1 Feasibility of Landfill Gas as a Liquefied Natural Gas Fuel 2 … · 2008. 2. 19. · 1 1...
Transcript of 1 Feasibility of Landfill Gas as a Liquefied Natural Gas Fuel 2 … · 2008. 2. 19. · 1 1...
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Feasibility of Landfill Gas as a Liquefied Natural Gas Fuel 1
Source for Refuse Trucks 2 3 Paper # 489 4 5 Josias Zietsman, Ph.D., P.E.* 6 Director, Center for Air Quality Studies 7 Texas Transportation Institute 8 The Texas A&M University System 9 College Station, TX 77843 10 (979) 458-3476 (voice) 11 E-mail: [email protected] 12 13 Bhushan Gokhale 14 Jacobs Engineering Group Inc. 15 6688 N. Central Expressway 16 Dallas, TX 75206-3914 U.S.A. 17 Phone: (214) 424-7500 (voice) 18 E-mail: [email protected] 19 20 Dominique Lord, Ph.D., P.Eng. 21 Assistant Professor 22 Texas A&M University 23 College Station, TX 77843 24 979-458-3949 (voice) 25 E-mail: [email protected] 26 27 Ehsanul Bari 28 Graduate Research Assistant 29 Center for Air Quality Studies 30 Texas Transportation Institute 31 College Station, TX 77843 32 (979) 595-3305 (voice) 33 E-mail: [email protected] 34 35 Aaron J. Rand 36 Research Associate 37 Center for Air Quality Studies 38 Texas Transportation Institute 39 College Station, TX 77843 40 (979) 595-3305 (voice) 41 E-mail: [email protected] 42 43 * Corresponding author 44 45
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ABSTRACT 47
48
The purpose of this paper is to develop a methodology to evaluate the feasibility of using landfill 49
gas (LFG) as a Liquefied Natural Gas (LNG) fuel source for heavy-duty refuse trucks operating 50
on landfills. Using LFG as a vehicle fuel can make the landfills more self-sustaining, reduce their 51
dependence on fossil fuels, and reduce emissions and greenhouse gases. Acrion Technologies 52
Inc. in association with Mack Trucks Inc. developed a technology to generate LNG from LFG 53
using the CO2 WASH™ Process. A successful application of this process was performed at the 54
Eco Complex in Burlington County, PA. During this application two LNG refuse trucks were 55
operated for 600 hours each using LNG produced from gases from the landfill. 56
57
The methodology developed in this paper can evaluate the feasibility of three landfill gas options 58
– do nothing, electricity generation, and producing LNG to fuel refuse trucks. The methodology 59
involved the modeling of several components – landfill gas generation, energy recovery 60
processes, fleet operations, economic feasibility, and decision-making. The economic feasibility 61
considers factors such as capital costs, maintenance costs, operational costs, fuel costs, emissions 62
benefits, tax benefits, and the sale of products such as surplus LNG and food grade carbon 63
dioxide (CO2). 64
65
Texas was used as a case study. The 96 landfills in Texas were prioritized and 17 landfills were 66
identified that showed potential for converting LFG to LNG for use as a refuse truck fuel. The 67
methodology was applied to a pilot landfill in El Paso, TX. The analysis showed that converting 68
LFG to LNG to fuel refuse trucks proved to be the most feasible option and that the methodology 69
can be applied for any landfill that considers this option. 70
71
IMPLICATIONS STATEMENT 72
73
This manuscript demonstrates that it is possible and potentially feasible to convert LFG to LNG 74
to fuel refuse trucks. Practical implications could include for cities to develop LFG-to-LNG 75
conversion plants and to acquire and operate LNG-fueled vehicles as opposed to diesel-fueled 76
3
vehicles. Finally, this approach can provide nonattainment areas with another medhod to reach 77
attainment and meet conformity standards. 78
INTRODUCTION 79
80 Energy consumption throughout the world has increased substantially over the past few years 81
and the trend is projected to continue well into the future. The primary sources of energy are 82
conventional fuels such as oil, natural gas, and coal. The most apparent negative impacts of these 83
conventional fuels are global warming, poor air-quality, and adverse health effects. Considering 84
these negative impacts, it is necessary to develop and use non-conventional sources of energy. 85
LFG generated at landfills can serve as a non-conventional source of energy if cleaned of certain 86
impurities and additionally as a transportation fuel if it is adequately cleaned. This fuel can then 87
be used as a fuel source for the refuse trucks operating at landfills. The refuse trucks primarily 88
operate in the residential and commercial areas and any fuel consumption and emissions 89
improvements will have considerable positive environmental benefits for the community. 90
91
