Scholarly article on topic 'Opportunities & Challenges in Capturing Landfill Gas from an Active and Un-scientifically Managed Land Fill Site – A Case Study'

Opportunities & Challenges in Capturing Landfill Gas from an Active and Un-scientifically Managed Land Fill Site – A Case Study Academic research paper on "Earth and related environmental sciences"

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Abstract of research paper on Earth and related environmental sciences, author of scientific article — R.K. Kashyap, Parivesh Chugh, T. Nandakumar

Abstract Currently, nearly 210 Million Metric Tonnes/Annum of Municipal Solid Waste (MSW) is generated in India and most of it gets disposed in Open and un-scientifically managed Landfills. The typical Indian MSW contains approximately 50% of bio-degradable organic components that starts degrading under anaerobic conditions and generates LandFill Gas (LFG). The LFG mainly contains Methane (40-50%) and CO2 (50-60%). Methane is a Green House Gas (GHG), and is 25 times more potent than CO2 in causing Global Warming and is the 2nd largest anthropogenic source of Methane emissions after coal mining. Thus capturing and destructions of LFG shall lead to mitigation of GHG emissions. In addition, open Landfill sites also pose safety risks like fire hazard, explosion, and asphyxiation etc. apart from health risks. At the current MSW generation rate of 0.575MMT/day in India, the LFG generation potential is around 86.25 MMSCMD of LFG. Presently, LFG from the landfill sites is not being captured leading to fugitive GHG emissions. Further, due to rapid population growth and accompanying urbanisation and lack of new landfill sites, the existing waste handling infrastructure is getting stressed and leading to overflowing and vertical growth of the existing landfills. Thus Indian landfills provide good opportunities for the extraction & utilisation of Methane from LFG. However, there are lot of Issues that need to be overcome for exploitation of LFG in a sustainable manner. GAIL (India) Ltd, a Maharatna company, as a part of its R&D activities has taken up an initiative in this direction and implemented a Pilot project to ascertain the recovery of LFG from an un-scientifically managed open active MSW dumping site at Ghazipur Delhi. The utilization of LFG for energy recovery is being explored. This Paper shares the Challenges faced and Key insights gained during the LFG Project Implementation and its Operation.

Academic research paper on topic "Opportunities & Challenges in Capturing Landfill Gas from an Active and Un-scientifically Managed Land Fill Site – A Case Study"

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Procedia Environmental Sciences 35 (2016) 348 - 367

International Conference on Solid Waste Management, 5IconSWM 2015

Opportunities & Challenges in Capturing Landfill Gas from an Active and Un-scientifically Managed Land Fill Site - A Case Study

R.K Kashyapa\ Parivesh Chughb, T. Nandakumarc

aExecutive Director (R&D & TQM), GAIL (India) Ltd., Noida, India bDeputy General Manager (R&D), GAIL (India) Ltd., Noida, India c Senior Manager (R&D), GAIL (India) Ltd., Noida, India

Abstract

Currently, nearly 210 Million Metric Tonnes/Annum of Municipal Solid Waste (MSW) is generated in India and most of it gets disposed in Open and un-scientifically managed Landfills. The typical Indian MSW contains approximately 50% of biodegradable organic components that starts degrading under anaerobic conditions and generates LandFill Gas (LFG). The LFG mainly contains Methane (40-50%) and CO2 (50-60%). Methane is a Green House Gas (GHG), and is 25 times more potent than CO2 in causing Global Warming and is the 2nd largest anthropogenic source of Methane emissions after coal mining. Thus capturing and destructions of LFG shall lead to mitigation of GHG emissions.In addition, open Landfill sites also pose safety risks like fire hazard, explosion, and asphyxiation etc. apart from health risks.

At the current MSW generation rate of 0.575MMT/day in India, the LFG generation potential is around 86.25 MMSCMD of LFG. Presently, LFG from the landfill sites is not being captured leading to fugitive GHG emissions. Further, due to rapid population growth and accompanying urbanisation and lack of new landfill sites, the existing waste handling infrastructure is getting stressed and leading to overflowing and vertical growth of the existing landfills. Thus Indian landfills provide good opportunities for the extraction & utilisation of Methane from LFG. However, there are lot of Issues that need to be overcome for exploitation of LFG in a sustainable manner.

GAIL (India) Ltd, a Maharatna company, as a part of its R&D activities has taken up an initiative in this direction and implemented a Pilot project to ascertain the recovery of LFG from an un-scientifically managed open active MSW dumping site at Ghazipur Delhi. The utilization of LFG for energy recovery is being explored. This Paper shares the Challenges faced and Key insights gained during the LFG Project Implementation and its Operation. © 2016Published byElsevier B.V. Thisisan openaccess article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of 5IconSWM 2015

* Corresponding author.

