1

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: zietsman@tamu.edu 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: b-gokhale@ttimail.tamu.edu 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: d-lord@tamu.edu 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: M-Bari@ttimail.tamu.edu 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: a-rand@ttimail.tamu.edu 42 43 * Corresponding author 44 45

46

2

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

5

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

6

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

7

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

8

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

9

• 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

11

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

13

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

14

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.

15

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.

16

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