Mack Trucks Inc. in association with Acrion Technologies Inc have demonstrated that methane 92
produced by landfills can be converted to commercial level LNG and can consequently be used 93
as a fuel for refuse trucks. This is achieved through their CO2 WASH™ process, which is a 94
sophisticated chemical process that separates the CO2 and oxygen (O2) from methane providing 95
clean landfill gas with a high methane content that can be liquefied to produce LNG for use as 96
vehicle fuel. The process was demonstrated during a very successful application at the Eco 97
Complex in Burlington County, NJ. During this application, two refuse trucks fueled with LNG 98
produced by the landfill were tested for more than 600 hours and produced exceptional 99
performance, maintenance, and fuel consumption results. This was the first application of this 100
magnitude and it was shown that the process is transferable to other landfills. 101
102
Using the LFG for vehicular fuel applications has been much more recent as compared to other 103
applications such as electricity and heating.1, 2 There are, therefore, very limited studies on the 104
economic feasibility of this option and the possible environmental benefits. 105
106
4
The purpose of this paper is to develop a methodology to evaluate the feasibility of using LFG as 107
an LNG fuel source for heavy-duty refuse trucks operating at the landfill. The methodology 108
developed in this paper can evaluate the feasibility of three landfill gas options – do nothing, 109
electricity generation, and producing LNG to fuel refuse trucks. The methodology involved the 110
modeling of several components – LFG generation, energy recovery processes, fleet operations, 111
economic feasibility, and decisions making. The economic feasibility considers factors such as 112
capital costs, maintenance costs, operational costs, emissions benefits, and sale of any products. 113
Texas was used as a case study. The 96 landfills in Texas were prioritized and 17 landfills were 114
identified that showed potential for converting LFG to LNG. The methodology was applied to a 115
pilot landfill in El Paso, TX. 116
117
The paper is divided into the following four sections — introduction, overall approach, Texas 118
case study, and concluding remarks. 119
120
OVERALL APPROACH 121
122
The overall approach involves the modeling of six distinct components that provide the city or 123
landfill owner with enough information to make a decision whether to convert LFG to LNG to 124
fuel refuse trucks. The approach was coded into a user-friendly analysis tool that can be used by 125
cities and landfill owners to perform their own analyses. Figure 1 shows a flow chart of the 126
analysis process. This figure shows that the process begins with the generation of the LFG. The 127
gas may then be used in one of three ways – do nothing (flare), generate electricity, or produce 128
transportation fuel. 129
130
If transportation fuel is produced, it will be necessary to have a replacement scheme where 131
diesel-fueled trucks are replaced by LNG-fueled trucks over time. Regardless of the method, the 132
refuse trucks will continue to operate, burn fuel, and produce emissions. All the costs and 133
benefits associated with these options will be calculated to evaluate the relative economic 134
feasibilities. This can lead to a decision or a repeat of the process while performing sensitivity 135
analyses. The following sections describe each of the steps in more detail. 136
137
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LFG Generation 138
139
LFG is primarily composed of methane (CH4) and CO2 along with some quantities of nitrogen 140
(N2) and O2. A few trace compounds may also be found in the LFG.3 The composition of the gas 141
depends upon various factors such as the type of waste in a landfill, climatic conditions at the 142
landfill, and age of the landfill among others. The composition of the gas may also vary by 143
location within the landfill, i.e., if it is collected at the center or at the periphery.4 Table 1 144
presents a typical composition of LFG. 145
146
There are several models that can be used to estimate the amount of LFG generated at landfills. 147
The accuracy of the estimates depends upon the type of model used and the underlying data used 148
in the models. Equation 1 shows the model used to estimate the amount of LFG generated due to 149
the incremental waste acceptance ratio (WAR) at the landfill.5 150
151 )(
0lttkekLOCWLFG −−××××= (1) 152
153
Where, 154
LFG = annual LFG generation rate, cf/year; 155
W = waste acceptance rate, tons; 156
L0 = CH4 generation potential, cf of CH4 per ton of waste; 157
k = rate of decay, yearly; 158
t = time after waste placement, years; 159