E-mail address:rkkashyap@gail.co.in

1878-0296 © 2016 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of 5IconSWM 2015

doi: 10.1016/j.proenv.2016.07.015

R.K Kashyap et al. /Procedia Environmental Sciences 35 (2016) 348 — 367 Keywords:Land Fill Gas (LFG), Energy Recovery, Microturbine, GHG;

1. Introduction

Millions of Tons of Municipal Solid Waste (MSW) is generated daily across the world. The MSW is disposed off in landfill sites. The MSW starts degrading under anaerobic conditions and generates Land Fill Gas (LFG). The LFG principally contains Methane (40-50%) and CO2 (50-60%)and other minor constituents like H2S in ppm level apart from few micro constituents. The Developing countries are disposing their MSW in open dump yards (which are not scientifically managed) leading to uncontrolled emissions of LFG to atmosphere. The Methane in the LFG is a potential Green House Gas (GHG), considered 25 times more potent than CO2 in causing Global Warming. Methane emissions from waste handling are the 2nd largest anthropogenic source of Methane emissions after coal mining and nearly 1.5 percent of global warming is related to emissions from landfills (IEA, 2009). Apart from the global emission effect, these emissions have a local environmental impact on air quality at landfills and in the surrounding areas.Thus capturing of LFG for energy recovery or destructing it by combustion shall lead to mitigation of GHG emissions. In addition, open Landfill sites havesafety risks like fire hazard, explosion, and asphyxiation etc. apart from health risks. GAIL had taken up a Project to capture LFG (in Phase-1) at Ghazipur Landfill site in Delhi and purify it for use as CNG (in Phase-2). This Paper shares the key insights gained during the LFG Project execution.

2. LFG Generation Process:

LFG generation process consists of complex series of biological and chemical reactions as the refuse decomposes. The earlier studies indicate that at least four types of decomposition happens :(i) An Initial aerobic phase; (ii) An aerobic acidic phase;(iii) An initial methogenic phase and (iv) A final stable methogenic phase(Farquar and Rovers,1973). As the waste is initially dumped at the site it undergoes aerobic digestion leading to depletion of Oxygen and production of CO2. This phase extends only for a brief period as the waste is being dumped continuously and compacted. The bottom lying waste starts getting subjected to anaerobic condition and supports fermentation reaction. The biodegradable organic constituents of waste are subjected to three types of bacterial actions: (i) Hydrolytic and fermentative bacteria hydrolyze polymers and ferment the resulting monosaccharidestocarboxylic acids and alcohols;(ii)Acetogenic bacteria convert these carboxylic acidsand alcohols to acetate, hydrogen and carbon dioxide; and (iii) Lastly, the methanogenicbacteriaconvert the end products of the acetogenic reactions to methane and carbon dioxide. The above reactions of LFG generation are greatly influenced by the field conditions like the actual composition of organic waste, moisture in the landfill, compaction level, ambient temperature etc. (González et al, 2011). Various theoretical & experimental studies report generation of around 100-200 M3 of LFG per tonne of waste with 60% of bio-mass content. Considering a Methane content of 50% in LFG, the methane generation potential works out to 50-100 M3/Tonne of MSW (Siddiqui, F. Z., et al, 2013).

3. MSW management In India:

Currently, nearly 210 million metric tonnes annum of MSW is generated in India & most of it is disposed in open landfills. The typical Indian MSW contains 50% of organic biodegradable components, 20% of recyclable portions, 22% inerts and others 8%. The biodegradable waste is contributed by food &yard waste. It is estimated that the level of per capita waste generation in India is 0.1kg, 0.3kg & 0.5 kg for small, medium and big cities respectively and is expected to grow at a rate of 1.3% per annum. Most of this collected waste (>90%) is not processed and gets disposed off in landfills that are not scientifically managed & lack safe disposal practices like landfill compaction, soil covering etc.( Siddiqui, F. Z., et al, 2013).Rapid population growth and accompanying urbanisation is putting huge pressure on the existing waste handling infrastructure. New landfill sites could not be developed due to acute scarcity of land. Consequently, Urban Municipal Bodies are not able to improve their waste management system which is leading to overflowing and vertical growth of the existing landfills. The LFG generated in these landfills is not being captured and utilised for energy recovery or destroyed for GHG mitigation.

4. Energy Potential of Indian Landfills:

Estimation by International Energy Agency (IEA, 2009) studies indicates that the methane emissions from Indian Landfill sites is around 16 Million tonnes of Carbon Dioxide equivalent (CO2e) per annum and is predicted to rise to 20 Million tonnes ofCO2e by 2020. These studies also show that Methane emissions from the Indian landfill sites are the second largest after the coal mining activities. The United States Environmental Protection Agency (USEPA) carried out a study in 2009 at Ahmadabad, Delhi, Hyderabad, Mumbai & Pune landfills and estimated that the combined emissions reduction potential of these landfills is around 3,00,000MT of CO2e. FICCI had conducted a survey among 48 cities and based on the response of 22 cities indicated that maximum potential for LFG recovery exists in Delhi, Mumbai, Kanpur, Jaipur, Pune, Surat, Ludhiana and Ahmadabad. Due to tropical climate in India, waste decomposition is much faster compared to the temperate countries and thus the landfills reach stable methogenic stage very quickly once the landfills are compacted and start producing appreciable amounts of LFG within 1 to 3 years. Almost all LFG gets produced within 20 years after the waste is dumped; however, small quantities of LFG may continue to be emitted for 50 or more years. Considering the current MSW generation rate of 0.575MMT/day with 60% organic content, waste collection efficiencies of 60% and 90 % of it being dumped in landfills, the estimated generation potential will be around 86.25 MMSCMD of LFG. Thus Indian landfills provide huge opportunities for the extraction & utilisation of methane from LFG (Ramani et al, (2011). However, there are lot of challenges that need to be overcome for achieving this. GAIL (India) Ltd, a Maharatna company, as a part of its R&D activities took an initiative to implement a Pilot project to ascertain the recovery of LFG from an unscientifically managed open active MSW dumping site.

