A NextSTEPS white paper by: Amy Myers Jaffe,1 Rosa Dominguez-Faus,1

Allen Lee,1 Kenneth Medlock,2 Nathan Parker,1 Daniel Scheitrum,1

Andrew Burke,1 Hengbing Zhao,1 Yueyue Fan1

NextSTEPS

(Sustainable Transportation Energy Pathways) Program

UC Davis Institute of Transportation Studies

February 18, 2015

Final Version

INSTITUTE OF TRANSPORTATION STUDIES

EXPLORING

the ROLE of

NATURAL GAS in

U.S. TRUCKING

1 Institute of Transportation Studies, UC Davis

2 Rice University
1

NextSTEPS White Paper:

Exploring the Role of Natural Gas in U.S. Trucking

Amy Myers Jaffe,

1 Rosa Dominguez-Faus,1 Allen Lee,1 Kenneth Medlock,2 Nathan 

Parker,1 Daniel Scheitrum,

1 Andrew Burke,1 Hengbing Zhao,1 Yueyue Fan1

1 Institute of Transportation Studies, UC Davis

2 Rice University

Abstract

The recent emergence of natural gas as an abundant, inexpensive fuel in the United 

States could prompt a momentous shift in the level of natural gas utilized in the 

transportation sector. The cost advantage of natural gas vis-à-vis diesel fuel is 

particularly appealing for vehicles with a high intensity of travel and thus fuel use. 

Natural gas is already a popular fuel for municipal and fleet vehicles such as transit 

buses and taxis. In this paper, we investigate the possibility that natural gas could be 

utilized to provide fuel cost savings, geographic supply diversity and environmental 

benefits for the heavy-duty trucking sector and whether it can enable a transition to 

lower carbon transport fuels. We find that a small, cost-effective intervention in 

markets could support a transition to a commercially sustainable natural gas heavyduty fueling system in the state of California and that this could also advance some 

of the state’s air quality goals. Our research shows that an initial advanced natural 

gas fueling system in California could facilitate the expansion to other U.S. states. 

Such a network would enable a faster transition to renewable natural gas or biogas 

and waste-to-energy pathways. Stricter efficiency standards for natural gas Class 8 

trucks and regulation of methane leakage along the natural gas supply chain would 

be necessary for natural gas to contribute substantially to California’s climate goals

as a trucking fuel. To date, industry has favored less expensive technologies that do 

not offer the highest level of environmental performance. 
2

Table of Contents

Abstract............................................................................................................................... 1

List of Figures..................................................................................................................... 3

List of Tables ...................................................................................................................... 4

Acknowledgements............................................................................................................. 5

Summary of Findings.......................................................................................................... 6

Background......................................................................................................................... 7

The U.S. and Global Natural Gas Vehicle Fleet............................................................. 8

Freight Supply Chain Competitiveness ........................................................................ 11

Energy Security through Geographic Diversification................................................... 11

Least Cost Options........................................................................................................ 12

High Traffic Density Routes: California’s Unique Characteristics.............................. 13

Barriers to Entry: High Capital Costs for New Infrastructure ...................................... 15

Carbon Intensity and Air Quality Considerations of Natural Gas in Transportation ... 16

The Case for Natural Gas: An Abundant, Domestic Fuel ............................................ 17

The U.S. Freight Supply Chain and Potential for Natural Gas..................................... 22

Barriers to Commercial Adoption of Natural Gas in Long-Distance Trucking............ 26

Vehicle cost............................................................................................................... 26

Cost of the refueling infrastructure ........................................................................... 28

Infrastructure Modeling Approach ............................................................................... 32

Modeling Results and Policy Analysis............................................................................. 33

Base case scenario......................................................................................................... 33

Alternative Scenarios.................................................................................................... 37

Alternative Scenario 1: U.S. Natural Gas Fueling Networks Under a Doubling of 

LNG Trucks.............................................................................................................. 38

Alternative Scenario 2: Subsidy Scenarios............................................................... 40

Alternative Scenario 3: High Oil Price Scenario ...................................................... 44

CNG as an Alternative to LNG Fuel............................................................................. 46

Business Models for Advancing Natural Gas in Transportation .................................. 48

Environmental Performance Analysis .......................................................................... 51

Particulate matter and Nitrogen Oxides.................................................................... 51

Greenhouse gases...................................................................................................... 55

Conclusions and Implications for Policy .......................................................................... 58
3

List of Figures

Figure 1. Annual Fuel Savings by Vehicle Miles Traveled.............................................. 10

Figure 2. Shale Resources in North America.................................................................... 18

Figure 3. Henry Hub Price, 2000-2030, according to Rice Model Status Quo Scenario 

(Real 2010$).............................................................................................................. 19

Figure 4. Estimated Expected Ultimate Recovery by Shale Play per Average Well by 

Location .................................................................................................................... 20

Figure 5. North American Shale Gas Resource and Average Breakeven Price by Play. . 21

Figure 6. Percent of New Class 8 Truck Sales with Diesel Engines. ............................... 23

Figure 7. America's Natural Gas Highway envisioned by Clean Energy. ........................ 24

Figure 8. Concentration of Truck Traffic. ........................................................................ 25

Figure 9. Waterway Freight Density................................................................................. 26

Figure 10. Existing Public and Private LNG Stations. ..................................................... 29

Figure 11. Diesel Prices Vs Natural Gas and LNG infrastructure costs........................... 30

Figure 12. Dynamic LNG station buildout scenarios under a 0.2% market penetration. . 34

Figure 13. Trucking route deployment across the under current 0.1% market penetration.

................................................................................................................................... 34

Figure 14. Dynamic LNG station build out scenarios under 0.1% market penetration.... 35

Figure 15. Dynamic LNG station price difference per diesel gallon equivalent under 0.1% 

market penetration. ................................................................................................... 36

Figure 16. LNG liquefaction plant build out scenarios under 0.1% market penetration. . 36

Figure 17. Dynamic LNG station build out scenario under 0.2% market penetration. .... 39

Figure 18. Dynamic LNG station price difference per diesel gallon equivalent under 0.2% 

market penetration. ................................................................................................... 39

Figure 19. LNG liquefaction plant build out scenarios under 0.2% market penetration. . 39

Figure 20. Trucking route deployment under 0.2% market penetration........................... 40

Figure 21. LNG delivered cost by station flow volume.................................................... 41

Figure 22. State incentives applicable to natural gas vehicles.......................................... 42

Figure 23. Static LNG station build out scenarios............................................................ 44

Figure 24. Static LNG plant build out scenarios............................................................... 44

Figure 25. Dynamic LNG refueling station build out scenarios under 0.2% LNG market 

penetration rate.......................................................................................................... 45

Figure 26. Dynamic liquefaction plant build out scenarios under 0.2% market penetration 

rate............................................................................................................................. 46

Figure 27. Dynamic LNG-Diesel price spread under 0.2% LNG market penetration 

($/gde)....................................................................................................................... 46

Figure 28. Dynamic CNG and LNG station build out under 0.2% market penetration rate.

................................................................................................................................... 47

Figure 29. LNG price swap process.................................................................................. 50

Figure 30. 100-year carbon intensity (gCO2e/mile) of C8 diesel and natural gas under 

different leakages rate. .............................................................................................. 56

Figure 31. Contribution to total carbon intensity of diesel and natural gas C8 trucks under 

current 1.12% leakage rate........................................................................................ 57
4

List of Tables

Table 1. NGVs range, fuel economy and cost differentials respect to diesel. .................. 27

Table 2. Breakeven fuel prices for NGVs by technology/storage configuration and 

payback period based on total annual mileage. ........................................................ 31

Table 3. Summary of Results by Scenario........................................................................ 38
5

Acknowledgements 

The authors would like to thank the California Energy Commission, GE Ecomagination, 

and the Sustainable Transportation Energy Pathways (NextSTEPS) consortium for 

financial support and intellectual contributions toward this research. 

The authors would also like to acknowledge researchers from Argonne National 

Laboratory, U.S. Department of Transportation, and California Air Resources Board, as 

well as Robert Harriss, Ian Sutherland, Daniel Sperling, Joan Ogden, Lew Fulton, 

Michael Farina, Brandon Owen, Karen Hamberg, and Graham Williams, who gave their 

valuable time and comments for this study.
6

Summary of Findings

 If recent, wide oil and gas price differentials hold, greater use of natural gas in the 

heavy-duty sector could potentially lower the cost of U.S. freight supply chains, 

thereby enhancing global U.S. competitiveness by lowering domestic fuel costs for 

long-distance trucking routes in certain regions. 

 The use of natural gas in the U.S. freight system improves energy security through 

geographic supply diversification.

 A concentrated regional focus in key markets for early investment is the least-cost 

strategy to initiate the development of natural gas transportation networks in the 

United States.

 In the case of LNG heavy-duty trucking networks, California is uniquely positioned to 

launch a profitable natural gas network. The costs to provide dedicated coverage for 

LNG across California are estimated to be less than $100 million. The Great Lakes 

and mid-Atlantic areas are also well-positioned to incubate a natural gas 

transportation network.

 Despite the fuel cost advantages that might result from some limited regional natural 

gas transportation network buildouts, the development of a U.S. national natural gas 

transportation network will be encumbered by high initial investment costs for new 

cross country infrastructure relative to the fully discounted, incumbent oil-based 

network.

 Lower levels of methane leakage will be required throughout the natural gas supply 

system in order to enable natural gas to provide a net greenhouse gas benefit relative 

to diesel. Technologies exist to facilitate this, but supportive policies may be required 

to encourage their adoption.

 The level of profitability of natural gas fueling infrastructure is more highly 

correlated with access to a high volume of traffic flows of freight movements than 

with the locus of surplus supplies of natural gas. Thus, initiatives to introduce natural 

gas freight fueling businesses in regions with stranded or inexpensive gas resources 

(natural gas supplies that lack sufficient demand to be commercialized) run a greater 

risk of failure than efforts to introduce natural gas fueling infrastructure along major 

freight routes in California, the Great Lakes region and the US Mid-Atlantic.

 The cost-benefit for natural gas as a direct fuel is most compelling for heavy truck 

fleets whose vehicles travel 120,000 miles a year or more.

 Current commercial economic drivers mean that conventional stations supported by 

mini-LNG facilities are likely to be the favored technology in the early stages of the 

market development. Additional options to supply CNG can be an enabling network 

feature.
7

 The lessons for natural gas apply more broadly to the question of the barriers to the 

development of national networks for alternative fuels. Generally speaking, the lower 

cost of alternative fuel is an important element of commerciality but is not the only 

driver to a successful transition to low carbon fuels. The level of costs of new 

infrastructure is also a significant variable to developing new networks, potentially 

creating region specific economics.

Background

Increasingly abundant natural gas supplies are significantly transforming the U.S. energy 

landscape. Innovations in horizontal drilling and hydraulic fracturing are unlocking vast 

unconventional reserves of U.S. domestic natural gas and oil. The so-called “shale 

revolution” has unleashed a giant surge in U.S. natural gas production that is making 

natural gas a competitively priced fuel in many different applications, including power 

generation, manufacturing and petrochemical production. Although differences exist in 

estimates of recoverable unconventional U.S. natural gas resources, the preponderance of 

geological and commercial assessments project that U.S. natural gas supplies will remain 

ample, lending credence to the possibility that natural gas could penetrate new markets. 

So far, the shale revolution is providing U.S. domestic natural gas at extraordinarily low 

prices. Liquefied natural gas (LNG) for trucks has seen a fuel price discount of $12-

$16/mmBTU (energy basis equivalent) over the past year. More recently, as both U.S. 

diesel and spot natural gas prices have declined, the price discount has decreased. At 

present, even with recent oil price declines, the oil–natural gas differential available on 

futures markets is averaging around $9-$10/mmBTU (energy basis equivalent) over the 

next one to three years forward. The price of natural gas is about $9.18/mmBTU (energy 

basis equivalent) less than oil in the derivatives markets for longer range future purchases 

(over the next five- to ten-years).

The emergence of natural gas as an abundant, inexpensive fuel in the United States has 

raised the possibility of a larger shift in the level of natural gas utilized in the 

transportation sector. The cost advantages of natural gas and the diversity of its 

geographical sources in North America raises the possibility that natural gas can increase 

the global competitiveness of the U.S. transportation supply chains. Commercial 

forecasts for how much natural gas could replace oil in transportation vary widely, with 

high end estimates in the millions of barrels per day (mbd).