tl = lag time, years; and 160
OC = organic content, percentage. 161
162
This model requires information on the waste acceptance ratio at a landfill as well as additional 163
parameters such as rate of decay of the municipal solid waste, CH4 generation potential of the 164
MSW, lag time, and time after placement. Lag time refers to the time difference between 165
placement of MSW at a landfill and generation of the LFG. It should be noted that for this 166
modeling purpose, the lag time was assumed to be zero.5 The values of (L0) and (k) are 167
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dependent upon the amount of rainfall and presence of a leachate re-circulation system at the 168
landfill. 169
170
Energy Recovery Processes 171
U.S. landfills are responsible for a third of all methane emissions worldwide and methane is 21 172
times more powerful than CO2 at warming the atmosphere. Depending on the amount of methane 173
produced, U.S. Environmental Protection Agency (EPA) regulations require that the gas be 174
allowed to escape into the atmosphere or has to be sucked out and burned, or captured in another 175
way.6 176
177
Landfill gas is extracted from landfills using a series of wells and a blower/flare (or vacuum) 178
system. This system directs the collected gas to a central point where it can be processed and 179
treated depending upon the ultimate use for the gas. From this point, the gas can be simply flared 180
or used to generate electricity, replace fossil fuels in industrial and manufacturing operations, 181
fuel greenhouse operations, upgraded to pipeline quality gas, or developed into transportation 182
fuel. 183
184
The most basic and least productive way of disposing of methane is to burn it in a flare. The 185
other productive uses of the LFG require some of the components of the LFG to be removed, 186
which is referred to as cleaning. The degree of cleaning depends on the intended application of 187
the LFG.3,7 Each type of energy recovery project therefore, has a unique requirement for 188
processing the gas. The LFG typically has heating values that range between 450-to-600 British 189
thermal units (Btu) per standard cubic foot and is mostly saturated with water.1 The various 190
medium-to-high Btu applications of the gas demand removal of moisture from the gas and the 191
cost of such preprocessing is high and could have a significant impact on the overall economic 192
feasibility of the project.7 193
194
Electricity Generation 195
Generating electricity from LFG comprises about two-thirds of the current operational projects in 196
the U.S. Electricity for on-site use or sale to the grid can be generated using a variety of different 197
technologies — internal combustion engines, turbines, microturbines, Stirling engines (external 198
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combustion engines), Organic Rankine Cycle engines, and fuel cells. The vast majority of 199
projects use internal combustion engines or turbines, with microturbine technology being used at 200
smaller landfills and in niche applications. Certain technologies such as the Stirling and Organic 201
Rankine Cycle engines and fuel cells are still in the development phase.6 202
203
Vehicle Fuel Production 204
The CO2 WASH™ process is capable of effectively cleaning LFG so that it can be used as a fuel 205
for refuse trucks. Figure 2 shows a diagram describing the CO2 WASH™ process. In simple 206
terms, this process begins by the removal of unwanted substances such as hydrogen sulfide (H2S) 207
and water vapor. Refrigeration then separates the gas into methane and food grade CO2. The 208
volatile organic compounds are burned in a flare. The contaminant free methane can then be 209
taken through the liquefaction process to produce adequately cleaned LNG that can be used as 210
transportation fuel. 211
212
The capture rate at landfills is approximately 80% of raw LFG.8 As shown in Table 1, 213
approximately 50% of this raw LFG is composed of methane. A sophisticated process such as 214
the CO2 WASH™ process can convert approximately 80% of this methane to LNG. 215
Approximately 10,000 gallons of LNG can, therefore, be produced per day for every 2 million 216
cubic feet of LFG.9 217
218
Fleet Conversion 219
The typical price of a new diesel-fueled refuse truck is more than $100,000 and LNG-fueled 220
refuse trucks cost approximately $30,000 more. However, with the help of a tax credit the 221
difference is reduced. It is still not conceivable that a landfill will replace all their existing diesel-222
fueled trucks with LNG-fueled trucks at one time. Instead, it will follow some replacement 223
scheme over time. In addition, the average retirement age of refuse trucks is seven years 224