5. GAIL's LFG Pilot Project:

GAIL entered into an MoU with MCD for implementation of LFG Pilot project. MCD earmarked 4 Hectares of Landfill site out of 29.6 Hectares at the Ghazipur landfill site for the Pilot project. The objective of the Pilot project was to assess the potential of LFG recovery from an active Landfill site (in Phase-1) and study the suitability of its use as an alternate renewable fuel source by purifying it for use as CNG (in Phase-2).

5.1 Ghazipur Landfill Site:

Ghazipur landfill site (28037' 22.4'' N and 77019' 25.7'' E) was commissioned in year 1984 and spreads over an area of 29.62 Hectares (Figure-l).About 85% of the site is covered with waste. The MSW accumulation at the Ghazipur has reached a maximum height of about 30m and an average height of about 25m above ground level with average side slope of 70°. The total accumulated waste at this site is estimated at 4.7 Million Tonnes. This is an active landfill site and on an average, 450 trucks haul about 2100 Metric Tonnes of MSW to this site daily.

The site does not follow any landfill management system except daily spreading and compaction of waste. Due to the presence of poultry market, fish market and a slaughter house towards its northern boundary, a significant amount of animal waste is also dumped here. The Hindon canal is on the East side of the landfill and is separated by a road.

The Ghazipur site is very close to habitation. It is surrounded by DDA Janta flats and Ghazipurdairy farm on its West, high income multi-storied residential areas of Vaishali, KaushambiandNeelamViharon its North and Kondli, Rajveer colony, MayurVihar-III etc. towards its South, all within one km distance.

The dumpsite may be termed as an un-scientific solid waste disposal facility without any LFG collection system. Consequently, there is an unabated emission of LFG into the atmosphere.

Fig. 1. Satellite image of Ghazipur Landfill site

5.2 GAIL's Pilot Project Area:

GAIL's R&D Pilot project area comprises of 4 Hectares (10 Acres) in the North-Eastern part of the Ghazipur Landfill site. The area can be subdivided into three parts - Slice A, Slice B & slice C (Figure-2).A detailed topographical survey of the earmarked site was carried out.Based on the topographical survey, the natural topography and elevation of the area wasobtained and the quantity of waste accumulated above ground level was estimatedat 0.45 Million Tonnes which is about 10% of the total accumulated waste of Ghazipur.

Fig. 2. Satellite image of Pilot Project Area

5.3 Waste Characterization:

Waste composition is an important consideration in evaluating a LFG recovery project, in particular the organic content, moisture content, and "degradability" of the various waste fractions. Waste characterization study was carried out on waste samples for specific physical and chemical parameters. Five samples of fresh waste and six samples of accumulated waste were taken at a depth of 5m, 10m and 15m using 500mm bore hole and the details are indicated in the Table - 1&2.

Table l.Characterization of Fresh Waste

Parameters Unit 1 2 3 Samples 4 5 Avg

Moisture Content % 80.5 87 44.54 40.36 16.1 53.7

Density Kg/m3 420 980 520 590 700 642

Physical Composition

Wood and wood products, A Pulp, Paper and cardboard, B Food, food waste, beverages and tobacco, C Textiles, D % % % % 2.50 3.13 62.97 16.00 4.00 7.00 64.50 10.50 3.50 4.30 61.70 18.00 2.00 3.50 66.50 12.00 13.00 5.30 68.0 6.70 5.00 4.65 64.73 12.64

Garden, yard and park waste, E Glass, Plastic, Metal and other inert matter, F % % l.50 13.90 2.00 12.00 3.00 9.50 4.50 11.50 3.50 3.50 2.9 10.08

Table 2. Characterization of Accumulated Waste

Parameter Unit 500 mm borehole (Set1) 5m 10m 15m 5m 500 mm borehole (Set2) 10m 15m

Odour - Foul Foul Foul Foul Foul Foul

Colour - Black Black Black Black Black Black

Density Kg/m3 480 590 620 436 441 540

Moisture content, air dried % 40.6 51.6 55.6 48 48.6 49.6

Org content, 105°C, oven % 38 21.4 18.5 42 40 36.8

5.4 LFG Pump tests:

LFG Pump tests were carried out to estimate the potential for LFG recovery. The testing Methodology outlined in "USEPA CFR Test Method 2E —Determination of LFG Production Flow Rate procedures" was followed (US EPA, 2010). The objectives of the Pump test were:

1) To determine the optimum conditions of LFG flow rate and its composition under static & dynamic conditions;

2) To measure vacuum (pressure) and flow relationships while actively extracting LFG from the Landfill.

3) To measure sustainable Methane levels in the extracted LFG during the test pumping.

4) To measure vacuum (pressure) in probes to estimate the lateral vacuum influence of the active test pumping.

5) To measure oxygen levels of the extracted LFG during the test pumping to checkfor air infiltration through the soil during test pumping.

6) Utilize the results of the pump test to refine the projections of LFG recovery.