1

That’s 5% to 10% of the 

total available market of about 13 mbd or more than 25% to 50% of the existing 3.9 mbd 

market for diesel. But questions remain about the commercial viability of natural gas in 

transportation given the broad investment required to create a national fueling 

 

1 In its June 2013 report, “Energy 2020:Trucks, Trains and Automobiles,” Citi Group projects that a shift to liquefied 

natural gas (LNG) for heavy trucking could eliminate 1.2 to 1.8 mbd of U.S. diesel demand by 2030 and 3.4 mbd 

globally.
8

infrastructure network and about the environmental performance of natural gas as a fuel 

for trucks. We investigate whether a shift to natural gas vehicles (NGVs) in the U.S. 

freight system can be commercially profitable and study the environmental consequences 

of such a transformation. 

The U.S. and Global Natural Gas Vehicle Fleet

Natural gas is already used as a transportation fuel in many applications in the United 

States and globally. There are currently 17.7 million natural gas vehicles operating 

worldwide, and 92% are light-duty vehicles. 2Iran and Pakistan represent the largest 

markets for NGVs at 3 million and 2.9 million, respectively. Other large markets for 

light-duty NGVs are India, China, Argentina and Brazil. 

Driven mostly by air quality concerns and an abundance of natural gas in some provinces, 

China has seen a rapid increase in the number of NGVs on the road, from 60,000 in 2000 

to more than 1.5 million today. Compressed natural gas (CNG) vehicles are predominant 

in China’s NGV market, including buses, taxis, private cars and commercial vehicles.

3

China’s national oil company CNPC (China National Petroleum Corporation) is 

projecting that natural gas use in transportation in China could rise to 54 billion cubic 

meters (bcm) by 2020, an annual growth rate of 16% a year. China’s 12th Five Year Plan 

encourages the development of liquefied natural gas (LNG) vehicles. The country 

currently has 70,000 LNG trucks on the road.

4

By contrast, there are 250,000 NGVs on the road in the United States including 14,000 

municipal buses and 4,000 medium and heavy duty trucks.

5 Roughly 3,600 LNG trucks 

are operating in the United States.

6 Nearly half of garbage trucks sold in the United States 

last year ran on natural gas. Only one automobile manufacturer, Honda Motor Co., offers 

a natural gas passenger vehicle for sale in the United States, but the car has so far failed 

to capture a large market base. 

Across the United States, there is a mature, robust distribution network for diesel fuel and 

gasoline. There are 59,739 diesel fueling stations and 121,446 gasoline stations, and 

2,542 truck stops where fuel is readily and conveniently available. This translates on 

average to about 20 truck stops for every 400 miles of interstate freeway. By contrast, 

there are just 800 CNG fueling sites, and just under half are public.7

To be successful, a new alternative fuel must offer the same convenience at a lower cost. 

Otherwise, governments must provide public incentives to investors to provide new 

 

2

http://www.ngvaeurope.eu/worldwide-ngv-statistics

3 UC Davis Institute of Transportation Studies China Workshop Beijing, China, October 2013

4 UC Davis Institute of Transportation Studies China Workshop Beijing, China, October 2013

5

http://www.ngvaeurope.eu/worldwide-ngv-statistics

6 www.afdc.energy.gov/vehicles/natural_gas.html

7

http://www.afdc.energy.gov/fuels/stations_counts.html
9

stations for an alternative fuel. The slow vehicle turnover and the prolific network of 

incumbent diesel fueling venues across the U.S. highway system limits the transition rate 

for alternative fuels. 

U.S. consumers are unlikely to adopt NGVs in large numbers because other, more 

convenient alternative fuel options are becoming available and those alternative fuel 

vehicles are perceived as more environmentally friendly and modern. By contrast, natural 

gas has high potential to make inroads as a fuel for commercial use, particularly for longdistance freight movement.

In the light-duty sector, U.S. consumers have not gravitated widely to NGVs. In a 2006 

U.S. National New Car Buyers survey, non-NGV drivers did not rate natural gas well, 

compared to alternatives, and ranked NGVs fifth after other options including “electric”, 

“all biofuels”, “hydrogen”, and “I have no idea.” Polling indicates that CNG is perceived 

as an older technology, in contrast to plug-in electric vehicles (PEVs) which are viewed 

to represent innovative, forward-looking technologies. The primary reason consumers 

buy NGVs is cheaper fuel and access to high occupancy vehicle lanes in urban centers. In 

contrast, fleet owners gravitate to NGVs to comply with clean air standards. Vehicle 

range and initial cost remain barriers. The Honda Civic NG, with improved fuel economy 

and acceleration, can go 248 miles without fueling, about 10% farther than the previous 

NG version, the Honda Civic GX, and has roughly a seven-year payback period.

The economic advantage of utilizing natural gas to save on fueling costs is highly 

correlated to both the relative efficiency of the vehicle and intensity of travel. In the 

United States, most individual drivers do not travel sufficient miles in daily driving to 

reap cost advantages from a switch to natural gas, given other attractive highly fuelefficient light-duty vehicle alternatives such as hybrids and PEVs.

8 But for commercial 

fleet vehicles, which regularly undertake intensive travel, natural gas can potentially offer 

cost savings and some environmental benefits. Figure 1 shows the annual fuel savings as 

a function of annual vehicle miles traveled under three different scenarios of LNG fuel 

discount to diesel.

 

8

For a more detailed analysis of the economics of CNG-fueled light duty vehicles, see Alan J. Krupnick, Will Natural 

Gas Vehicles Be in Our Future? Resources for the Future Issue Brief 11-06, May 2011
10

Figure 1. Annual Fuel Savings by Vehicle Miles Traveled

In this study we use a proprietary spatial modeling program to investigate the possible 

advantages and disadvantages of natural gas as a transportation fuel and its potential role 

in enabling other alternative fuels for the United States. In considering the future role of 

natural gas in U.S. transportation, we analyze vehicle applications where natural gas 

could potentially offer sustained fuel cost advantages in the commercial sector and 

investigate whether such fuel price savings would be sufficiently large to generate 

commercial drivers for construction of a national network of natural gas fueling 

infrastructure.

We also analyze the environmental impacts of a shift to natural gas compared to diesel in 

commercial applications. We consider what such a change in fuel type would mean both 

for air quality in terms of criteria pollutants (i.e., urban pollutants) and for cumulative 

greenhouse gas emissions. Finally, we use our results to consider whether a public role 

might be justified in the development of natural gas fueling infrastructure and, if so, 

where or how such an intervention might be most productive. Several U.S. states, 

including Oklahoma and Utah, have policies to promote natural gas vehicle use and 

investment. We investigate the optimum locations for such public policy measures and 

the specific benefits that might result from a shift to natural gas as a transport fuel in 

those locations. 

($10,000)

($5,000)

$0

$5,000

$10,000

$15,000

$20,000

$25,000 Annual Fuel Savings

Annual Vehicle Miles Traveled

Diesel $3, LNG $2.50/dge Diesel $3, LNG $2.30/dge Diesel $3, LNG $2.00/dge

$.70 discount per dge, LNG 

$0.02 cheaper per mile 

$.50 discount per dge, 

LNG $0.02 more expensive per mile 

$1.00 discount per dge, 

LNG $0.08 cheaper per mile 
11

We begin by summarizing our findings and then proceed to discuss cost, technical and 

environmental issues in more detail. We conclude with a policy analysis discussion based 

on our findings. 

Freight Supply Chain Competitiveness 

Natural gas station developer Clean Energy recently estimated that the cost benefit of 

natural gas as a fuel is most compelling for heavy truck fleets whose vehicles travel over 

90,000 miles a year or more9. Our results support this analysis in part. Further, we find 

that greater use of natural gas in the heavy-duty sector could potentially lower the cost of 

U.S. freight supply chains and thereby enhance competitiveness and energy security. In 

particular, we find that while NGVs can be more expensive upfront than conventional 

diesel-powered medium- and heavy-duty vehicles, the fuel savings can produce attractive 

payback for natural gas fleet owners in less than three years.

Of course, this result is sensitive to changes in the price differential between diesel and 

natural gas. The cost advantage for LNG compared to diesel has been hovering around 

$8-$16/mmBTU in recent years but has narrowed recently with the crude oil price 

collapse in the second half of 2014. A significant differential remains since the spot price 

of U.S. natural gas has declined 30%, while U.S. diesel prices have also dropped 25% 

since the summer. Fuel switching will be based on long term price trends, where natural 

gas supplies at present appear to be more prolific and less risk prone than oil. 

Energy Security through Geographic Diversification

A shift to natural gas in the freight sector provides key energy diversification benefits to 

the nation. It brings the transportation sector in line with America’s power sector—where 

electricity providers can choose between a half a dozen fuels other than oil. The result is

more flexibility, increased price competition and greater security of supplies. On the 

power sector side, supply and price competition from natural gas and other diverse fuels 

have benefited the U.S. economy and average Americans resulting in lower electricity 

prices and increased global competitiveness, according to studies by the Congressional 

Research Service and other think tanks.

10 The shift to natural gas from coal has also 

contributed to a 10% drop in U.S. greenhouse gas emissions between 2005 and 2012.11

Similar benefits could come from a greater diversity of fuel choices in the transportation 

sector. 

 

9 UC Davis Natural Gas Workshop February 2013

10 http://fas.org/sgp/crs/misc/R42814.pdf

11 http://www.scientificamerican.com/article/us-greenhouse-gas-emissions-fall-10-since-2005
12

In the case of natural gas as a transportation fuel, we find that the diverse geographic 

location of U.S. natural gas supplies offers a strategic and economic benefit. Greater 

geographical diversity of domestic energy supply sources is a key benefit coming from 

the shale oil and gas boom and thus could similarly be transferred into the transportation 

sector by adoption of natural gas as a heavy-duty vehicle fuel. Shale gas geologic 

formations are distributed across the country with natural gas production disseminating 

from onshore shale gas abundance not only in the U.S. Southwest, but also in the U.S. 

Northeast, Midwest and North Dakota. This broad geographic distribution across the 

country helps shore up supply resiliency. In contrast, imported oil and traditional U.S. 

domestic oil reservoirs and oil refining infrastructure are heavily concentrated in the Gulf 

of Mexico and interruptible by severe storms. Shale gas is, in fact, ushering in a changed 

paradigm where consuming countries like the United States will increasingly be able to 

source their supply at home, lowering geopolitical and weather and climate changerelated risks and enhancing economic benefits.12

Least Cost Options 

The geographic diversity of natural gas supply opens the question to the optimal locations 

to build natural gas fueling infrastructure. To answer this question we use a modeling 

framework that utilizes spatial mapping of existing major interstate highways, trucking 

routes, key fueling routes for fleets and heavy-duty trucks, and fueling infrastructure for 

CNG for fleet operation and LNG for long-haul trucks to make infrastructure planning 

decisions. Spatial network theory and network analysis are used to calculate the most 

profitable trucking corridors to establish LNG infrastructure.13

Our special optimization model is designed to determine the most profitable

transportation networks and locations for natural gas flows into transportation markets in 

California and nationwide. Our model uses the spatial infrastructure data and compares

costs for transportation of natural gas by source, distribution method, and other market 

development variables through mathematical optimization. In other words, we study 

where the most cost-effective and profitable locations to build natural gas fueling 

infrastructure would need to be located in order to minimize the costs of an overall 

national system of natural gas fueling along major inter-state highways. Our inquiry 

assumes that all commercial players would benefit most from a system that would allow 

the widest number of stations at the lowest possible cost per total capital deployed and 

cheapest available fuel. Our main study finding is that concentrated regional focus in key 

 

12 Medlock, Kenneth, Amy Myers Jaffe, Meghan O'Sullivan, "The Global Gas Market, LNG Exports and 

the Shifting US Geopolitical Presence," Energy Strategy Reviews, Special Issue, Current and Emerging 

Strategies for US Energy Independence, December 2014

13 Allen Lee, Nathan Parker, Rosa Dominquez-Faus, Daniel Scheitrum, Yueyue Fan, Amy Myers Jaffe, 

“Sequential Buildup of an LNG Refueling Infrastructure System For Heavy Duty Trucks” Proceedings 

and Presentation to Transportation Research Board Annual Meeting, January 2015
13

markets for early investment is the least-cost strategy for developing a broader national 

network over time.

High Traffic Density Routes: California’s Unique Characteristics

The cost benefit for natural gas as a direct fuel is most compelling for heavy truck fleets 

whose vehicles travel 120,000 miles a year or more. However, despite the cost 

advantages of natural gas fuel, the development of a national natural gas transportation 

network will be encumbered by high initial investment costs relative to the low operating 

costs for the incumbent oil-based network. Compared to the incumbent fuel, the lower 

cost of alternative fuel is an important element to commerciality, but is not the only 

driver to a successful transition. The costs of new infrastructure are also a significant 

variable to developing new networks. 