resulting in another opportunity for replacements of existing diesel-fueled trucks with LNG-225
fueled trucks. The analysis tool developed under this project makes it possible for the landfill 226
owner to evaluate the feasibility of various replacement schemes. 227
228
229
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Fleet Operations 230
Refuse trucks have unique operating characteristics because they have to start and stop at very 231
short distances for collecting waste from several disposal bins. This results in numerous 232
accelerations, decelerations, and idling at short intervals. The refuse trucks also have to travel on 233
the highway system to and from the landfill, which involves high-speed cruising. Other 234
important characteristics typical of refuse truck operations are the varying loads carried by such 235
trucks and hydraulic compactions performed by some types. 236
237
The operating characteristics of refuse trucks are best described with drive cycles, which are 238
speed profiles used to replicate the driving pattern of a vehicle. It is normally developed as the 239
speed of a vehicle as a function of time or distance and includes operating characteristics such as 240
acceleration, deceleration, idling, creep idling, and cruising. One purpose of developing a drive 241
cycle is to replicate the driving conditions during emissions and fuel consumption testing and 242
modeling. 243
244
Refuse trucks operating at the Clint Landfill in El Paso were equipped with Global Positioning 245
System (GPS) units to collect their second-by-second position data. The GPS units consist of a 246
GPS receiver/antenna and a GPS data logger. The GPS data was then used to develop drive 247
cycles for each of the four modes of operation – urban driving, trash collection, freeway driving, 248
and landfill operations. Figure 3 shows sample speed profiles for the four operational modes. A 249
detailed description of the drive cycles and their development can be found elsewhere.10 250
251
Economic Feasibility 252 The economic feasibility model considers the feasibility of the three options – do nothing (flare 253
the LFG), electricity generation, and converting LFG to LNG to fuel refuse trucks. The net 254
present worth (NPV) technique was used for this purpose to facilitate the decision-making. The 255
following factors were included in the economic analysis model: 256
• capital cost of conversion equipment (electricity generation or vehicle fuel); 257
• maintenance and operational cost of conversion equipment (electricity generation or 258
vehicle fuel); 259
• capital cost of truck fleet conversion (diesel and/or LNG); 260
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• maintenance and operational cost of truck fleet (diesel and/or LNG); 261
• emissions benefits; 262
• tax credits; and 263
• sale of products – electricity, food grade CO2, and surplus LNG. 264
265
Values for the capital, maintenance, and operational costs of the conversion equipment were 266
obtained from existing owners and operators of these facilities. Similarly, values for the capital, 267
maintenance, and operational costs of refuse trucks were obtained from landfill operators. The 268
difference in costs between LNG and conventional diesel-fueled trucks were obtained from 269
various literature sources. Similarly, tax credits for the production of electricity from landfills 270
and the production of LNG from landfills as well as sale prices for products such as electricity, 271
food grade CO2, and surplus LNG were obtained from the literature. 272
273
Developing values for emissions and associated emissions benefits involved a comprehensive 274
process. The Texas Transportation Institute used portable emissions measurement system 275
(PEMS) equipment to measure the emissions and fuel consumption of three diesel-fueled refuse 276
trucks during actual operating conditions at the El Paso landfill. Rates from the MOBILE6 277
emissions model were used to augment the measured rates to make them cover a broad range of 278
model years and refuse truck types. Emissions and fuel consumption differences between diesel-279
fueled and LNG-fueled refuse trucks were obtained from previous studies. The emissions and 280
fuel consumption could then be determined for each trip based on the rates for that truck type 281
(diesel or LNG fueled), model year, and distance traveled in each component of the drive cycle 282
(urban driving, trash collection, freeway driving, and landfill operations). Costs are then 283
associated with the different pollutants – NOx ($13,000/ton), HC ($10,700/ton), CO 284
($15,600/ton), CO2 ($42/ton), and PM ($26,000/ton).11, 12, 13 285