Three main LFG extraction wells of 500mm bore dia.& 15 m depth were installed with minimum spacing of 40m from each other in the earmarked area. Each set has one main LFG extraction well surrounded by 9 monitoring

wells drilled along three directions at 120o apart from the main extraction well at the distance of 3, 15 and 25m respectively. The bore dia. &depth of monitoring wells was kept as 250mm and 10 m. The schematic diagram of main well is indicated in Figure-3:

Fig. 3. Schematic Diagram of LFG Well

All wells were interconnected and connected to a Blower to measure the LFG flow rate. Flow control valves were installed at each extraction well as well as at the Blower inlet for adjustment of vacuum and flow for overall system as well as for individual wells.

5.4.1 Static /Passive Testing:

The objective of Static testing is to get an idea of the LFG emissions under Baseline scenario. Therefore, the gas flow rate from the extraction was measured under atmospheric pressure without operating the suction Blower. Static tests were performed for each set of the borehole and various parameters were measured at hourly interval. The mean flow rate observed during the static test was 0.9 m3/Hr with 45.7% CH4 content. Static pressure readings were within normal range. The positive pressure observed in Main well indicated LFG pressure build-up and LFG generation.

5.4.2 Active Testing:

Active testing of LFG Pump test was carried out in Jan-2010. Oxygen content of more than 15% was observed during dynamic testing indicating air ingress. Even after attending leaks in the

pipe system, O2 content was high which indicated that the soil compaction layer was not proper and this could only

be improved by providing an impervious layer during actual closure of landfill. Under these conditions, the monitoring probes exhibited a negative probe pressure. This is a clear indication that the probes were within the "zone of influence" of the extraction well. The average flow rate observed during the passive & active test is indicated in Table-3:

Table 3. Flow rate during Passive and Active Tests

Volumetric Gas Gauge Atm.

n io Composition (%) Pressure Vel. Pressure Gas

■o n o U CH4 O2 CO2 mm mm Hg H2O (m3/hr) (m/s) mm kPa „ Hg Temp. (°C)

Static 45.7 1.5 29.1 0 0 0.91 0.01 97.24 279.3 15.5

Dynamic 15.67 18.8 2.47 -22.65 -307.28 16.43 0.26 96.8 725.9 14.7

As discussed above, there is evidence of vacuum influence extending to shallow probes up to 25 m from each of the extraction wells. Based on this, it is estimated that the radius of influence of theex traction wells is 25 m.

It may be noted that the LFG Pump test was conducted under the existing site conditions of high leachate levels and absence of impervious cover which adversely affected the LFG flow rate and its quality, in terms of methane content. It was expected that once the Project area is properly closed by providing impervious cover and a system is implemented to reduce the leachate levels, the extracted quantity and quality of LFG will significantly improve.

Using an estimated well radius of 25m, and a waste depth of approximately 20m, the volume of influence of the pump test is estimated to beabout 12,500 m3. Taking into account these facts, the expected LFG flow rate would be around 820-900 M3/Hr. With the gas collection efficiency of 60%, it was expected to obtain LFG flow rate of 500-550M3/Hr in the earmarked area.

5.5 Estimated LFG Potential:

LFG production potential for a typical waste disposal site is highly variable and affected by a number of local conditions, site design and operational features. A LFG mathematical model based on IPCC's (Intergovernmental Panel on Climate Change) First Order Decay (FOD) was used to project the LFG recovery from Base line scenario for a period of 15 years. This method assumes that the Degradable Organic Carbon (DOC) in the waste decays slowly throughout a few decades, during which CH4 and CO2 are formed. If conditions are constant, the rate of CH4 formation depends solely on the amount of carbon remaining in the waste. Therefore, the CH4 emissions from the waste deposited in a landfill are highest in the first few years after closure and then gradually start reducing.

As per the IPCC's FOD Model, the amount of methane that is generated each year (BE CH4, SWDS,y), (t CO2e) is calculated for each year y, using the following equation:

BEcm.s*w,. =<p (X~f) GWPCB, {\-OX)l^- F DOCf Jl/CF l\x DOC (1-e"*')

Where,

1) BE CH4,SWDS-Methane emissions avoided during the year y from preventing waste disposal at the Solid Waste Disposal Site (SWDS) during the period from the start of the project activity to the end of the year y (tCO2e)

2) ^ -Model correction factor to account for model uncertainties

3) f-Fraction of methane captured at the SWDS and flared, combusted or used in another manner

4) GWPCH4 -Global Warming Potential (GWP) of methane, valid for the relevant commitment period

5) OX-Oxidation factor (reflecting the amount of methane from SWDS that is oxidised in the soil or other material covering the waste

6) F-Fraction of methane in the SWDS gas (volume fraction)

7) DOCf-Fraction of Degradable Organic Carbon (DOC) that can decompose

8) MCF-Methane Correction Factor

9) Wj,x -Amount of organic waste type j prevented from disposal in the SWDS in the year x (tons)

10) DOCj-Fraction of Degradable Organic Carbon (by weight) in the waste type j

11) Kj-Decay rate for the waste type j

12) j-Waste type category (index)

13) x-Year during the crediting period: x runs from the first year of the first crediting period (x = 1) to the year y for which avoided emissions are calculated (x = y)

14) y-Year for which methane emissions are calculated

The values for correction factors used in the Model are mostly default values suggested by IPCC. Further, IPCC has recommended default k values for different waste categories dependent upon the location of the landfill site and its climatic conditions. Delhi is located in tropical area with a Mean Annual Temperature of 34°C (range of 8°C to 40°C) and Mean Annual Precipitation of 797 mm. Therefore, the IPCC default values of k for dry conditions, are presented in Table-4 :