To overcome the competitive hurdle posed by incumbent stations, our research finds that 

traffic volume is a more important success factor than the location of surplus natural gas 

supplies. The availability of cheap natural gas in locations such as Pennsylvania or Texas 

is less relevant than the overall density and volumetric flow of trucking. In other words, 

locations with stranded gas, that is gas that is located somewhere with insufficient access 

to possible buyers, are not necessarily the best locations for natural gas freight fueling 

businesses. Instead, we find that geographically dense and high volume freight corridors 

provide the most optimum locations for new investment in NGV fueling infrastructure, 

especially if coupled with higher than average retail diesel prices. Supportive state 

policies can also be influential if other conditions are prime. The best example of this is 

the state of California, which meets all of these criteria, including a robust freight 

corridor, high diesel prices compared to the rest of the country, and a carbon pollution 

credit market. 

Our study shows that California’s heavily trafficked Interstate 5 (I-5) corridor, which 

hosts almost all of the long-haul truck travel in the state, would provide investors with the 

most favorable commercial opportunity to initiate a concentrated profitable network of

LNG fueling stations that might someday seed a possible expansion to a wider, national 

network. Because truckers have fewer options to travel outside route I-5, the initial costs 

for building a profitable NGV fueling network in the state are lower than in other parts of 

the country where multiple roads must provide dense station coverage. In addition, traffic 

flows on I-5 are robust compared to the national average, increasing the potential sales 

rate from any particular station location on the route. We calculate that an initial 

investment of under $100 million (under assumptions for a 12% return on capital) could 

be sufficient to start the launch of a dedicated network along I-5. However, in order for 

this investment to be effective, the market for LNG trucks must first reach 6,000 vehicles 

nationwide, or about twice current levels. Further, California is a potentially attractive 

location for a prospective natural gas transportation network because California-based 

fleet operators currently enjoy a 20% credit benefit under the Low Carbon Fuel Standard 
14

(LCFS). (Fossil natural gas currently has a 20% lower carbon score than diesel under the 

LCFS, although a regulatory proposal could shrink this percent reduction).

The other region that appears to have high enough demand to support early adoption of 

LNG as a trucking fuel is the Great Lakes area, which, like California, sees a high 

volume of traffic and experiences higher diesel prices. It is possible that a national 

network could evolve over time as more regionally profitable routes in California and the 

Great Lakes region proliferate outwards. Counter to popular thinking, the profitability of 

LNG stations is most tied to intensity of traffic flows and higher than average local 

petroleum prices than to ample availability of local natural gas, our modeling shows. 

These results paint a potentially positive picture for construction of infrastructure that 

might promote an easy transition from LNG to renewable natural gas in heavy trucking in 

the state of California as desired by state policy makers.

14

California may have stronger interest in assisting the development of an LNG fueling 

network for heavy-duty trucking in the state – but only if vehicle efficiency and capture 

of production and distribution system leakage could be improved to add to environmental 

benefits. Still, the construction of an LNG refueling infrastructure system for heavy-duty 

vehicles would also enable the greater use of biogas, which might argue for state support 

if NGVs could be equal to or slightly better in their overall environmental performance 

than diesel. Consumption of biogas in transportation in California increased by an order 

of magnitude in one year jumping from 1.7 million gallons of diesel equivalent (dge)

during the year beginning in Q3 2012 to 17.5 million dge the following year. During this 

time, biogas represented 4% of low carbon fuel credits generated for the state and has a 

substantial growth potential.

The construction of natural gas infrastructure would be enabling to biogas producers who 

would be assured that fueling networks would be available to commercialize their 

production. California and neighboring states have a biogas resource base that is large 

enough to support between 10,000 and 30,000 LNG trucks, but further study is needed to 

determine what distant resources could be developed and imported profitably from other 

states and nearby countries. The California Biomass Collaborative, a University of 

California Davis-led public-private partnership for the promotion of California biomass 

industries, estimates that 32.5 million billion dry tons (bdt) of in-state biomass feedstocks 

could be available for conversion to useful energy15 In particular, estimates for methane 

production from landfill gas are 55 bcf/year, 4.8 bcf/year for waste water biogas, and 14.6 

bcf/year for biogas from manure sources. Similar biomass resources are located in states 

 

14 Our independent academic research findings support the rationale for US Department of Energy efforts to create 

Interstate Clean Transportation Corridors and add new insights into the most economically optimum locations for such 

corridors. For example, see Stephanie Meyn (2012) Greener Alternatives for Transportation Corridors, Presentation to 

the US Department of Energy Clean Cities Program, West Coast Collaborative Partners Meeting. In 1996, similar ideas 

were presented by Bruce Resnik, on Alternative Fuels Trucking, NREL

15 Williams, R. B., Gildart, M., & Jenkins, B. M. (2008). An Assessment of Biomass Resources in California, 2007. 

CEC PIER Contract50001016: California Biomass Collaborative., (http://biomass.ucdavis.edu/files/reports/2008-cbcresource-assessment.pdf)
15

that border California or along routes for the transmission of natural gas to the state from 

major producing states. 

We estimate that the methane potential from landfill gas in the Western states outside of 

California is 105 bcf/year based on existing and candidate landfills identified by the

EPA.

16 Parker estimates an additional 100 million bdt/year of lignocellulosic biomass in 

the Western states which are roughly equivalent on an energy-content basis to the 

gasoline used by 14.5 million passenger cars a year. However, some of these in-state and 

external biomass sources are already committed to or could be used for the production of 

liquid biofuels or for dedicated power generation services to the businesses where they 

are co-located17.

Barriers to Entry: High Capital Costs for New Infrastructure 

Despite the cost advantages of a regional natural gas transportation network build-out, 

the development of a national natural gas transportation network will be encumbered by 

high initial investment costs relative to the low cost operations of the existing incumbent 

oil-based network. Thus, we find that commercial factors will not be sufficient to 

overcome the infrastructure capital and operational costs that must be considered in any 

competition with the widely disseminated, fully discounted incumbent infrastructure for 

diesel fuel all over the United States in a matter of just a few years. 

Our analysis concurs with other alternative fuels research that demonstrates how the 

capital intensity of fueling station investments makes it difficult for new fuels to compete 

with incumbent oil-based fuels that benefit from mature, financially amortized 

distribution networks. The case of natural gas is more glaring than other promising fuels 

such as hydrogen or liquid biofuels because natural gas has as its starting point a 

substantial fuel cost discount compared to diesel, its incumbent competitor. Even though 

major corporations have begun investing billions of dollars to build infrastructure to feed 

natural gas into the U.S. trucking industry and expand the use of natural gas in fleets, 

natural gas’ success as a transport fuel is by no means guaranteed. 

Thus, a focused, regional approach that would lay the groundwork for expansion over a 

longer period of time would be most productive to tap the benefits of rising U.S. natural 

gas supply for transportation uses. Our scenario analysis shows that even a return to lofty 

diesel prices such as those seen in July 2008 would not significantly alter this conclusion 

because even this wider cost incentive does not create a sufficient economic environment 

to finance the wide gap needed for infrastructure capitalization. And a 50% government 

 

16 “Landfill Methane Outreach Program: Energy Projects and Candidate Landfills.” US EPA, 

(http://www.epa.gov/lmop/projects-candidates/index.html)

17 Parker, Nathan, Peter Tittmann, Quinn Hart, Richard Nelson, Ken Skog, Anneliese Schmidt, Edward Gray, and 

Bryan Jenkins. “Development of a biorefinery optimized biofuel supply curve for the Western United States.” Biomass 

and Bioenergy (2010) (34), pp 1597-1607.
16

subsidy for LNG fueling stations similarly would not be effective in solving the problem 

of station unprofitability in many locations across the United States, our research shows.

Carbon Intensity and Air Quality Considerations of Natural Gas in 

Transportation 

The benefit of natural gas on a net carbon intensity basis in transportation is less clear. In 

terms of climate pollution, tailpipe carbon dioxide emissions from burning natural gas in 

heavy-duty trucking applications are roughly one fourth to one third as compared to 

burning gasoline or diesel. 

18

. But for spark ignition LNG trucks to match high-efficiency 

diesel trucks in life-cycle carbon intensity, methane leakage from the natural gas 

production and distribution system must be negligible. If the more efficient (and 

expensive) HPDI engine is used in LNG trucking, analysis shows, system methane 

leakage must be under 2.8% for natural gas to break even in carbon intensity. In addition, 

a large improvement in natural gas vehicle efficiency would be necessary for natural gas 

to compete effectively against future best-in-class diesel engines in life-cycle greenhouse 

emissions. 

Generally speaking, natural gas-based fuels emit less particulate matter and sulfur 

components than diesel. Vehicle modeling research shows that a shift to LNG fuel can 

contribute a significant reduction in SOx tailpipe emissions as well as almost a full scale 

elimination in fine particulate matter in heavy-duty trucks. Regions with heavy use of 

diesel and bunker fuel (marine ECAS, ports, industrial sites, and roads with dense heavytruck traffic or other non-attainment areas where diesel is heavily used) could experience 

substantial air quality improvements by switching to natural gas-based fuel. The scientific 

literature also suggests that aftertreatment technology is more important than the type of 

fuel used and, thus, this must also be taken into account for California to garner the 

optimum air quality benefits from a shift to natural gas in heavy-duty trucking. For 

example, diesel engines with particulate filters could produce lower levels of particulates 

than natural gas engines not equipped with aftertreatment technologies, but when NGV

engines are equipped with three-way catalyst technology they generally produce much 

lower particulate and SOx emissions than updated diesel engines. Similarly, NGV

engines without aftertreatment have less ability to control formaldehydes and NOx 

pollution but with appropriate technology they could produce similar or lower levels than 

diesel19.

 

18 Hengbing Zhao, Andrew Burke, Lin Zhu “Analysis of Class 8 Hybrid-Electric Truck Technologies 

Using Diesel, LNG, Electricity, and Hydrogen, as the Fuel for Various Applications” Proceedings of 

EVS27 Barcelona, Spain, November 17-20, 2013

19 Yoon S, Collins J et al, Criteria pollutant and greenhouse gas emissions from CNG transit buses 

equipped with three way catalysts compared to lean-burn engines and oxidation catalyst 

technologies, Journal of Waste Management, 2013 August, (8) 926-33
17

The Case for Natural Gas: An Abundant, Domestic Fuel 

A primary consideration for the adoption of natural gas as a key transportation fuel in the 

U.S. heavy-duty trucking sector is whether natural gas will remain in abundant supply, 

holding prices relatively low compared to oil-based fuels. U.S. gross natural gas 

production has risen from an annual average rate of 64.3 billion cubic feet per day (bcfd) 

in 2005 to 82.7 bcfd in 2013, driven primarily by momentous growth in production from 

shale from less than 4 bcfd to more than 31 bcfd. Natural gas supplies from the Marcellus 

formation in the U.S. Northeast have gained tremendous ground in the past year, altering 

historical patterns for oil and gas flows inside the United States and creating new 

opportunities. 

In 2011, Advanced Resources International (ARI) estimated 1,930 trillion cubic feet (tcf)

of technically recoverable resource for North America and 6,622 tcf globally, with over 

860 tcf in U.S. gas shales alone. 20 Most recently, the U.S. Energy Information 

Administration (EIA) commissioned assessments from Intek in 2011 and another 

assessment from ARI in 2013. The Intek study estimated 750 tcf of recoverable shale gas 

resources in the U.S. Lower 48. ARI increased its U.S. shale estimate to 1,161 tcf, as part 

of a global assessment of shale resources of a world total of 7,299 tcf.21 As more drilling 

has taken place, information about the size and economics of recoverable U.S. 

unconventional resources has improved. While concerns about sharp initial production 

decline rates have emerged, enhanced understanding about long term performance at 

fields and the closer distribution of infill drilling has increased optimism about the 

potential for improved recovery rates. 

 

20 “World Gas Shale Resources: An Assessment of 14 Regions outside the United States, a report prepared by 

Advanced Resources International (ARI) for the United States Energy Information Administration (EIA) April 2011.

21 “A Review of Emerging Resources U.S. Shale Gas and Shale Oil Plays” Prepared by INTEK Inc. for US Energy 

Information Administration. July 2011.
18

Figure 2. Shale Resources in North America22

Several organizations have studied the ARI, Intek and other assessments such as 

Rogner23 and concluded that this large natural gas resource base will allow U.S. natural 

gas prices to remain relatively low for an extended period of decades, even if North 

American exports occur (barring a major unexpected disruption in global supplies). 