286
Decision Making 287
All the aspects and equations associated with the economic feasibility analysis were coded into a 288
user-friendly analysis tool. A landfill owner or city using the tool will be prompted to enter the 289
required input data and the tool will then perform all the required calculations. All the costs and 290
benefits associated with these options are calculated over a 20-year analysis period and brought 291
10
to current year dollars using the NPV method allowing comparison of the various options. Each 292
round of analysis can lead to a decision or a repeat of the process while changing parameters as 293
part of sensitivity analyses. 294
295
TEXAS CASE STUDY 296 297
Inventory of Landfills in Texas 298
The first step was to develop an inventory of Texas landfills that includes information on the 299
landfill name, location, ownership, amount and classification of waste in place (WIP), size and 300
depth, presence of LFG collection system, and amount of LFG collected. It also includes details 301
about the operational status of energy recovery projects at the landfill and the amount of LFG 302
consumed by such projects. EPA’s Landfill Methane Outreach Program (LMOP) database 303
contains information on 2,456 landfills nationwide with 96 being in Texas.3 This database 304
provided good information and was supplemented by interviews of key people at individual 305
landfills. The 96 landfills in Texas were short-listed using the evaluation criteria based on those 306
developed by the EPA with regards to WIP, waste acceptance, depth, and gas generation rate.14 307
308
It was found that 17 landfills in Texas have the potential for energy recovery projects including 309
the production of LNG to fuel their refuse trucks. Figure 4 shows a map of the eight-hour ozone 310
nonattainment and near nonattainment areas in Texas as well as the locations of the 17 short-311
listed landfill sites. The figure shows that nine landfills are located in nonattainment areas and 312
seven landfills are located in near nonattainment areas for ozone. Emissions saved due to 313
conversion of LFG to LNG could therefore, improve the attainment status of these areas. 314
315 Inventory of Refuse Trucks in Texas 316
Typically, there are two types of collection operations associated with refuse trucks — 317
residential and commercial. However, large cities may have a third type of collection operation 318
involving Citizen Collection Stations (CCS). The CCSs are selected sites where voluntary 319
disposal of waste is permitted. These sites are suitable for large commercial or bulk residential 320
disposal. The different types of collection operations require different types of refuse trucks. 321
These trucks have slightly different operational characteristics and include side loaders, front 322
loaders, rear loaders, and roll off compactors. 323
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324 The inventory of refuse trucks at the major landfills in Texas was assembled through a survey. 325
The survey was designed to collect information on truck fleet details and operational 326
characteristics. The survey was sent to the major refuse truck companies operating on the short-327
listed landfills in Texas. Information collected included the make and model year of the trucks 328
and the type and size of the engines. It also included information on the operational 329
characteristics of refuse trucks such as the type of collection operation, average round-trip length 330
to the landfill and number of trips to the landfill or transfer station. This information provided the 331
basis for modeling fleet and operational characteristics. 332
333
Example Application 334
The Clint Landfill located in El Paso was used as case study for this research. It is a large landfill 335
(one of the 17 short-listed landfills in Texas) with WIP of approximately 5 million tons and 336
annual WAR of 390,000 tons. The landfill is considered fairly typical and El Paso is considered a 337
medium-size Texas city.15 338
339
Table 3 shows the input data for the example application. The table shows that with a modest 340
amount of input data the full analysis can be performed. In addition to the input data listed in this 341
table, the user also has the ability to change the values of several other parameters such as the 342
cost of diesel, selling price of LNG, and the cost of emissions to reflect more current information 343
or to be able to perform sensitivity analyses. 344
345
Figure 5 shows the findings from the analysis by comparing the NPV of the three options – do 346
nothing (flare the LFG), establish a plant to generate electricity, and establish a plant to convert 347