Table 4. IPCC default values of k for dry conditions

Type of Waste K

Wood and wood products, A 0.025

Pulp, paper and cardboard, B 0.045

Food, food waste, beverages and tobacco, C 0.085

Textiles, D 0.045

Garden, yard and park waste, E 0.065 Glass, plastic, metal other inert, F 0

As the waste was deposited in the earmarked area as recently as 2007, the average composition of fresh waste indicated in Table -1 was considered for calculation. Using the input parameters as described above, FOD modelling projections of CH4 emissions for 15 years (2012-26), assuming 2012 to be the first year of closure were made and are indicated in Table-5 for three possible scenarios of methane concentration at 50%,40% & 30%. The results obtained from the Model were compared with the LFG pump test carried out at site to establish some realistic estimates and was comparable with the scenario with 30% Methane content.

5.6 Project Registration as CDM Project under Kyoto Protocol:

The capturing of LFG and its utilization as fuel helps mitigate the GHG emissions on 2 counts.

The first reduction of GHG happens during its collection and Flaring as the CH4 is destructed to CO2 (as CH4 is 25 times more potent than CO2 for causing Global warming). The second reduction happens while using LFG as Fuel as it replaces the fossil fuels. Both these counts are eligible for earning Carbon Emission Reduction (CER) units.

As this Pilot project was not financially viable, therefore it was eligible for registering as a Clean Development Mechanism (CDM) Project under Kyoto protocol. As per UNFCCC guidelines the Project can be qualified as CDM Project for earning CERs on the following Methodologies:

1) AMS-III, G, Version 8: Recovery of LFG and

2) AMS-III, AQ, Version 1: Use of LFG as CNG

Based upon the estimated LFG Flow rate, CER traded price of US $16, Exchange rate of 1 US$ = Rs.48, the total value of CDM credit was estimated at Rs. 28 crores over a Project life of 15 years.

The prior consideration for availing CDM benefit was intimated to UNFCCC &MoEF. A Public stake holder consultation meet was organized in Nov-2012 for explaining the overall benefit of the project to the local populace. MoEF has accorded host country approval for the Project in Aug-2013. The project is under validation by Designated Operating Entity (DOE). The CDM benefit thus allows critical funding for bridging the viability gap for execution of such sustainable projects.

Table 5. CH4 generation potential for different scenarios

Year LFG Flow Rate, m3/hr CH4Flow Rate, m3/hr

at 60% capture Methane Content 50% Methane Content 40% Methane Content 30%

2012 607 304 243 182

2013 566 283 227 170

2014 528 264 211 159

2015 493 247 197 148

2016 461 230 184 138

2017 430 215 172 129

2018 402 201 161 121

2019 376 188 150 113

2020 352 176 141 106

2021 330 165 132 99

2022 309 154 123 93

2023 289 145 116 87

2024 271 136 109 81

2025 255 127 102 76

2026 239 119 96 72

5.7 LFG Pilot Project Implementation:

As there was uncertainty in implementing this first-of-a-kind Project, it was decided to implement the Project in 2 Phases viz.( GAIL (India) Ltd, 2010).

1) Phase-1 -Involving scientific closure of landfill, construction of LFG collection wells, LFG extraction and LFG Flaring.

2) Phase-2-Implementation of LFG purification to enriched Natural gas to utilise it as CNG based upon techno economic feasibility study based on actual LFG Quality and Quantity.

5.7.1 Phase-1 works:

The Phase -1 field work was started in August-2012 with a project schedule of 7 months involving the following activities:

1) Waste leveling& Slope reformation

2) Provision of Surface Liner (Geo-Membrane & Geo Textile cover)

3) Construction of LFG wells and Leachate recirculation system

4) Installation of LFG Collection Network

5) Installation of enclosed Flare System

6) Infrastructure Development

5.7.1.1 Waste leveling& Slope reformation:

The project area had non-uniform side slopes. Therefore engineered slopes with maximum steepness up to 1V:2H to 1V:3H was proposed with flat benches along the slope for stability purpose. The steep slope was maintained to reduce the earth work to avoid the escape of LFG & maximise the collection efficiency.

Slice A is the flat area with an average height of more than 30m and Slice B&C are steeper with height varying between 15-20 meters.

5.7.1.2 Provision of Surface Liner:

A cover layer was provided over the final finished profile of the fill (i.e. on the top and side slopes). The final cover for closure of landfill is composed of several layers, each with a specific function. Various components of the surface cover are designed to maximise surface drainage, minimize infiltration and erosion and control the release of the LFG:

1) Protective layer: A protective layer of 200 mm thick soil layer is provided along the reformed slope& top portion.

2) Impervious Layer: An impervious layer of 1.5 mm thick HDPE liner (Geo-membrane) was provided as a waterproof layer and to prevent the escape of LFG into the atmosphere. Further a 1.5 mm thick Geo- composite layer was provided to act as a drainage layer.

3) Top cover: The top layer was formed by 450mm thick soil layer & vegetative cover was provided over the area where the slope is 1:3.

Top liner in steep slopes: In the steep slopes top cover is provided by paver block in the area adjoining to the active landfill & in other areas grass paver block &Geo Cell with grass cover is provided as the top liner to provide stability to the steep slopes.