NERA Economic Consulting in a report prepared for the U.S. Department of Energy in 

2012 analyzed multiple U.S. liquefied natural gas scenarios under EIA’s high, low, and 

reference case for U.S. oil and gas resources. NERA’s analysis found that average U.S. 

natural gas prices generally remain within the $4.00–$5.00 per thousand cubic feet (mcf)

range, under most of the export scenarios studied and below $3.50/mcf under high 

resource scenarios for the study period to 2040.24

Another study by Rice University’s Baker Institute, University of California, Davis, and 

Harvard University projects that U.S. Henry Hub spot prices will average $4.00–

$6.00/mcf to 2030 under a status quo case where U.S. LNG exports average around 5 to 6 

bcfd (Figure 2). Under a high export case of 12 bcfd, study researchers project that U.S. 

natural gas prices would be about $0.20 higher in the 2020s and $0.40 higher in the 2030s 

as compared to the status quo case.25

 

22 Source: Gallery of World Hydrocarbon Endowment & Shale Gas Resources, Al Fin Energy blog at 

http://alfin2300.blogspot.com/2012/03/gallery-of-world-hydrocarbon-endowment.html

23 H.H. Rogner, "An Assessment of World Hydrocarbon Resources" Annual Review of Energy and Environment, 1997

24 NERA Economic Consulting http://www.nera.com/publications/archive/2014/updated-macroeconomic-impacts-oflng-exports-from-the-united-sta.html

25 Medlock, Kenneth, Amy Myers Jaffe, Meghan O'Sullivan, "The Global Gas Market, LNG Exports and the Shifting 

US Geopolitical Presence," Energy Strategy Reviews, Special Issue, Current and Emerging Strategies for US Energy 

Independence, December 2014
19

Figure 3. Henry Hub Price, 2000-2030, according to Rice Model Status Quo 

Scenario (Real 2010$)26

Medlock (2014) studies the average expected ultimate recovery (EUR), drilling costs and 

break even prices for key U.S. shales. He finds that there is an estimated 1060 tcf of shale 

gas resource recoverable across North America at prices below $6/mcf, and almost 1,450 

tcf at prices below $10/mcf (Figure 3)

 

26 Source: Baker Institute CES Rice World Gas Trade Model, vApr14 (Medlock). For much more detail on modeling 

approach and results see the CES working papers “U.S. LNG Exports: Truth and Consequence,” 2012, available at 

http://bakerinstitute.org/research/us-lng-exports-truth-and-consequence; and “Natural Gas Price in Asia: What to 

Expect and What it Means,” 2014, available at http://bakerinstitute.org/research/natural-gas-price-asia-what-expectand-what-it-means. Both are authored by Ken Medlock.
20

Figure 4. Estimated Expected Ultimate Recovery by Shale Play per Average Well by 

Location27

Figure 5 represents the average breakeven price by shale play in North America. Medlock 

(2014) concludes that about 246 tcf of the available resource at a breakeven price of 

under $6/mcf is in Canada, 111 tcf is in Mexico, and the remaining 656 tcf is in the 

United States. At prices under $10/mcf, 358 tcf is in Canada, 215 tcf is in Mexico, and 

874 tcf is in the United States. Finally, Medlock notes that the total technically

recoverable resource associated with Figure 5 is 1,844 tcf, where almost 400 tcf of the 

technically recoverable resource is commercially viable only if prices are at a minimum 

of $10/mcf.

 

27 Source: Baker Institute CES Rice World Gas Trade Model, Apr14 (Medlock)
21

Figure 5. North American Shale Gas Resource and Average Breakeven Price by 

Play.

The above analysis supports the notion that the North American natural gas resources 

have a relatively elastic supply curve at affordable prices. But natural gas’ price 

attractiveness as a substitute for diesel fuel is also predicated on the durability of the 

sizable gap between relatively inexpensive natural price levels as compared to lofty oil 

price levels, and some uncertainty remains about long term trends for global oil prices.

Rising tight oil resource development in North America combined with advances in 

automotive and other energy efficiency technologies are currently placing downward 

pressure on oil prices and could be part of a cyclical downturn,28 but natural gas prices 

have also been declining of late. In recent months, spot prices of U.S. diesel have fallen 

roughly 25% while the price of U.S. natural gas has declined 30%. At present, the oil–

natural gas differential available on futures markets is averaging around $9-$10/mmBTU

equivalent from one year forward to three years forward. The long range derivatives 

differential is about $9.18/mmBTU equivalent cheaper. The possibility that natural gas 

prices could remain relatively affordable compared to diesel prices has increased interest 

in natural gas applications for transportation. 

 

28 El-Gamal, Mahmoud Amin and Amy Myers Jaffe (2013) Oil Demand, Supply and Medium Term Price Prospects: A 

Wavelets-Based Analysis. Institute of Transportation Studies, University of California, Davis, Research Report UCDITS-RR-13-10
22

The U.S. Freight Supply Chain and Potential for Natural Gas

Over 70% of all freight tonnage transported inside the United States moves by trucks. A 

high proportion of this movement of goods by trucks concentrates on the Interstate

Highway system where some 2.5 million Class 8 heavy-duty vehicles carry 8.2 billion

tons of goods a year. In addition, there are roughly 1.3 million medium-duty trucks in 

service in the United States29. Heavy-duty vehicles are defined as those in the highest 

weight class of 33,001 lbs. and over and include truck tractors, dump trucks, and cement 

trucks. Medium-duty vehicles are defined as service vehicles with weights of between 

19,501 lbs. and 33,000 lbs., including a wider variety of trucks such as single-axle trucks, 

city transit buses and smaller truck tractors. Heavy-duty vehicle classes include classes

8B, (67%), 6 (14%), 8A (8%), 7 (5%), and Class 3 (1%).

The size of the U.S. diesel fuel market is approximately 41 billion gallons a year

(excluding military). Heavy-duty vehicles represent about 62% of this market, with 

roughly 23-25 billion gallons per year demand coming from line-haul Class 8 trucks. 

Currently, there are only 9,500 truck stations in the United States that serve 1.5 million

Class 8 trucks. Class 8 trucks use 30 billion gallons per year diesel consumption, the 

equivalent to 3.3 tcf/year natural gas or 10 to 15% of current U.S. natural gas 

consumption.

According to the EIA, annual demand for diesel fuel from freight trucks could rise to as 

much as 45 billion gallons under a business as usual forecast by 2025 or about double 

current use. Thus, the potential of natural gas to diversify the U.S. freight system away 

from oil is large.30

The heavy-duty trucking industry shifted from gasoline to diesel fuel after the 1970s oil 

crises in an effort to save money on fuel. The shift was slow in the 1950s but then ramped 

up quickly to 50% of the market after 10 years, and 100% of the market after the 1970s 

oil crises created competitive forces which gave firms switching to diesel fuel from 

gasoline a competitive advantage.31 The rate of technology adoption is shown in Figure 

6,

32 which represents the transition to diesel’s share of new sales of Class 8 trucks in the 

United States starting in the 1960s. 

 

29 http://www.afdc.energy.gov/vehicles/natural_gas.html

30 In the U.S. the heaviest trucks consume an average of roughly 6.5 gallons per thousand ton-miles. However, fuel 

efficiency of the existing truck fleet varies by weight range, drive cycle and terrain. In 2014, the Cummins/Peterbilt 

team announced their fully-loaded class 8 truck achieved a fuel economy of 10.7 miles per gallon. 

31 LNG as a Fuel for Demanding High Horsepower Engine Applications: Technology and Approaches, 

Paul Blomerus 2012. Page 6.

32 LNG as a Fuel for Demanding High Horsepower Engine Applications: Technology and Approaches, 

Paul Blomerus 2012. Page 6.
23

Figure 6. Percent of New Class 8 Truck Sales with Diesel Engines.

Because the turnover rate for new trucks for large fleets among first owners is relatively 

swift (i.e., three to four years) and natural gas is abundant and has seen a price advantage 

compared to diesel of between $1.50 and $2.00 a gallon over the last two years, there has 

been a growing interest in natural gas as a fuel for long distance trucking. In its report, 

“Energy 2020: Trucks, Trains and Automobiles,” Citi projects that a shift to liquefied 

natural gas (LNG) for heavy trucking could eliminate 1.2 to 1.8 million barrels per day 

(mbd) of U.S. diesel demand by 2030 and 3.4 mbd globally. 

At least two firms, Clean Energy Fuels, and ENN have begun building LNG fueling 

stations in the United States. There are currently 59 public LNG fueling stations and 42 

private LNG fueling stations along routes from Los Angeles to Las Vegas, around 

Houston and around Chicago. The stations currently serve a fleet of 3,600 LNG trucks. 

California is the state with the largest number of LNG fueling stations, serving over 

200,000 gallons a day, with local facilities in Tulare, Lodi, Fontana, Lost Hills, San 

Diego, Aurora and Ripon, among others. Zeuss Intelligence reports that there are 34 LNG 

supply plants with trailer loadout capable of producing about 3 million gallons of LNG a 

day33. The United States has over 800 CNG fueling sites of which a little under half are 

public.34

 

33 Provided to authors by Zeuss Research consultants

34 http://www.afdc.energy.gov/fuels/stations_counts.html
24

Clean Energy is the largest natural gas fuel provider in North America with over 330 

natural gas fueling stations, serving 660 fleets and 25,000 vehicles. The company 

currently sells an average of 200 million gallons of CNG and LNG a year. The projected 

America’s Natural Gas Highway (ANGH) by Clean Energy includes 150 natural gas

stations spread out every 200–300 miles. Clean Energy says it is able to achieve a return 

on capital for fueling station investment and still pass on between $1.00–$1.50 a gallon in 

fuel savings to customers. Figure 7 shows Clean Energy’s American Natural Gas 

Highway.

Figure 7. America's Natural Gas Highway envisioned by Clean Energy.

The company’s business model is to line up with return-to-base segment shipping that is 

enabling a shift to LNG fuel. Increasingly, long distance trucking is changing from 

patterns where a single vehicle with a single driver transverses the entire country to a hub 

and spoke operation where more localized fleets handle part of a longer journey for 

modular containers.35 This new transport paradigm means more trucks return to a local 

home base in the evening, not only improving the lifestyles of drivers but also creating 

more opportunities to fuel and maintain fleets from a home base. This emerging “relay 

 

35 For more details on this phenomenon and its potential to enable LNG as a trucking fuel, see Alan J. Krupnick, Will 

Natural Gas Vehicles Be in Our Future? Resources for the Future Issue Brief 11-06
25

race” supply chain model to daily regional operations with a home base is conducive to a 

shift to natural gas for fleets. 

Some U.S. trucking corridors have heavier traffic than others and may therefore be better

suited for a shift to natural gas than less traveled routes. Among the highest traveled 

trucking corridors I-5 in California; Milwaukee to Chicago; upstate New York, New 

York City and New Jersey; Dayton, Ohio to Cincinnati; routes around the Kansas City 

region; Chicago to Indiana; Dallas to Houston and Orlando to Tampa. Routes such as I-5 

in California where truckers have fewer alternative routes to choose from offer the best 

potential for alternative fuels because they can support a dedicated network with the 

highest chances that the majority of trucks will pass a particular station. As might be 

expected, several of these highly trafficked routes also tend to have the highest diesel 

prices in the nation. Diesel prices averaged 9% to 10% above the national average in New 

York and Pennsylvania in 2013. Diesel prices in Ohio, Michigan and New England 

average about 5% above the national average, while California, Delaware and Maryland 

prices are 2% above the national average and Indiana prices are 3% above the national 

average.

Figure 8 shows the concentration of trucking traffic on U.S. interstates with thickness of 

dark red shading representing those routes with the heaviest truck traffic flows. As the 

figure shows, California and the Great Lakes region are among the heaviest flows in the 

United States and therefore may have the highest potential for a new fuel. 

Figure 8. Concentration of Truck Traffic.
26

This concentration of truck traffic in the U.S. supply chain to certain regions 

complements the patterns of movements of goods by ship as shown in Figure 9.

Figure 9. Waterway Freight Density. 36

Barriers to Commercial Adoption of Natural Gas in Long-Distance 

Trucking

Vehicle cost

Despite some recent gains in network development, natural gas faces the same chickenegg problem as other alternative fuels. Two major commercial barriers exist. The first 

commercial barrier is that LNG trucks cost significantly more than diesel trucks. The cost 

varies depending on the actual model. The components that add to cost are the engines, 

 

36 http://www.ops.fhwa.dot.gov/freight/Memphis/appendix_materials/lambert.htm
27

which can be either compression ignition (CI) or spark ignition (Si), and the natural gas 

onboard storage systems, which can be either CNG or LNG. 