the LFG to fuel refuse trucks. It should be noted that the NPV values are negative because it 348
costs money to own and operate a landfill and the values are therefore shown in the form of net 349
present costs (NPC) with the lowest NPC value indicating the most economically feasible option. 350
351
Figure 5 shows that the option of converting LFG to LNG is the most economically feasible 352
option (40% improvement over status quo) followed by converting LFG to electricity (18% 353
improvement over status quo). Note that the analysis performed is an economic evaluation and 354
12
not a pure financial analysis. In the case of a financial analysis the benefits due to emission 355
reductions would not be included because it is then based on pure cash flow. Additionally note 356
that the analysis is for illustration purposes and, based on other assumptions, the results would be 357
different. 358 359 Sensitivity analyses were performed by changing aspects such as the fleet growth rate, length of 360
the analysis period, cost of diesel, and selling price of LNG. The sensitivity analyses indicate the 361
variations in the NPV due to changes in the above factors and assist in developing better 362
decisions. For illustration purposes, Figure 6 shows the variation in NPC with regard to the cost 363
of diesel. The figure shows that, for all the cases, the NPCs increase linearly with increased price 364
of diesel. In addition, because the LFG-to-LNG option has a growing portion of the fleet 365
operating on LNG instead of diesel, the rate of increase in the cost for this option is less than that 366
of the other two options. This reduced impact due to diesel price increases makes the LFG-to-367
LNG option even more attractive. 368
369
This figure only assumes a variation in one of the factors and is for illustration purposes only. 370
More complex analyses, varying multiple factors in combination with one another, will improve 371
the final decision. The analysis tool provides for this flexibility and ease of use. 372
373 374
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CONCLUSIONS 375
376
The following could be concluded from this research project. 377
378
• There are several applications of LFG such as up-gradation to pipeline quality gas, 379
generation of electricity, use in fuel cells, and vehicular fuel. This study focused on the 380
conversion of LFG to vehicular fuel and compared it to the generation of electricity and 381
purely flaring the gas. 382
383
• The utilization of LFG for vehicular fuel applications is more recent than other 384
applications. Several tests have been performed by Mack Trucks, Inc. and Acrion 385
Technologies, Inc. to evaluate the feasibility of using LNG obtained from the LFG to fuel 386
refuse trucks and the results have been very promising. 387
388
• The application of LFG depends upon its quantity, composition, and quality. Researchers 389
identified 17 landfills in Texas that could potentially benefit from a LFG-to-LNG 390
conversion project to produce fuel for its refuse trucks. 391
392
• A methodology was developed that is based on the modeling of several components – 393
LFG generation, energy recovery processes, fleet operations, economic feasibility, and 394
decision-making. This methodology was coded into a user-friendly analysis tool and 395
applied to a pilot landfill in El Paso, TX. 396
397
• The preliminary results indicate that the methodology could easily be applied to landfills 398
and that the conversion of LFG to LNG proved to be the most economically feasible 399
option for the case study. It should be noted, however, that the analysis was for 400
illustration purposes and, depending on the values of several assumptions, the results 401
could be different. 402
403
404
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ACKNOWLEDGEMENTS 405
406 This paper was based on research performed for the State Energy Conservation Office (SECO). 407
The authors would like to thank Mary-Jo Rowan of SECO for her guidance and support during 408
the project. The authors would also like to thank Dr. Bruce Smackey of Mack Trucks Inc. for 409
providing technical support during the project. The authors would also like to thank Dr. 410
Mohamadreza Farzaneh of TTI for his contributions in the emissions data collection and drive-411
cycle development. Finally, the authors would like to thank Ellen Smyth and her staff of the City 412
of El Paso for their support and making their refuse trucks available for testing and providing 413
detailed data. 414
415
The opinions expressed in this paper reflect the views of the authors only and do not necessarily 416
reflect the points of view of any other sponsoring or contributing individual or agency. 417
