweepers, amounting to 927 street sweepers in total. Some private sector and Non-Government Organization (NGOs) also have sweepers to clean the streets.

Study area
The study area Kathmandu Metropolitan City (85° 20' East and 27° 42' north) lies in Kathmandu Valley of Nepal. It covers an area of 50.67 km 2 . The elevation of Kathmandu lies 1,350 meters above mean sea level [18]. The Kathmandu valley has a mild climate most of the year with summer temperatures ranging from 19-27°C, and winter temperatures ranging from 2-20°C. Total annual rainfall in the area is 1,505 mm with around 80% rain occurs during rainy season (June to August) [19]. The Kathmandu City is divided into 5 major sectors and 32 wards as the decentralized units as shown in Error! Reference source not found.   [20] In the last 20 years the population of the city has grown at an annual growth rate of 4.8% from 0.67 million in 2001 to 1.0 million in 2011 [21] . Due to rapid population growth and urbanization the quantity of waste generated in Kathmandu city is increasing rapidly, demanding special attention for proper Solid Waste Management (SWM). Figure 3 shows that there is a strong linear relationship between waste generation and population with coefficient of regression R 2 = 0.99. Based on this regression waste quantity by 2025 is predicted to be 271,965 tonnes. ISSN

Framework for Research Methodology
The framework for the research methodology is shown in Figure 4. In Phase 1 Life Cycle Assessment (LCA) is proposed as the key research strategy. The principles and framework for LCA include defining the goals and scope, Life Cycle Inventory (LCI) analysis, Life Cycle Impact Analysis (LCIA) and Life Cycle Interpretation [23]. In view of the structure of LCA, the objective and extent of the investigation will be re-imagined. Likewise, predictive scenarios will be structured, and discharge stock techniques will be chosen.
Most of the calculations will be made based on Inventory Analysis, as the purpose of the study will be to analyse potential environmental benefits through alternative scenarios. The focus of the scenarios is on the current situation in Kathmandu and potential future waste treatment facilities which fit with the waste characteristics of Kathmandu targeting less energy consumption, low emissions whilst being cost effective with maximum social benefits acceptable to society.
Phase 2 involves emission accounting and evaluates CH 4 discharges by utilizing two numerical models: IPCC default; and first order decay (FOD) model [24]. The results for every situation are then evaluated and compared to determine the best MSW management for Kathmandu in regards to reducing GHG emissions.  MSW in KMC is collected waste without segregation at the source, mixed with other waste and conveyed to Sisdole landfill site. The existing Sisdole landfill site, however, is overloaded. Accepted Government policy is focused on improving MSW management systems, especially, with the rate of increase in food waste and recyclable components in MSW. This has led to some segregation of food waste and inorganic waste at source to be treated by composting and recycling, rather than landfill.
The five scenarios proposed in this study with system boundaries are illustrated in Table I Table II [15], [16], [14]). The waste composition data of the year 2015 is considered for the calculation in this study work. Upgrade of Landfill gas capture (S1) The landfill gas capture scenario is the same as S0 but assumes 70% of CH 4 gas is gathered. Landfill gas (LFG) is naturally produced by the decomposition of organic materials (also known as biomass) and increasing moisture content can accelerate the waste decay process. The rate of LFG production thus also increases with moisture content, peaking at waste moisture contents of 60 to 78% [25].
Sisdole landfill waste has an average moisture content of about 35.3 %, with a high volume of food and vegetable waste having a higher moisture content [26]. After waste placement, rainfall, surface water and groundwater infiltration, together with the products of waste breakdown, can contribute additional moisture. Based on these existing conditions, and observations of existing vent pipe placements to allow methane gas to escape alongside discussion with KMC staff, this scenario assumes that the introduction of a gas ISSN 2250-3153 www.ijsrp.org capture system will be effective at gathering 70% of the gas produced (R=0.7). Other parameters in the scenario are the same as S0.
The estimation of the model parameters for scenario S1 are shown in Table 3.

Composting of organic waste (S2)
In this scenario the composting of 50% of organic waste from 86.9% of the landfilled waste is isolated, gathered and composted with the remaining waste sent to landfill. This figure is based upon discussions with KMC staff on the feasibility of the process. In this scenario using input data, 50% of organic waste is identical to 51,743 tons of the 103,486 tons of organic waste which can be treated as compost. The adjustment in the waste amount and level of the waste composition for the input scenario S2 are shown in Table 3.

Recycling prior to landfill (S3)
Based on the study of Kathmandu solid waste management Bank [15], 25 % of household waste and a much higher proportion of institutional and commercial waste could be either reused or recycled. This is excluding organic waste. This scenario therefore assumes that 25% of the MSW from the amount of buried MSW, including paper, metals, glass, plastic, construction and demolition waste, and textiles is separated at the source and recycled with the remaining waste sent to landfill. It is assumed that a similar measure of MSW, with a similar composition as in S0 is covered. The adjustment in the waste amount and level of the waste composition for the input scenario S3 are shown in Table 3.

Integration of capture, recycling and composting (S4)
Firstly, 50% of organic waste from landfilled MSW will be gathered and treated by fertilizing the soil to make compost in S2.
Moreover, recyclable materials, for example, paper, metals, glass, plastic, wood and material will be recycled at a 25 % rate in the material recycling facility. The remaining waste is sent to the landfill. Lastly, in assumption S0, 70% of CH4 emissions will be collected and recovered. The same amount of MSW, with the same composition in S0, is delivered and treated at the landfill site.