The sequence of laying of Surface Liners is indicated in the following pictures:

HDPE Laying

Laying of Top Soil (V egetation Layer)

Installation of Liner System with Plain Paver Blocks:

Laying of Plain Paver Block Plain Paver Block

Installation of Liner System with Installation of Grass Paver Blocks:

Laying of Grass Paver Blocks on Slope. Grass Paver Block installed. Laying of Grass Paver Blocks.

Installation of Grass Paver Block.

Installation of Liner System with Geo Cell:

Laying of Geogrid Laying Of Geo Cell

Tying Work of Geo Cell Soil Filling in GeoCell on Slope

5.7.1.3 Construction of LFG wells and Leachate re-circulation System :

The LFG pump test data indicated the radius of influence of each well as 25m, i.e. equal to 1.25 and 2.5 times its depth. Typically, tominimize gaps in collection system coverage, some degree of overlap in wells' radius of influence is also permitted. Accordingly, 20 No's of LFG wells were constructed in the earmarked area with maximum no. of wells in Slice-A. The bore diameter of wells is 500mm and drilled up to 75% of depth of waste in which HDPE pipe of 160mm, with bottom 2/3 slotted is inserted. The annular core between the HDPE pipe and extraction well are filled with gravels of 25-40 mm size. The top of the LFG well is sealed with Bentonite seal (1500mm in Length) and capped. Out of the 20 wells, 11 wells are dual wells and provided with Leachate pumps. The LFG well cross section is shown in Figure-4 :

The leachate extraction pumps are pneumatic type, capable of extracting the leachate from the same bore of LFG hole and each pump is capable of extracting minimum 7.5 litres per minute of leachate from the landfill.

Fig. 4. Cross section of LFG well

5.7.1.5 Installation of LFG Collection Network:

Gas collection network comprising of adequate number of inter-connected header and feeder HDPE pipes were provided for collection of LFG. The feeder pipe (110mm dia.) collects LFG from the well and transfers the same to the header pipe (200/160 mm dia.). The gas piping network was laid in trenches at a depth of approximately 30cm from the finished level of landfill. Suitable protection was provided to the gas collection network in those areas where vehicular movement is anticipated.

5.7.1.4 Installation of enclosed Flare System:

An enclosed Flare System with Blowers and associated Controls was designed with a residence time of greater than 0.3 seconds at 800-1000oC with a destruction efficiency of 99% with smokeless flame under steady state for lean burning of LFG with CH4 concentration as low as 25% (Scottish environment protection Agency, 2002). The flare stack height is 10 m. Controlled Automatic/Motorized air dampeners provide ambient air to the flare for combustion and for controlling exit gas temperature. The Ignition is auto controlled and initial pilot ignition is provided by LPG.A Deflagration type flame arrester is provided for preventing back flow. The pictorial illustration of Flare System Installation is provided below:

Erection of Gas Flare System Flare Sytem Instrumentation

Erection of Gas Flare System

Gas Flare System

5.7.1.6 Infrastructure Development

The project entailed construction of a Control Room for monitoring the activities during construction phase and O&M after commissioning. Associated infrastructure development viz. Approach Road, Street Lighting, Fencing etc. was also carried out as part of the Project.

5.8 LFG Operations:

The LFG collection and Flare system was commissioned in Apr-2013. The initial LFG flow rate &CH4 concentration during the trial run period (2nd& 3rd May, 2013) is indicated in Figure-5:

Fig. 5. Methane Quality & Quantity w.r.t. time

After the trial run, LFG plant was operated on continuous basis. The Flare was stabilised and steady state operating process parameters were established. The operating results of three months from May to July-13 were observed & the daily average LFG Flow rate, CH4 Concentration & yields are indicated in Figures 6 to 14:

Average LFG Flow Rate (m3/hr)

ISO I 300 E 2S0

ü 200 g

3 ISO ■

3 100 0

* 50 D

M-May 16May 18 May 20-May 22-May 2J-May 26-May 28-May 30-May L-Jun Date

Methane {Vol%)

30 25 20 IS 10

M-May 16-May 13-May 20-May 22-May 24-Mjy 26-May 28-May 30-May L-Jun Date

Fig. 6. Daily avg LFG Flowrate in May-13.

Fig. 7. Daily avg. CH, Vol% in May-13

Average Methane Yield (m3/hr)

3 75.00

> 55.00

l as.oo

£ 35.00

£ 25.00

Average Flow Rate (m3/hr)

« 100

16-May

21-May Dale

26-May

1-Jun 6-lun 11-Jun 16-Jun 21-Jun 26-Jun 1-Jul Dale

Fig. 8. Daily avgyield of CH, (m3/hr) in May-13.

Fig. 9. Daily avg LFG Flowrate in June-13.

Fig. 10. Daily avg CH, Vol% in June-13.

Fig. 11. Daily avg Yield of CH, (m3/hr) in June-13

Fig. 12. Daily avg Flowrate of LFG in July-13.

Fig. 13. Daily avg CH, Vol% in July-13.

Average Methane Yield (cum/hr)

I 550 s\ A

| 20.0 ■ ^^ 15.0

1-Jul 6-Jul 11-Jul 16-Jul 21-Jul 26-Jul 31-Jul

Fig. 14. Daily avg Yield of CH, (m3/hr) in July-13.