Ignition in the Ci engines requires injection of a small amount of diesel fuel although the

engine is operated on natural gas. As shown in Table 1, the cost of the CI engine is far 

more expensive than a diesel engine at a $25,000–$30,000 premium. The Si engine is 

only $1,000–2,000 more expensive than the diesel engine of the same displacement but 

performs at a significantly lower rate of fuel efficiency. The fuel economy of trucks using 

the dual-fuel CI engines are close to those using a diesel engine, while the fuel economy 

with the Si natural gas engine is about 10-20% less than with the diesel engine

The cost ($/dge) of storing natural gas as LNG is 20–25% higher than storing it as CNG,

but offers some advantages in lighter volume and weight. For the same size storage unit, 

the range using LNG will be twice that of CNG due to differences in energy content per 

an equal volume of each fuel. The longest range will be attained using a LNG CI truck 

because of the higher fuel economy of the dual-fuel CI engine and the higher energy 

density of the fuel. However, as indicated in Table 1, the differential cost of the LNG CI 

truck will be higher than that of the CNG Si unit due to higher cost of both the dual-CI 

engine and the LNG storage. .

The least expensive NGV option would therefore be CNG storage and Si engines. Using 

the cost values in Table 1, for a range of 700 miles, the cost of a CNG Si truck would be 

$7,900 lower than the LNG CI truck. The CNG Si truck would carry a price premium of 

$36,298 over a diesel truck. The more efficient CI model with the LNG storage would 

have a premium of $44,168. 

Table 1. NGVs range, fuel economy and cost differentials respect to diesel.

Vehicle Range 

(miles)

Fuel 

economy 

(mpdge)

Engine

Cost 

($)

Storage

Cost ($)

Incremental 

cost to 

OEMs ($)

Incremental 

cost to 

Consumers 

($)

Diesel 900 5.6 9,000 1,000 0 0

LNG Ci 700 5.4 20,000 35,200 45,200 67,800

LNG Si 570 4.4 10,000 35,000 35,500 38,200

CNG Ci 370 5.4 20,000 15,000 25,400 38,100

CNG Si 300 4.4 10,000 15,000 16,500 24,500
28

Cost of the refueling infrastructure 

The second barrier is that LNG and CNG fuel cannot leverage existing filling station 

equipment but requires a new set of fueling apparatus.37 Across the United States, there is 

a mature, robust distribution network for diesel fuel and gasoline. There are 59,739 diesel 

fueling stations and 156,065 gasoline stations in the United States and 2,542 truck stops 

where fuel is readily and conveniently available. This translates on average to about 20 

truck stops for every 400 miles of Interstate freeway. 

Despite attractive fuel cost differentials and freight customers’ interest in cleaner 

transportation fuel options, the trucking industry has to date been reluctant to take the 

plunge on expensive equipment upgrades to natural gas. 

The logistics sector operates on thin margins and tight schedules, and fueling station 

density is a critical issue. LNG trucks are dedicated vehicles, meaning they must have 

LNG station coverage that enables their full range of operations. But the penetration rate 

of LNG along major highways with the highest flows of goods by heavy-duty truck 

represents less than 0.1% of the national market. This presents a chicken and egg problem 

in transitioning to a significant market share for LNG trucks.

Drivers need to stop to refuel as infrequently as possible and natural gas’ reduced density 

of fuel means more time-consuming stops for fueling. The distance to a vehicle 

maintenance technician with natural gas vehicle repair skills is also a consideration for a 

trucking route. For long-haul shippers, natural gas stations must be provided along routes 

every 300–400 miles, whereas diesel fuel stations can be spaced over 1,000 miles apart. 

Natural gas stations must be available along the entire route for it to be viable for truck 

fleets to shift to NGVs. To date, despite the strongest market for commercial truck sales 

in almost a decade, momentum towards the use of natural gas in long-distance heavyduty truck fleets has been waning.38 At present in the United States, there are only a few 

major shipping routes that have full coverage for LNG fueling (Figure 10).

 

37 It is possible to reduce some of the land and facilities cost by locating natural gas fueling infrastructure contiguous 

to traditional truck stops as has been done in some limited locations, but the cost of the fueling infrastructure itself 

remains a barrier. 

38 Bob Tita “Slow Going for Natural Gas Powered Trucks” The Wall Street Journal, August 25, 2014
29

Figure 10. Existing Public and Private LNG Stations. 39

A core issue blocking the construction of a comprehensive national network for natural 

gas fueling is the capital intensity of new fueling station investments which have to 

compete against sales outlets of incumbent fuels whose distribution networks are fully 

depreciated. In effect, natural gas’ price discount would have to be large enough to cover 

both the high capital costs for building out new stations and higher operating costs for 

LNG fuel as illustrated below in Figure 11. 

 

39 http://www.afdc.energy.gov/locator/stations/
30

Figure 11. Diesel Prices Vs Natural Gas and LNG infrastructure costs.

The level of vehicle turnover and the prolific network of incumbent diesel fueling venues 

across the U.S. highway system limits the transition rate for alternative fuels and means 

that a new, alternative fuel must offer the same convenience at a lower cost. Otherwise, 

governments must provide public incentives to investors to provide new stations for an 

alternative fuel. Thus, the conversion of heavy-duty fleets to a new fuel is unlikely to take 

place rapidly because only 200,000 to 240,000 new vehicles come on the road each year. 

At present only 14% of fleets operate any vehicles on alternative fuels.40

Still, the annual turnover rate for heavy-duty trucks is a relevant factor in the pace at 

which a shift to natural gas is likely to penetrate the heavy-duty sector. The high turnover 

rate for heavy-duty trucks means that steady demand for new trucks could be a 

facilitating factor to the development of a natural gas network for heavy-duty fueling. 

The market for new heavy-duty trucks in the coming years will be substantial. Between 

2014 and 2025 roughly 2.7 million new trucks will be purchased – or 76% of the total 

fleet in 2025, creating a ready market for natural gas vehicles, if commercial incentives 

are evident.

Building on work by the US National Petroleum Council (2012), our independent 

assessment shows that the cost benefit of natural gas as a direct fuel is most compelling

 

40 Alt Fuels: Beyond Natural gas. Fleet Owner Magazine. April 8, 2014. 

http://fleetowner.com/running-green/alt-fuels-beyond-natural-gas
31

for heavy truck fleets whose vehicles travel 120,000 miles a year or more, given a diesel 

price of $4/gallon, $2.45/dge for LNG, and $2.34/dge for CNG41. We find that greater 

use of natural gas in the heavy-duty sector could potentially lower the cost of U.S. freight 

supply chains and thereby enhance U.S. competitiveness and energy security. In 

particular, we find that while natural gas vehicles can be more expensive upfront than

conventional diesel powered medium- and heavy-duty vehicles, the fuel savings can 

produce attractive payback for natural gas fleet owners in less than three years.

The breakeven fuel prices for LNG and CNG are shown in Table 2 for the various truck 

designs. The results indicate that, from a fuel cost perspective, CNG is more favorable 

than LNG, but the range of CNG vehicles is much shorter than LNG vehicles. From the 

engine perspective, the economics of the CI dual fuel engine is more favorable using 

either CNG or LNG even though the CI engine is initially more expensive. 

Table 2. Breakeven fuel prices for NGVs by technology/storage configuration and 

payback period based on total annual mileage.

Vehicle 2 yr./120k miles 3 yr./60k miles 3 yr./160k miles

LNG-Ci (dual fuel) $2.60 $1.80 $3.20

LNG-Si $2.21 $1.85 $2.60

CNG-Ci (dual fuel) $3.50 $3.20 $3.80

CNG-Si $3.00 $2.80 $3.30

The results in Table 2 indicate that trucks with an annual mileage greater than 120,000

miles traveled per year provide a favorable payback period for a shift to natural gas of 

less than three years. Note that the base price of diesel fuel for this calculation was 

$4/gallon. If the breakeven price is greater than the price of the fuel, the economics of 

that case is favorable. Trucks travelling more than 120,000 miles per year are responsible 

for just over 38% of the all truck miles in the United States.

At present, most fleets that are considering LNG fuel are looking at the trucks with the Si

engine, which is less expensive than the dual-fuel compressed ignition engine (with a 

diesel pilot) (i.e. HPDI model). The advantage of the HPDI truck is that the vehicle 

operates at similar efficiency as a diesel engine even adjusting for energy content 

differences between the two fuels. Even though the more efficient HPDI engine would 

provide better economic and environmental performance, there is a disconnect between 

the public policy and economic objectives of a fuel switch. Right now, the dual-fuel 

engine is not commercially available in large numbers and it sells at a premium price. We 

believe that this barrier would have to be eliminated for key states, such as California, to 

embrace natural gas as a direct fuel. The manufacturer of the dual fuel engine, Westport, 

 

41 Zhao H, Burke A, and Zhu L. Analysis of Class 8 Hybrid-Electric Truck Technologies Using Diesel, LNG, 

Electricity, and Hydrogen as the Fuel for Various Applications. EVS27. Barcelona, Spain. November 17-20, 2013. For 

other industry-based background on the issue, see The National Petroleum Council (2012), Advancing Technology for 

America’s Transportation Future: Fuel and Vehicle Systems Analyses: Natural Gas Analysis. 
32

has so far not announced any immediate plans to mass produce it. Westport Cummins, a 

50-50 joint venture between Westport and Cummins, is the manufacturer of most of the 

Si natural gas engines. With a Si truck, the driver needs to refuel more often, which costs

time, or requires larger storage capacity, which reduces cargo space. In terms of fuel 

storage, CNG systems are also less costly than LNG systems. But natural gas as CNG has 

lower energy density, thus for a given range, a NGV will require more storage space if 

using CNG than if using LNG. Costs for storage units and other components are expected 

to be reduced over time, as more industry players enter the market in the U.S. and China. 

CNG trucks are generally less expensive than LNG trucks but at present are only 

available with the less efficient Si engines. Both lower energy density and lower engine 

efficiency contribute to making CNG fueled vehicles require even more frequent 

refueling than LNG trucks. The CNG refueling process is also more time consuming than 

LNG refueling. This means that, for long trips, the added initial cost for the LNG HPDI 

technology provides a more attractive long run payback than the higher operating costs of 

operating based on a CNG vehicle once downtimes are taken into account. This is 

another reason the Ci engine will become attractive if/when it becomes commercially 

available.

Infrastructure Modeling Approach 

To analyze the potential for an expansion of natural gas into the heavy-duty sector and its 

widespread use across the country’s major trucking routes, we take into consideration the 

barriers and constraints described above and consider the incentives that must exist or be 

created in order to propel natural gas as a key fuel in the U.S. freight system. To study the 

conditions under which either LNG or CNG fuel could be commercial in U.S. long haul 

trucking, we create a modeling framework that utilizes spatial mapping of existing major 

Interstate highways, trucking routes, key fueling routes for fleets and heavy-duty trucks, 

and fueling infrastructure for CNG for fleet operation and LNG for long-haul trucks to 

make infrastructure planning decisions. Spatial network theory and network analysis is 

utilized to generate all of the spatial information that is needed to calculate the most 

profitable trucking corridors to establish LNG infrastructure.42

Our spatial optimization model is designed to determine the most profitable

transportation networks and locations for natural gas flows into transportation markets in 

California and nationally using spatial infrastructure data and comparing costs for 

transportation of natural gas by source, distribution method, and other market 

development variables through mathematical optimization. Our modeling work builds on a 

 

42 Allen Lee, 2014. Locating LNG Refueling Stations for US Freight Trucks Using a Flow-Based, Range Limited 

Facility Location Model integrated with GIS and Supply-Chain Optimization. Transportation Research Board. National 

Academies. January 2014 
33

body of academic literature undertaken in the study of hydrogen fueling in the United States and 

only very limited study of the long haul duty NGV market. 

43

We compare the economics of natural gas transportation from supply site to refueling 

stations either via pipeline or truck, using data on existing natural gas pipelines and 

transmission systems and highway system to determine through the model solution the 

most profitable locations of refueling facilities. This comprehensive assessment tool is 

aimed to simulate the potential volumetric capacity for the natural gas transportation 

market in the United States, as well as optimal location of new and existing fueling 

facilities.