System boundaries
The practical unit in this examination is the aggregate sum of waste produced in KMC in a year, i.e. household, commercial, and institutional. This amounts to 163,666 tons in terms of solid waste collected. The functional system boundaries selected for this LCA only includes the direct emission from the waste after landfill where waste was characterized as the minute when material stops to have value.
In this examination, figure 5 presents the key points for each scenario for the MSW management system in Kathmandu. The upstream limit begins with MSW being dumped in the landfill site. The procedure of collection and transport is excluded in the framework stream for all scenarios. It is on the grounds that it is hard to recognize and isolate the GHG outflows produced from the collection and the transportation that might be conveyed to either landfilling or other treatment destinations.
Unit procedures incorporated into the emissions scenarios are: (1)  www.ijsrp.org   Where, DOC is degradable organic carbon, A: fraction of paper and textiles; B: fraction of garden waste and park waste; C: fraction of food wastes and D: fraction of MSW as wood or straw.
Applying measurable information on waste composition in the KMC MSW, the level of DOC in MSW is 14.1%. This figure is for scenario S0 and S1. In contrast with S0 and S1, the estimations of DOC applied to the remainder of the scenarios are 13.7% for S2, 14.1% for S3 and 13.69% for S4 (Table 3).

Fraction DOC dissimilated:
This is the DOCF that is changed over to LFG. The theoretical model is linked to the temperature in the anaerobic zone of a landfill site. The model is depicted as 0.014T+0.28, where T=temperature in ˚C [27]. It is expected that temperature stays steady at 35˚C in the anaerobic zone of the landfill. This results in a figure of 0.77.

Fraction of methane (F) in LFG (default is 0.5):
The division of methane in LFG is expected to be 0.5, and is the figure used here.

R (Recovered methane) (Gg/year):
Recovery of LFG does not yet take place in Nepal. For scenario S1 and S4 it is assumed that if a gas capture system is introduced it would be effective at collecting 70% of the gas produced (R0.7). Additionally, using a landfill top cover of soil the default parameter for the oxidation factor will be 0.1 [13]. where R is the annual precipitation , the calculated value of k is 0.06 and corresponding t1/2 is 10 years.  (Table IV).

Waste composition under different scenario in KMC
For S0 and S1 scenarios, the MSW in Kathmandu contains a high extent of organic waste, representing over half (63.23%) of the landfilled waste. Similar levels are seen in scenario S3 with 69.04% of organic waste. On the other hand, scenarios S2 and S4 have a lower extent of organic waste (46.23% and 52.72% individually), they additionally have the highest level (percentage) of gradually degrading waste (paper, material, plastic, glass and metal). This determines the varying levels of CH 4 outflows and also the age of the landfill in every scenarios. For Scenarios S2, S3 and S4 there will be a change in the aggregate sum of waste sent to landfill with the expansion of composting in S2, in recycling for S3 and both composting and recycling in S4. Figure 6 illustrates the tonnage composition for each scenario.

Potential methane (CH4) emissions
The potential outflows of CH 4 from the Sisdole Landfill site using the IPCC default model varies between the five scenarios as shown in Table V   respectively. The only difference is that in scenario 1 the waste is used to generate gas through the 70% gas capture system. In scenario S0, there is no gas capture and mixed waste is directly disposed as usual. In scenario 2, the volume of the waste decreases to 111,923 tonnes per year due to more recycling of recyclable materials and recovery of organic materials. In scenario 4 Furthermore, the volume of landfill waste decreases to 98,151tonnes in scenario 4. This is due to 50% of compost recycling, 70% of methane recovery at the landfill and 25% inorganic waste recycling as integration method.   Figure 9. The assumption made in DM is that the potential methane is emitted in the same year that waste is deposited.
This may not be realistic. The values used in the FOD model are based on the assumption that the gas generation takes up to 13 years to take place. Although it appears that the FOD model shows lower emission than the DM model, what is not taken into account in this analysis is the emissions that will occur as a result of previous waste deposition as this has not been calculated here. This should be taken into account in the following analyses.  Figure 10, where scenario S0 and S1 overlaps since same volume of waste are disposed in landfield under these scenario. It is also assumed that the degradation takes place in two stage.

IV. CONCLUSION
This research was carried out to determine the Kathmandu Metropolitan City (KMC) solid waste management system which has the potential to achieve the greatest reduction in methane (CH 4 ) emissions based on the five suggested scenarios developed for the study: S0, S1, S2, S3, and S4, where is S0 is Business as usual and other are alternative scenarios tested to reduce CH4 emission. The scenarios were tested using the Life Cycle Assessment (LCA) tool alongside the default and first order decay methods as suggested by Intergovernmental Panel on Climate Change (IPCC), and methane emissions under different scenarios were compared.
The results showed that CH 4 emissions are extremely high at 15,136 thousand m 3 for scenario S0 -"Business as usual". A significant reduction of 53% of CH 4 emissions is achieved with gas capture (S1). Composting (S2) achieves a reduction of 35% reflecting the high organic content of waste that is currently landfilled. Recycling (S3) only achieves a reduction of 10%. Unsurprisingly, the greatest reduction in CH 4 emissions occurs with a combination of gas capture, composting and recycling (S4) with a 73% reduction.
The NV Afvalzorg model simulations demonstrate that production of CH 4  www.ijsrp.org Given the current composition of waste that is deposited at Sisdole landfill site, it is suggested that the feasibility of gas capture and composting is investigated as alternatives. Recycling material should also be considered long term as plastics and similar may in the future take up a greater proportion of the waste material over time.