5.9 Results Analysis:

On careful analysis of LFG operations, it is observed that the average LFG Flow rate has stabilised at 130 m3/Hrwith CH4 concentration of 28%. It is further observed that the CH4 concentration falls with increasing LFG Flow rate and comes down to 15% at a Flow rate of more than 350 m3/hr, leading to tripping of flare. Itis also observed that at a reduced LFG flowrate of 80-100 m3/Hr the CH4 concentration goes above 35%.

The average yield of CH4from LFG is dependent on Flow rate and composition (which are inversely related) and comes to about 30-40 m3/hr.Further, it is observed that the LFG flowrate, CH4 Concentration & Yield have considerably reduced from the trial period indicating that the Landfill site is in matured stage &the yield could further drop in future based on FODPrinciple. The LFG flow rate is less than the rate predicted through Pump Test and Modeling.The following could be the reasons for the reduced flow rates, compared to the estimates :

a) The sample Pump tests were conducted on a small area of the landfill site with 3 no.s of wells.

b) LFG generation from landfill is the result of interplay between total quantity of organic material buried in the landfill, moisture content, compaction techniques, temperature, waste type and particle size etc. In addition, lot of Construction & Demolition (C&D) material is dumped in the Landfillswhich cannot be predicted (a lot of C&D wastes were encountered during well construction in slices B & C of the Pilot project).

It was observed that the three Slices taken for study (Slice A, B &C) showed marked variation in the LFG generation potential. This may be on account of different composition and age of waste buried in thesethree Slices. The average flow rate obtained from Slice A is much higher than that obtained from Slice B and C under similar suction pressure level. The volumetric flow rate from slice A is 80-90 % of the total flow rate obtained from the Project area. This indicates that Slice A is having the right combination of waste and is capable of generating sustainable LFG flow with CH4composition in the range of 35- 40%. However, slice B and C could not give the desired output, which may be on account of variation in the type of waste dumped in this area and also their location, which is on the outer edge of the Ghazipur landfill. d) As the Landfill site was not covered & compacted at the right time would have led to early escape of LFG to atmosphere. It was also observed that the O2 content in the LFG remained consistentlybelow 2% eventhough part of closed landfill is in continuation with active landfill. This was possible due to proper design &construction to minimize the influence of the active landfill site. The N2 content varied between 2-15% and observed H2S concentation is well below 15ppm.Thus the Design and Operation of Landfill was managed well and did not allow ingress of air from adjoining active landfill site.

5.10 Phases-2 Implementation:

From the results it can be in freed that the actual LFG quality and quantity encountered in the pilot plant site is hugely in variant with the estimates. Indeed, utilization of this low quality LFG is a challenging task. As a pioneer of Natural Gas economy in India, GAIL is initially interested in upgrading of this LFG to Natural gas quality and uses it as a transportation fuel in the form of CNG . In this direction, GAIL has carried out in -house quick feasibility study based on various LFG purification technologies like Vacuum PSA system , Amine absorption system, Membrane system and water scrubbing system (IEA,2000). Even though PSA system was found suitable for the present conditions, the cost economics associated with the same is highly prohibitive due to the requirement of multiple trains for achieving the required purification. Hence the plan to covert low quality LFG to CNG was kept in abeyance and meanwhile alternate utilization for LFG is explored.

5.11 Generating Power From Low Quality LFG Using Microturbine:

It is evident that this low quality LFG with approximately 25 percent methane content, contains approximately one fourth of the energy of natural gas and this makes it still an attractive fuel for generation of power. There are several methods / technologies for generation of power from normal LFG which contains nearly 50-60% of methane. The most common is to use a gas engine/generator unit and produce electricity from LFG and the same is widely practiced in European countries (Roe, 1998).

For the present case, after evaluations of various power generating technologies, Micro-Turbine based technology has been selected for demonstration purpose. Micro-Turbines have the operation principle based on Brayton open cycle as depicted in the following Figure 15 with recuperations arrangement to partially recover the exhaust heat and this allows the net cycle efficiency to be increased to as much as 30%. But with a CHP arrangement the efficiency can be improved more than 80% (Bove and Lunghi, 2006).

Fig. 15.Flow Scheme of Recuperated MicroturbineBrayton Cycle

Micro-Turbine is compact, highly thermal efficient and flexible in operations coupled with its high reliability and minimum moving parts with enhanced equipment life and less maintenance cost is a suitable technology for the instant case.

Considering the current flow rate of 100-150 m3/hr of LFG, initially it is planned to install a 30KW capacity

micro turbine at the Landfill site, which shall utilise 60-70m3/hr of LFG. As a minimum of 30% of Methane concentration is required at the inlet of Micro-Turbine, a high pressure water scrubbing system shall be used to partially upgrade the LFG quality to meet these requirements.

A lot of challenges are involved in partial up gradation of LFG and its integration with Micro Turbine for power generation and this is being tried for the first time in India. On successful implementation of this kind of project, it shall showcase utilization of LFG, extracted from un-scientifically managed landfills, as a renewable source for power generation.