418
REFERENCES 419
1. Siuru, W. D. Trucks: Taking LNG to the Streets. Waste Age. Aug. 1, 2000.
http://wasteage.com/mag/waste_trucks_taking_lng/, accessed January, 2008.
2. Cook, J. W., W. R. Brown, L. Siwajek, M. Neyman, T. Repert, and B. M. Smackey.
Production of Liquid Methane truck fuel from Landfill Gas – Final Report. Acrion
Technologies Inc. and Mack Trucks Inc., June. 2005.
3. Johns Hopkins University Applied Physics Laboratory, EMCON Associates, ESCOR, Inc.,
Argonne National Laboratory, Public Service Electric and Gas Company, Wehran Energy
Corporation, SCS Engineers, and The Brooklyn Gas Company. Landfill Methane Recovery.
Noyes Data Corporation, New Jersey, 1983.
4. Emcon Associates. Methane Generation and Recovery from Landfills. Ann Arbor Science
Publishers, Inc., Ann Arbor, MI, 1980.
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5. Augenstein, D., and SCS Engineers. Final Report Comparison of Models for Predicting
Landfill Methane Recovery. The Solid Waste Association of North America. March. 1997
6. Landfill Methane Outreach Program (LMOP). http://www.epa.gov/lmop/, accessed January,
2008.
7. Solid Wastes and Residues, Conversion by Advanced Thermal Processes. American
Chemical Society Symposium 76th Series. Washington, DC, 1978.
8. Landfill Gas Process. Engineered Gas Systems Worldwide.
http://www.enggas.com/Level_1/lfg_process.htm, accessed October. 20, 2005. 9. Waste Management’s LNG Truck Fleet: Final Results. Report NREL/BR-540-29073. U.S.
Department of Energy, National Renewable Energy Laboratory, January. 2001.
10. Zietsman, J., B. Gokhale, D. Lord, D. Lee, M. Farzaneh, and T. Jacobs. Application of
Landfill Gas as a Liquefied Natural Gas Fuel for Refuse Trucks in Texas. Draft Report for
State Energy Conservation Office. Texas Transportation Institute, the Texas A&M
University System, College Station, TX. October 2007.
11. Texas Emissions Reduction Plan: Guidelines for Emissions Reduction. Texas Commission on
Environmental Quality. http://www.tceq.state.tx.us/comm_exec/forms_pubs/pubs/rg/rg-
388.html, accessed January. 8, 2008.
12. Emission Reduction Credits Costs – California. Santa Barbara County Air Pollution Control
District. http://www.sbcapcd.org/eng/nsr/arb-data.htm, accessed April. 25, 2006.
13. Energy-Related Carbon Dioxide Emissions, International Energy Outlook 2006. U.S.
Department of Energy, Energy Information Administration.
http://www.eia.doe.gov/oiaf/ieo/emissions.html, accessed April. 25, 2006.
14. Turning a liability into an Asset: Landfill Gas to Energy Project Development Handbook.
U.S. Environmental Protection Agency, Landfill Methane Outreach Program, 1996.
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15. R.W. Beck, Inc. Solid Waste Management Department Financial and Operational Study –
Final Report. City of El Paso, TX. August. 2004.