Our study considers where and when infrastructure should be deployed over a 20-year 

time horizon in order to satisfy demand along major trucking routes or corridors. To 

address both spatial and temporal dynamics, we develop a multistage mixed-integer 

linear programming model to optimize the process of building and operating LNG 

liquefaction and distribution facilities. We consider both transitions to using more LNG 

in the heavy-duty vehicle sector or alternatively to build a mix LNG infrastructure and 

CNG refueling networks that would compete against the incumbent fuel, diesel, in high 

volume markets. For more details about our methodology, please see the appendix to this 

paper. 

Modeling Results and Policy Analysis 

Base case scenario

To date, despite the strongest market for commercial truck sales in almost a decade and a 

historic gap between low natural gas prices and high oil prices, America’s natural gas 

highway is struggling to take hold.

44 Our analysis confirms this trend and finds that only 

 

43 As discussed by Dagdougui, the approaches for planning and designing the hydrogen supply chain can be classified 

as follows: 1) optimization methods (most prominent); 2) geographic information systems (GIS) based methods; and 3) 

scenario dependent transition models43. There are a small number of studies that combine the strengths of a national 

energy system optimization approach with a spatially explicit infrastructure optimization approach. Stachan et al. 

described an integrated approach linking spatial GIS modeling of hydrogen infrastructures with an economy-wide 

energy systems (MARKAL) model’s supply and demand43. Parker et al. used an annualized profit maximization 

formulation to study the optimal distribution network for bio-waste to hydrogen43. Previous research on natural gas as 

an alternative fuel has often focused on evaluating the cost effectiveness of natural gas to achieving environmental 

goals in transportation.Yeh provides a review of several national markets. This literature has focused mainly on light 

duty, transit and refuse vehicles applications, while only a few include long haul trucking applications. Rood Werpy 

concludes that high costs, limited refueling infrastructure, and uncertain environmental performance constitute barriers 

to widespread adoption of natural gas as a transportation fuel in the US43 but, in another substantial contribution to the 

literature, Krupnick finds that the move from a long-haul route structure to a “hub and spoke” structure could facilitate 

the development of natural gas refueling infrastructure in the highway system.

44 Bob Tita “Slow Going for Natural Gas Powered Trucks” The Wall Street Journal, August 25, 2014
34

certain regional markets have sufficient traffic density in combination with higher diesel 

prices compared to the U.S. national average to give investors a sufficient return on 

capital to incentivize station construction without government intervention. 

Our regional analysis, under 0.2% LNG market penetration, shows that California and the 

U.S. Great Lakes/Northeast regions, which have a relatively high level of demand and 

traffic density, have the greatest commercial potential at present and could play a key role 

in the network development, as shown in Figure 12.

Figure 12. Dynamic LNG station buildout scenarios under a 0.2% market 

penetration.

The following diagrams show the optimal network build-out for California under today’s 

penetration rate of 0.1%, or where about 6,000 LNG trucks would be in operation across 

the United States. A detailed map of the California build-out network is found in Figure 

13.

Figure 13. Trucking route deployment across the under current 0.1% market 

penetration.

Our results indicate (Figure 14) that for the California network to operate profitably 

under the optimal configuration, conventional station technology of the smallest capacity 

should be deployed. 
35

Figure 14. Dynamic LNG station build out scenarios under 0.1% market 

penetration.

The regional analysis contrasts with the outlook for a national network. At today’s level 

of market penetration of only 0.1% of the heavy-duty trucking fleet operating on LNG 

fuel, investors are unlikely to see a large enough fuel switchover to earn a commercial 

12% return on capital in building a significant national LNG truck-fueling network until 

the year 2030. Our analysis finds that the majority of natural gas fueling stations along 

U.S. Interstate routes would be unprofitable if built under current market conditions (see 

appendix for detailed analysis). 

In summary, the natural gas cost advantage at present is not sufficiently large enough to 

launch a national network based on commercial market forces. Rather, we find that it 

would take roughly 15 years for fuel demand to rise sufficiently and additional 

technological learning to take hold before lower station equipment costs and higher rates 

of trucking demand would support construction of a comprehensive American natural gas 

highway. Although a network of LNG stations is currently in place in several locations, 

our analysis would suggest that many of those stations will have difficulty sustaining 

profitable operations. 

The Potential Role of California as a Regional Launching Base for a National Network

We also tested whether the more profitable regional networks, such as the one in 

California, could lay the groundwork for expansion over time to a more comprehensive 

national network. Our results indicate that support for regional pilot programs in 

California and/or the Great Lakes region would hasten the development of America’s 

natural gas highway and lower the cost of implementation in the long run. 

Figure 15 shows the price difference for each built station for California. Notice that still 

not all stations are potentially profitable, but as long as the routes as a whole are making 

profit, the profits from highly desirable locations will offset losses at stations 

experiencing less traffic, allowing the entire route to receive a 12% rate of return on 

capital. As discussed above, the lower volume stations are necessary to ensure trucks 

have sufficient coverage to travel the entire route and use only LNG fuel. 
36

Figure 15. Dynamic LNG station price difference per diesel gallon equivalent under 

0.1% market penetration.

California is a unique investment opportunity because it has a solitary main trucking 

artery that means truckers do not have the desire to branch out into alternative routings. 

This limits the number of stations that need to be provided to ensure that truckers have 

the full coverage needed to use LNG vehicles. We calculate that the costs to provide 

dedicated coverage for LNG across California are relatively low at under $100 million, 

were the number of LNG trucks on the road in the United States to double from 3,000 

currently to 6,000. More specifically, it would cost roughly $10 million to construct all 

the LNG stations show in Figure 15 in our model year 2012, and roughly $80 million to 

construct all the micro-LNG liquefaction plants in Figure 16 in our model year 2012. 

Given this result, it is surprising that integrated oil companies do not see such a network 

as a profitable way to comply with California’s Low Carbon Fuel Standard. 

Figure 16. LNG liquefaction plant build out scenarios under 0.1% market 

penetration.

California already has several LNG fueling stations, including two at the Port of Long

Beach. The California example demonstrates that station investors should be looking first 

and foremost for high volume routes where truckers have fewer routing options than in 

other parts of the country. It also confirms the corporate strategy being undertaken by 

fuel providers and truck manufacturers to focus marketing efforts on large corporate 

fleets where a couple of large early adopters could make a limited route such as 

California’s I-5 a commercially viable, cost-effective place to introduce LNG as an 

alternative fuel. We find that comparable investments in the U.S. Mid-Continent would 

not pan out as commercially attractive without substantially higher initial investment 
37

levels. To launch a successful national network of LNG stations, where the industry 

would be making profit as a whole, would be prohibitively expensive in the billions of

dollars, far more than might be reasonably considered by the federal government or a 

small number of commercial investors. 

Our analysis would suggest that companies should first establish limited networks in 

California and the Great Lakes region in making investments in natural gas fueling 

infrastructure because these regions offer the highest potential concentration of fleets’

adoption that could realistically direct a sufficient number of trucks to create a profitable 

network of stations. Eventually, a natural gas station network could extend beyond these

initial LNG hotspot markets. The concept that a handful of large fleets could commit to 

substantial purchases of LNG trucks in a particular regional market finds evidence in 

today’s commercial climate. For example, UPS ordered about 700 natural gas tractors in 

2013, showing the viability of getting adoption of the additional trucks via a fleets 

purchasing model. A California network receives an extra financial boost from the 

existence of a liquid carbon pollution market that qualifies credits for natural gas fuel use.

Alternative Scenarios

To test the sensitivity of the profitability of a national network to the number of trucks on 

the road, we analyze a scenario where double the current number of trucks would be 

operating with LNG fuel. We compare our modeling results against four case study 

scenarios: 1) a 50% subsidy to station costs (or the equivalent of a 50% cost 

breakthrough) under current levels of demand; 2) a 50% subsidy to station costs (or the 

equivalent of a 50% cost breakthrough) under 100% higher levels of demand than 

currently seen; 3) a high diesel price scenario where regional diesel prices are at peak 

levels seen in 2008; 4) a high diesel price scenario where regional diesel prices are at 

peak levels seen in 2008 and under conditions of 100% higher demand than currently 

seen. Table 3 summarizes our results.
38

Table 3. Summary of Results by Scenario.

0.1% Initial Penetration Rate 0.2% Initial Penetration Rate

Summary

Route 

Completion 

2015

Route 

Completion 

2030

Summary

Route 

Completion 

2015

Route 

Completion 

2030

No 

Subsidy

Network 

only builds 

in California.

0% 2%

Network begins in 

California and 

extends Eastward. 

Northeast and Great 

Lakes regions begin 

construction in 

2025.

3% 55%

50% 

Subsidy

Network 

begins in 

California 

and extends 

eastward.

2% 6%

Network begins 

construction in 

California, Arizona 

and Nevada. 

Construction in the 

Great Lakes begins 

in 2015.

28% 76%

High 

Diesel

Network 

begins in 

California 

and extends 

eastward.

0% 6%

Network begins in 

California. East and 

West coasts 

connected in 2015.

69% 77%

We discuss these scenario results in more detail below: 

Alternative Scenario 1: U.S. Natural Gas Fueling Networks Under a Doubling of 

LNG Trucks

To test the sensitivity of the profitability of a national network to the number of trucks on 

the road, we analyze a scenario where double the current number of trucks would be 

operating with LNG fuel. Figure 17 shows the location and configuration of LNG 

refueling network. Figure 18 shows the distribution of profitable stations over time under 

a 0.02% market penetration case. Not surprisingly, optimum station build-out patterns 

favor the regions with higher heavy trucking traffic flows (California, Midwest and the 

Great Lakes routes (Wisconsin-Illinois region, Kansas City region, Nashville, 

Dayton/Cincinnati, upstate New York) as well as areas with high diesel prices (California, 

New York, Ohio, and the Mid-Atlantic). Figure 19 (plants) micro LNG liquefaction 

plants also show strong favoritism in California, Midwest, and Mid-Atlantic/New 

England areas.

Figure 18 shows the respective price differentials by station and there appears to be a 

direct correlation between high station densities regions, like the ones described above 

and competitive LNG prices when compared with diesel prices. High volume routes in 
39

Texas and Florida lag other regions as early adopters. In the case of Texas, low diesel 

prices may be a contributing factor. Florida lacks a high volume route into the state, 

despite a large flow of traffic exiting from its ports. 

Figure 17. Dynamic LNG station build out scenario under 0.2% market penetration.

Figure 18. Dynamic LNG station price difference per diesel gallon equivalent under 

0.2% market penetration.

Figure 19. LNG liquefaction plant build out scenarios under 0.2% market 

penetration.
40

Figure 20. Trucking route deployment under 0.2% market penetration.

California’s heavy density of both liquefaction plants and LNG stations can potentially 

serve as a launching point for a broader network of stations over time. Figures 17-20 

reveal our results for how the network might develop based on solely commercial factors 

over time, starting in California under the 0.02% scenario where the market contains 

6,000 LNG trucks in operation. 

Our results reveal some interesting commercial dynamics to the temporal aspects to 

technology choices. Conventional technology is highly favored over small-scale, modular 

LNG technology small-scale modular LNG technology as can be seen in Figure 17. This 

is mainly due to the very high upfront cost of the LNG box technology but also because 

some conventional stations and liquefaction plants are partially financed already. In this 

process, early on, micro-LNG plants, which provide an economy of scale benefit to fuel 

providers, are built near these high demand seeded areas and remain concentrated in these 

areas even in later years. In order for small-scale, modular LNG technology to be 

competitive with conventional stations, they will require a faster technology learning rate 

or a subsidy.

Alternative Scenario 2: Subsidy Scenarios

Using a case study approach, we study what level of investment is needed to get past the 

chicken-and-egg problem of station coverage sufficiently that new investment becomes 

sustainably profitable. Under current market conditions, we find that it is unlikely that 

national policy intervention of federal truck subsidies or federal station subsidies would 

be cost effective. 

On a national basis, investors would have to be willing to build substantial facilities at a 

loss until those facilities reached a market concentration of over 2% to 3% of market 

share even under a scenario where they receive a 50% subsidy on station costs. Such a 
41

subsidy would be prohibitively expensive, in the billions of dollars. A core element of 

this result is the capital intensity of new fueling station investments which have to 

compete against sales outlets of incumbent fuels whose distribution networks are fully 

depreciated. In effect, natural gas’ price discount would have to be large enough to cover 

both the high capital costs for building out new stations and higher operating costs for 

LNG fuel. 

We do not find this result surprising because an alternative fuels station adoption cost gap 

exists between fuel/system operations costs for incumbent ample diesel stations that are 

already amortized, and the high cost of new LNG fueling infrastructure. Figure 21 

demonstrates the large cost advantage the existing diesel fueling system has over LNG, 

even with the large discount in the underlying natural gas as compared to diesel fuel 

prices. 