6. Discussions:

The project The Pilot LFG plant was installed on an active Landfill site: first of its kind in India. Average LFG Flow rate stabilised at 125-130 m3/hr& CH4 concentration stabilised at 25 %(Vol).Although the project boundary was contiguous with the active landfill, the O2 ingress in the LFG was minimal due to good Design and work quality.(Average O2 concentration in LFG is <2%(Vol.) & H2S is <15 ppm.). Further the Project was also successfully Validated & Registered with UNFCCC for availing CDM benefits. So far, ~10000MT of CO2 Equivalent of Methane is Captured and destroyed leading to accrual of ~10000 CERs.

More over based upon our experiences during the implementation of LFG Pilot Project, it is felt the following conditions and factors has to be suitably addressed, so that this kind of projects are replicated easily and their economics can be improved of

1) By carrying out the project in a more scientifically managed landfill site ii) Recovery of LFG has to be initiated within 2-3 years of waste dumping to improve the recovery potential.

2) Carrying out at the Landfill which have sufficient organic waste >50%

3) Carry out this kind of project on a Landfill which is of sufficient height (over 20m) with an area more than 10 Hectares, with Compaction and soil covering carried out at earlier stage itself on a Cell to Cell basis to prevent release of LFG to atmosphere.

4) Promoting of source segregations of waste as lot of Concrete & Construction demolishing waste also entering the Landfill site.

5) Local communities also co-opted as a stake holder for this kind of project so that LFG can be directly used a domestic fuel by the communities.

Regarding economic use of LFG, the same can be used to generate Power or can be upgraded to Pipeline quality natural gas for use as PNG / CNG. LFG contains various impurities like CO2, H2S etc. besides toxic compounds like Arsenic, Siloxanes etc. Turbines are available that can directly use the LFG as Fuel for generating power. Regarding its use as PNG/CNG, the gas needs to be purified to meet the stringent standards. It is known that technologies are available for such purification treatment but the cost and viability needs to be ensured. Alternatively, the option of directly using LFG as a domestic fuel in nearby areas could be explored after removing moisture and carrying out minimum purification without the need for mixing in the main natural gas pipeline.

7. Conclusion:

The huge quantity of MSWgenerated in India offers a good potential for collection and utilization of LFG butits economic utilisation is a serious challenge. The whole gamut of MSW management system is un-planned as it starts with mixing of organic waste with inerts at the source level itself and finally leading to dumping at landfill sites with about 40% C&D material. The landfill sites do not have any system for segreagtion w.r.t. age of MSW nor are they covered on time to prevent LFG escape. The LFG upgradation may also pose challenges due to presence of toxic compounds like Arsenic, Siloxane etc. Lastly, there are no government incentives in this endeavour.

Eventhough utilization of LFG may not be viable in the near term, but its collection and flaring should be practiced as it is safe and helps destructs Methane, a GHG 25 times more potent than CO2 (Incidentally, the CO2 present in LFG is not considered as a GHG but considered to be biogenic, and therefore a natural part of the carbon cycle) and thereby reduces Global Warming. This shall not only generate carbon credits but also improve the aesthetics of the landfill sites thereby improving the quality of life of people living neaby. These Projects shall also help strengthen India's Case on CO2 emissions target setting at the World Forums on Climate Change.

References:

1) Bove, R., &Lunghi, P. (2006). Electric power generation from landfill gas using traditional and innovative technologies. Energy Conversion and Management, 47(11), 1391-1401.

2) Detailed feasibility & Project Report for Ghazipur Pilot Project (2010). GAIL (India) Ltd, New Delhi.

3) Farquar, G. H., and F. A. Rovers. Gas Production during Refuse Decomposition. (1973). Water, Air & Soil Pollution 2 (4) December.

4) Guidance on Landfill gas flaring(2002).Scottish environment protection Agency, Edinburg.

5) González, C., Buenrostro, O., Marquez, L., Hernández, C., Moreno, E., & Robles, F. (2011). Effect of solid wastes composition and confinement time on methane production in a dump. Journal of Environmental Protection, 2(10), 1310-1316.

6) International Energy Agency (IEA). 2009. "Turning a Liability into an Asset: The Importance of Policy in Fostering Landfill Gas Use Worldwide." Paris, France. Retrieved from the Environmental Protection Agency website www.iea.org/textbase/papers/2009/ landfill.pdf.

7) International Energy Agency IEA (2000). Bioenergy Task 24: energy from biological conversion of organic waste. Biogas upgrading and utilization. International Energy Agency

8) Kjeldsen, P., Barlaz, M. A., Rooker, A. P., Baun, A., Ledin, A., & Christensen, T. H. (2002). Present and long-term composition of MSW landfill leachate: a review. Critical reviews in environmental science and technology, 32(4), 297-336.

9) Ramani, T., Sprague, S., Zietsman, J., Kumar, S., Kumar, R., & Krishnan, A. (2011). Landfill gas to energy applications in India: prefeasibility analysis of Mumbai landfills. Journal of Hazardous, Toxic, and Radioactive Waste, 16(3), 250-257.

10) Roe, S. M. (1998). Emerging technologies for the management and utilization of landfill gas. US Environmental Protection Agency, National Risk Management Research Laboratory.

11) Siddiqui, F. Z., Zaidi, S., Pandey, S., & Khan, M. E. (2013). Review of past research and proposed action plan for landfill gas-to-energy applications in India. Waste Management & Research, 31(1), 3-22.

12) U.S. Environmental Protection Agency (EPA). (2009). LFG Energy Project Development Handbook. Retrieved from the Environmental Protection Agency website http://epa.gov/lmop/res/handbook.htm.