420
ABOUT THE AUTHORS 421
422
Dr. Josias Zietsman is the Director of the Center for Air Quality Studies of the Texas 423
Transportation Institute (TTI). TTI is part of the Texas A&M University System. Bhushan 424
Gokhale is an employee of the Jacobs Engineer Group in Dallas, Texas. Dr. Dominique Lord is 425
an Assistant Professor at Texas A&M University. Mr. Ehsanul Bari is a Graduate Research 426
Assistant in the Center for Air Quality Studies at TTI and Mr. Aaron Rand is a Research 427
Associate in the Center for Air Quality Studies at TTI. 428
429
430
17
List of Tables 431
432
Table 1. Typical Composition of Landfill Gas. 433
Table 2. Inputs for El Paso Landfill. 434 435
18
Table 1. Typical Composition of Landfill Gas. 436
437 Component Percent (dry volume basis) Methane 47.5 Carbon dioxide 47.0 Nitrogen 3.7 Oxygen 0.8 Paraffin hydrocarbons 0.1 Aromatic and cyclic hydrocarbons 0.2 Hydrogen 0.1 Hydrogen Sulfide 0.01 Carbon monoxide 0.1 Trace compounds 0.5 Total 100
438 Table 2. Inputs for El Paso Landfill. 439 440
LANDFILL INPUTS
TRUCK FLEET INPUTS*
Current WIP (tons) 5 million Current Number of Trucks (per model
year bin) 110 Waste Acceptance
Rate (tons) 390,000
Bioreactor Landfill No Average Number of Stops 400
Amount of Rainfall (inches/month) 0.77
Distance per trip Urban, Freeway,
Collection, Landfill (miles)
4, 30, 5, 2
Organic Content (percentage) 32 Number of Trips to
Landfill per Day 2
Collection Efficiency
(percentage) N/A Collection Days
per Week 4
Raw LFG Consumption by other applications
(percentage)
N/A Annual
Replacements and Retirements
12 and 3
441 442
19
List of Figures 443
444
Figure 1. Flow Chart of Analysis Process 445
Figure 2. CO2 WASH™ Process 446
Figure 3. Sample Speed Profiles of Operation Modes 447
Figure 4. Location of Short-Listed Landfills and Nonattainment and Near Nonattainment Areas 448
in Texas 449
Figure 5. Net Present Cost Values of Various Options 450
Figure 6. Sensitivity Analysis with Variation of Diesel Price 451
452
453
20
454 Figure 1. Flow Chart of Analysis Process. 455
Landfill Gas
LNG
Electricity
Fleet Conversion
Flare
B1
C
B2
B3
Fleet Operation
End
A
F E
D
Economic Feasibility
Decision Iteration
21
456 Figure 2. CO2 WASH™ Process.457
LFG
Pretreatment Chamber
Compressor
H2S Removal
Dryer
CO2 WASH™ Chamber
Clean CO2
Gas Post treatmentMembrane Chamber
Liquefier
LNG Natural Gas
Flare
22
458 Figure 3. Sample Speed Profile of Operation Modes. 459
460
461 Figure 4. Location of Short-Listed Landfills and Nonattainment and Near Nonattainment Areas 462
in Texas. 463 464
23
465 Figure 5. Net Present Cost Values of Various Options. 466
467
468
Net Present Cost Values
$-
$50,000,000
$100,000,000
$150,000,000
$200,000,000
$250,000,000
Net
Pre
sent
Cos
t
Flare LFG LFG to Electricity
LFG to Transportation Fuel
24
469 Figure 6. Sensitivity Analysis with Variation of Diesel Price. 470
471
472
$100,000,000
$150,000,000
$200,000,000
$250,000,000
$300,000,000
$3.00
$3.20
$3.40
$3.60
$3.80
$4.00
$4.20
$4.40
$4.60
$4.80
$5.00
$5.20
$5.40
Price of Diesel per Gallon
Net
Pre
sent
Cos
t
Flare LFG LFG to Electricity LFG for Transportation Use