Figure 21. LNG delivered cost by station flow volume.

To date, U.S. states that have implemented programs to support natural gas as a transport 

fuel have provided incentives or subsidies either on vehicle purchases or retrofits or on 

station costs. 

Figure 22 shows the range of policies used to stimulate natural gas vehicles in the United 

States. A number of states are offering incentives to support the expansion of natural gas 

as a transportation fuel. Pennsylvania, home to the rich Marcellus Shale gas basin, 

recently announced the Natural Gas Development Program that would provide $20 

million over three years to convert or acquire heavy-duty vehicles that run on CNG and 
42

tailored the Alternative Fuel Infrastructure Grant to support mid duty vehicles conversion 

and fueling infrastructure financing through the Alternative and Clean Energy Fund. The 

state of Oklahoma, in another example, instituted a 75% subsidy on CNG fueling stations 

in 2012 as part of its goal to facilitate the use of natural gas in commercial vehicles.

Figure 22 provides a view of available state incentives.

Figure 22. State incentives applicable to natural gas vehicles. 45

Station Subsidy Scenario Results

When we test the robustness of our results against a 50% discount on the cost for LNG 

fueling stations, we find that only the profitability of a California network is greatly 

enhanced, with almost all stations in the state yielding a positive margin greater than 

$1.00. The results indicate that the carbon credit currently provided to natural gas fuel 

under California’s current climate policies should be helpful in enabling a commercially 

profitable natural gas network in the state. The analysis also shows that a 50% subsidy 

would allow a large expansion of LNG liquefaction plants after 2025 as cumulative 

demand accrues over time. 

A 50% reduction in station costs is not sufficient for the modeling solution to result in a 

build-out of a national LNG network in the next few years, indicating that the existing 

station costs for either traditional or small-scale, modular LNG technology are 

 

45 Westport.
43

prohibitively expensive to allow investors to realize a typical rate of return on capital of 

12% given limitations on the speed to gear up LNG truck demand.

Truck Subsidy Scenario Results

We also consider an intervention where either the cost of natural gas fuel trucks falls 

dramatically or government subsidizes truck purchases. There is some indication that 

natural gas fuel truck tanks manufactured in China could cost up to 60% to 70% less than 

those currently manufactured in North America. We find that a doubling of the current 

penetration rates for LNG trucks can have significant impacts on future LNG network 

development. These results mimic reality and support the suggestion that policy 

intervention will be needed to get a national LNG network off the ground. The familiar 

question of whether it is more effective to reduce station prices or support higher LNG 

truck demand by subsidizing the vehicles is debatable. Our analysis suggests either 

option could influence market development. Directionally, scenarios analysis indicates

that the market might be slightly more sensitive to a lowering of truck acquisition costs 

than to station construction costs since our scenario analysis indicates that a doubling of 

existing truck penetration rates would have a larger impact on network expansion than a 

50% station cost subsidy.

Our scenarios also show that policy choices could influence the competition between 

LNG supply technologies. Generally speaking, in the early stages of natural gas fueling 

network buildout, conventional technology of plant and traditional fueling station 

technology is the least cost technology for early infrastructure implementation. Since the 

static model incorporates existing infrastructure, the network build out from regions that 

benefit from the highest densities such as California, Texas, the Midwest, and East Coast 

with stations connecting east and west. As penetration rates rise, the number and sizes of 

stations also increases in these locations but new stations emerge in other markets as well, 

notably Florida. The Mid-Continent remains less dense but routes become more abundant 

with greater station connections between the U.S. East and West Coasts. LNG modular 

technology starts to be deployed on high traffic routes, mainly in California, once the 

network gets to 3% concentration, as shown in Figure 23.
44

Figure 23. Static LNG station build out scenarios.

Figure 24 depicts the location build-out for micro-LNG plants under various rates of 

market penetration. The main visible difference in the 50% subsidy scenario is that smallscale, modular LNG technology gets built much earlier on, suggesting that the higher cost 

of that technology is a barrier and lowering its costs would enable the network to build 

faster.46

Figure 24. Static LNG plant build out scenarios.

Alternative Scenario 3: High Oil Price Scenario

U.S. diesel prices are currently declining as supply surpluses in global markets have put 

pressure on oil prices overall. But geopolitical factors could reverse this trend, raising the 

possibility that someday higher oil prices could potentially enhance the profitability of 

 

46 The reason the subsidy favors LNG box technology is that small-scale, modular LNG technology does not require an 

intermediate step. It directly converts gas to liquid, whereas the conventional pathway requires additional unsubsidized 

infrastructure (i.e. a liquefaction plant for conversion). In other words, the entire LNG pathway is contained inside a 

small scale modular technology, but a conventional station is only one component of its pathway. Thus, when smallscale, modular LNG technology gets a 50% reduction, it reduces the cost of the entire pathway but when a conventional 

station gets a 50% subsidy, its pathway is only partially subsidized. Components of the conventional pathway like the 

liquefaction plants and trucking costs are not factored in, only the capital deployed towards the stations gets the 

advantage of the subsidy so the percentage of the system capital that is subsidized is lower than the 50% enjoyed by 

each modular small scale unit. Thus, despite economies of scale for conventional technology, a 50% station subsidy 

favors small-scale, modular LNG technology development.
45

LNG as a trucking fuel. Using the modeling simulation, we test whether an increase in 

diesel prices while natural gas prices remain constant would be a sufficient condition to 

propel a higher level of station network construction. We find that even at higher oil 

prices, which creates a wider differential between the fuels is still not sufficient to 

overcome the alternative fuels adoption cost gap and seed initial development of an entire 

national network for natural gas fueling. 

But under the high diesel price scenario and a U.S. fleet of 6,000 trucks (i.e. double 

today’s level) price differential density plots for this scenario reveal stronger impetus for 

network development and coverage, notably in Texas and Florida, when compared to 

other scenarios. This high oil price scenario also results in a notably strong 

transcontinental density of stations connecting the eastern United States with the west. 

High Oil Price Scenario Results

Our analysis indicates that significantly higher diesel prices in certain states creates an 

adequate threshold to promote broader LNG adoption in key hotspot locations, whereas a 

50% station subsidy scenario results in a more sparsely populated network that is 

stretched too thinly across the nation. Under the high diesel, 6,000 truck penetration rate 

scenario, local hotspots develop regionally and eventually expand to nearby regions, 

which initially aren’t experiencing as much development. Figure 25 (build-out, 0.2%) 

also suggests some very interesting station technology implications. Under the no subsidy, 

high diesel scenario, small-scale, modular LNG technology fills in network connections 

in the U.S. Mid-Continent (Heartland & Mountain regions) since overall traffic volumes 

are lower, and therefore don’t support the scale economies of a larger scale hub and 

spoke mini-LNG plant infrastructure system.

Figure 25. Dynamic LNG refueling station build out scenarios under 0.2% LNG 

market penetration rate.
46

Figure 26. Dynamic liquefaction plant build out scenarios under 0.2% market 

penetration rate.

Figure 27. Dynamic LNG-Diesel price spread under 0.2% LNG market penetration 

($/gde)

CNG as an Alternative to LNG Fuel 

We test our results against a scenario where CNG stations are available as an alternative 

technology. Because CNG technology is less expensive on a supply chain per gallon 

basis than LNG and it can be built profitably at smaller scales, we find that CNG 

becomes an enabling technology in the development of broader natural gas fueling 

infrastructure. CNG stations can be profitable at smaller sizes than LNG and can 

supplement LNG networks with LCNG (liquefied-compressed natural gas) optionality to 

help station owners optimize revenue streams from access to natural gas feedstock. 

Figure 28 shows how CNG quickly becomes a competing technology to LNG in long 

distance trucking at the 0.2% market penetration scenario as demand for natural gas fuel 

develops in California and beyond, especially under scenarios where station subsidies are 

offered or diesel prices are high. 
47

Figure 28. Dynamic CNG and LNG station build out under 0.2% market 

penetration rate.

Our results suggest that to best promote an alternative fuel into heavy-duty trucking, such 

as LNG, focus should begin on the highest volume freight routes such as California and 

the upper Midwest and then eventually commercial factors will encourage investment to 

branch out to other hotspot regions such as the Mid-Atlantic. 

Our findings have interesting implications for California where fuel providers can earn 

carbon pollution credits under the LCFS and cap and trade systems. We find that if LNG 

could get to a limited penetration of 0.2% of the heavy trucking market, a commercial 

network in California could get off the ground. A subsidy in the form of carbon credits 

(natural gas currently is valued at a 20% savings to diesel under the LCFS) will help this 

process along. The state of California is currently investigating whether a build-out of 

natural gas fueling infrastructure across the state would facilitate higher use of renewable 

biogas as a low carbon transport fuel. Our initial analysis would confirm that this 

pathway may prove viable if the state’s network of natural gas fueling infrastructure 

could reach a minimum threshold. Another source of LNG fuel could come from LNG 

export terminals built in the northern United States to export natural gas to Asia. We do 

not consider this source of LNG fuel for this study but it could be a subject of future 

research. However, as will be discussed at length below, technological and process 

improvements for the natural gas supply chain would have to be made for fossil natural 

gas to meet California’s long term climate goals as a low carbon fuel. 
48

Business Models for Advancing Natural Gas in Transportation 

Business Model A

Private companies Clean Energy Fuels and ENN have begun building commercial fueling 

stations for LNG and CNG for use in long distance trucking. The business model for 

these stations is to seed the network with a minimum number of cross-country stations 

while simultaneously soliciting large trucking fleet owners and operators to switch a 

portion of their operations to natural gas fuel. 

Clean Energy is the largest natural gas fuel provider in North America with over 330 

natural gas fueling stations, serving 660 fleets and 25,000 vehicles. The company 

currently sells an average of 200 million gallons a year of CNG and LNG. Clean Energy 

says it is able to achieve a return to capital for fueling station investment and still pass on 

$1.00 to $1.50 a gallon in fuel savings to customers. The company’s business model is to 

line up with return-to-base segment shipping for LNG fuel. In its presentations, Clean 

Energy says it engaged with trucking companies to determine optimal station locations; 

however, not all stations currently in operation are profitable and the momentum for its 

America’s Natural Gas Highway has slowed some in the last year.47

Clean Energy’s initial efforts received some support from Oklahoma Gov. Mary Fallin’s 

initiative to promote natural gas in transportation in the state and beyond. To promote the 

use of natural gas in transportation, Oklahoma brought together original equipment

manufacturers (OEMs), station providers and natural gas producers to create a 

coordinated effort that would overcome chicken and egg infrastructure issues, at least for 

CNG networks in the state. The state orchestrated bulk government purchasing orders of 

natural gas vehicles from the major automakers at a discounted level while offering a 

75% station cost subsidy to station developers in exchange for a commitment to construct 

a credible number of fueling stations. There are currently close to 30 natural gas fueling 

stations in Oklahoma. 

By the same token, ENN also has begun its efforts in Utah, which similarly had a statesponsored program to enhance the use of natural gas vehicles. In February 2009, then 

Gov. Jon Huntsman announced that Utah would increase the state’s NGV fueling 

infrastructure,48 the state offered incentives to drivers to offset the higher price for the 

NGV vehicle and Questar offered financing and lease programs to customers to support 

the economics of the conversions. As a result, Utah has 99 natural gas fueling stations, 

public and private, many of which are located along primary highway corridors to 

support the fuel requirements of heavy-duty trucks. 

Several national fleets are deploying natural gas trucks, including: Cisco, Pepsi, Walmart, 

Frito-Lay, HEB, Trimac Transportation, Truck Tire Service Corporation (TTS), Verizon, 

 

47 Bob Tita “Slow Going for Natural Gas Powered Trucks” The Wall Street Journal, August 25, 2014

48 Press Release, Office of the Governor of Utah, February 12, 2009
49

UPS, AT&T, Food Lion, and Ryder. One consideration for fleet truck owners is that 

vehicle turnover typically takes place within five years, at which time trucks are then sold 

to secondary and tertiary markets in the United States and Mexico. The economics of 

conversion to natural gas must therefore take into account resale value of the vehicle as 

well as lower operating costs but current rapid paybacks and the gradual emergence of 

buyers in the secondary market is driving more companies to consider natural gas fuel. 

Fleet owners also worry that supply chains for natural gas vehicles are not yet sufficiently 

high to avoid higher maintenance costs than traditional diesel vehicles and knowledge of 

the vehicle among trained maintenance workers is also lower, again potentially leading to 

higher fixed operating costs. Finally, fleet managers remain concerned that the gap 

between oil and natural gas prices will not remain at currently wide levels, adding an 

element of price risk. 

While there have been some instances of local and state governments providing subsidies 

for trucking fleet owners to shift to natural gas vehicles, it seems unlikely that sufficient 

public funds into the billions of dollars will become available to offer incentives to truck 

owners to create sufficient demand to get the national long-distance natural gas fueling 

infrastructure to a tipping point. Instead, natural gas marketers may have to consider 

alternative business models such as the utilization of derivatives and swaps instruments. 

At present, the oil–natural gas differential available on futures markets averages $9.50-

$9.57/mmBTU from one year forward to three years forward. The eight-year long-range 

differential indicates natural gas is $9.18/mmBTU cheaper. Under swap arrangements, a 

financial intermediary could offer fleet owners a financial contract that locks in the 

purchase of the spread between natural gas and oil that is currently available in derivative 

markets. At the same time, the intermediary can offload the risk of the contract through 

an equal and opposite sale of the spread to a natural gas producer, who might be 

concerned that natural gas prices will fall relative to oil over time if surpluses continue to 

develop in North America and globally. By engaging in a swap arrangement, the fleet 

owner can guarantee that the margins needed to ensure the payback for a shift to natural 

gas vehicles are sustainable even if the price of oil were to fall over time. 
50

Figure 29. LNG price swap process.

Business model B.

Another business model is for LNG providers to consider parallel investments in LNG 

for ships as an anchor to create demand that would support investment in LNG trucking 

infrastructure emanating in ports and expanding beyond them. One critical driver toward 

LNG adoption could come from the regulations which designate emission control areas 

(ECAs). ECAs regulate the emissions of sulfur and nitrogen oxides. Over time these 

regulations will become stricter requiring alternatives to the present fueling systems. In 

addition the ECA regulations specify varying emissions requirements depending on the 

distance from certain shorelines. The North American ECA specifies stricter emissions 

limits within 200 nautical miles of the shoreline. Given the strict North American ECA, 

some shipping companies are investigating adopting LNG for shipping trips that spend a 

significant amount of time near the North American shore, such as trips from the Los 

Angeles region to Seattle or Alaska. The Port of Tacoma will soon lease land to build an 

LNG bunkering facility. The Totem Ocean Trailer Express Company operates ships 

between the Tacoma and Alaska posts and plans to retrofit 2 ships for LNG operation. 

The decision was driven by the ECA requirements.

However, the cost to either purchase new LNG ships or retrofit ships to LNG is 

significant. Given the long turnover rates, typically 30 years or longer, relatively few 

ships require replacement at any given time. The same chicken-and-egg issue relevant to 

LNG trucks acts as a barrier for LNG shipping adoption. Both LNG bunkering terminals 

and ships must be installed or purchased to make the decision to adopt LNG (see 

LNG

PRODUCER

LNG

END-USER

SWAP 

DEALER

PHYSICAL LNG MARKET

Payment =

Quantity × Index Price

Payment =

Quantity × Fixed Price

Payment =

Quantity × Fixed Price

Payment =

Quantity × Index Price

RECEIVE

FLOATING

MARKET

PRICE

SELL

LNG

PAY

FLOATING

MARKET

PRICE

BUY

LNG

PRODUCER PRICE HEDGE CONSUMER PRICE HEDGE

LNG PRICE SWAP
51

appendix for additional discussion of costs for alternative means of compliance). Thus, 

like trucking, there are many uncertainties about the pace and scale of marine adoption of 

LNG fuel, making it difficult for investors to rely on port demand to serve a major anchor 

for developing the U.S. natural gas heavy-duty network system over the next five to ten 

year time frame.

Environmental Performance Analysis

As discussed, natural gas can provide benefits as a trucking fuel in terms of fuel costs and 

energy security. It has also been shown to play a substantive role in limiting certain kinds 

of air pollutants. For the California market, fuels are also judged by their carbon intensity 

and currently natural gas qualifies as a low carbon fuel under the LCFS for light-duty 

vehicles. For heavy-duty applications, the carbon intensity of natural gas as a fuel varies 

depending on drive cycle, engine efficiency and distribution system equipment. 

In this section we discuss particulate matter, oxides of nitrogen (NOx) and carbon 

emissions

Particulate matter and Nitrogen Oxides

Particulate matter

EPA estimates that heavy-duty vehicles currently contribute more than 60% of the total 

particulate matter (PM) emissions from on-road vehicles. Mobile emissions themselves 

constitute 4 and 6% of the total PM2.5 and PM10 emissions, respectively, in the US. In 

California, mobile sources constitute 21% of total PM2.5 and 40% of total PM1049. 

According to California Air Resources Board (ARB) diesel engines and equipment rank 

as the 8th and 9th highest contributors50 to PM2.5. State regulation requires diesel trucks 

and buses that operate in California to be upgraded to reduce emissions, and to be 

completely replaced by 2010 or later models progressively between 2015 and 2023. The 

regulation applies to nearly all privately and federally-owned diesel fueled trucks and 

buses and to privately and publicly owned school buses with a gross vehicle weight rating 

(GVWR) greater than 14,000 pounds1.

In diesel technology, particulate matter is effectively controlled with filters, but filters, 

like any other emission control devices add cost and require maintenance. A shift to 

natural gas is an alternative to installing filters because natural gas fuel typically emits

less PM and sufur oxides (SOx, which are PM precursors) than diesel without 

aftertreatment. A shift to LNG fuel can contribute a significant reduction in SOx tailpipe 

 

49 State and County Emission Summaries

http://www.epa.gov/cgibin/broker?_service=data&_debug=0&_program=dataprog.state_1.sas&pol=PM25_PRI&stfips=06

50Amendments Approved in April 2014 http://www.arb.ca.gov/msprog/onrdiesel/onrdiesel.htm
52

emissions as well as an almost a full-scale elimination in fine particulate matter in heavyduty trucks. Regions with heavy use of diesel and bunker fuel (marine ECAS, ports, 

industrial sites, and roads with dense heavy-truck traffic or other non-attainment areas 

where diesel is heavily used) can achieve substantial air quality improvements by 

switching to natural gas-based fuel. 

However, the scientific literature also suggests that engine type, aftertreatment 

technology, idling patterns, and drive cycle are more important than the type of fuel used, 

and thus this must also be taken into account for California to garner the optimum air 

quality benefits from a shift to natural gas in heavy-duty trucking. For example, diesel 

engines with particulate filters could produce lower levels of particulates than natural gas 

engines not equipped with aftertreatment technologies, but when NGVs are equipped 

with three-way catalyst technology, they produce generally much lower particulate and 

NOx emissions than do older NGVs without updated technology51.

Nitrogen oxides

On-road mobile sources is the top contributor to NOx in the U.S.

52 In California, heavyduty vehicles contribute to more than 30% of all nitrogen oxide (NOx) emissions from 

on-road vehicles53. NOx is an ozone precursor. The San Joaquin Valley and the South 

Coast air basins in California both surpass the federal ozone standard of 75 parts per 

billion (ppb)

54. Heavy-duty on-road diesel vehicles are the largest source of NOx 

emissions in both these areas.

55 NOx emissions from heavy-duty trucks are limited 

federally to 0.2 grams NOx per brake horsepower-hour (bhp) for model years 2010 and 

later. 

A 2009 survey of heavy-duty truck drivers at points of entry into California showed that 

non-California-registered trucks concentrated in the air basis that were having air quality 

issues56. Thus, the regulation applied to all trucks that operate in California even if they 

are not registered in California.

Strategies to comply with NOx standards include the use of alternative fuels. Biodiesel, 

blends of diesel with fuels made from plant oils, animal fats and waste oils have gained 

some attention, but studies find combustion of biodiesel blends results in slightly higher 

 

51 Yoon S, Collins J, Thiruvengadaem A, Gautam M, Herner J, Ayala, A, (2013) “Criteria pollutant and greenhouse gas 

emissions from CNG transit buses equipped with three-way catalysts compared to lean-burn engines and oxidation 

catalyst technologies, Journal of Air Waste Management Association, 63 (8) 926-33; Also Chandler, Eberts, Melendez, 

(2006) finds roughly 20 to 25 percent greenhouse gas emissions reductions for CNG transit buses compared to diesel in 

2004 engine models.

52EPA. Part III Environmental Protection Agency 40 CFR Parts 50 and 58 Primary National Ambient Air Quality 

Standards for Nitrogen Dioxide; Tuesday, February 9, 2010

Final Rule. Federal Register http://www.epa.gov/ttn/naaqs/standards/nox/fr/20100209.pdf

53 Facts About On-Road Heavy-Duty Vehicle Programs http://www.arb.ca.gov/enf/hdvip/onroad_hdtruck_factsheet.pdf

54 http://www.epa.gov/air/criteria.html

55

 Sokolsky S, Silver F, Pitkanen W. “Heavy-duty truck and bus natural gas vehicle technology roadmap”. July 2014.

56 Lutsey N. Assessment of out-of-state truck activity in California. Transport Policy Volume 16, Issue 1, January 2009, 

Pages 12–18
53

NOx emissions than combustion of ultra-low sulfur diesel (ULSF), with variability across 

the different engine models tested57. Natural gas can also be used as alternative fuel for 

trucks. Academic studies generally agree that natural gas engines can achieve lower 

emissions than diesel trucks of the same efficiency primarily due to fundamental fuel 

properties and in-cylinder combustion modifications58. For example, in a study at West 

Virginia University (WVU) on trucks using a portable heavy-duty chassis dynamometer,

LNG trucks averaged 80% less NOx emissions, but reductions varied across natural gas 

engine manufacturers

59

. The WVU portable laboratory was also used to test trucks and 

buses using Caterpillar dual fuel natural gas (DFNG) engines; it also found reduced NOx 

but the extent of NOx reduction was dependent on the type of test cycle used60.

Despite efforts, NOx attainment in the California basins is proving evasive. CARB

adopted in December 2013 optional ultra-low nitrogen oxides (NOx) emission standards 

for diesel truck engines, with funding opportunities are available via programs such as the 

Carl Moyer Program61. Under these new optional rules, there are three new levels of

optional certification corresponding to reductions respect to the current federal standard 

of 50%, 75%, and 90% (i.e., 0.1 g/hp-hr, 0.05 g/hp-hr, and 0.02 g/hp-hr respectively). 

Natural gas blended with hydrogen could meet the more restrictive NOx levels, even 

without aftertreatment, according to engine dynamometer tests at the University of 

Central Florida/Florida Solar Energy Center on and Sandia National Laboratories 62.

Other studies find that natural gas without aftertreatment has less ability to control NOx 

pollution63.

NOx formation is maximized at peak temperature in diesel engines. A strategy to reduce 

NOx consists of introducing cooled exhaust gas that is also lower in oxygen reducing the 

production of NOx. However, the lower temperature produces less effective combustion 

and thus more CO2 and PM (and more fuel consumption). Exhaust gas recirculation 

(EGR) systems can be combined with particulate filters to control PM emissions, but 

increased CO2 will still occur. Thus, there is the concern that NOx goals can hinder 

efforts for fuel economy improvement in what it is sometimes referred as the NOx-GHG 

 

57Venkata NG. 2010 Exhaust emissions analysis for ultra low sulfur diesel and biodiesel garbage truck. Master’s 

Thesis. The University of Toledo 

58Korakianitis T, Namasivayam A.M., Crookes R.J. “Natural-gas fueled spark-ignition (SI) and compression-ignition 

(CI) engine performance and emissions. Progress in Energy and Combustion Science

Volume 37, Issue 1, February 2011, Pages 89–112

59 Weaver, C., Turner, S., Balam-Almanza, M., and Gable, R., "Comparison of In-Use Emissions from Diesel and 

Natural Gas Trucks and Buses," SAE Technical Paper 2000-01-3473, 2000, doi:10.4271/2000-01-3473.

60 Norton, P., Frailey, M., Clark, N., Lyons, D. et al., "Chassis Dynamometer Emission Measurements from Trucks and 

Buses using Dual-Fuel Natural Gas Engines," SAE Technical Paper 1999-01-3525, 1999, doi:10.4271/1999-01-3525.

61 http://www.arb.ca.gov/msprog/onrdiesel/onrdiesel.htm

62 Hoekstra, R., Van Blarigan, P., and Mulligan, N., "NOx Emissions and Efficiency of Hydrogen, Natural Gas, and 

Hydrogen/Natural Gas Blended Fuels," SAE Technical Paper 961103, 1996, doi:10.4271/961103.

63 Yoon S, Collins J, Thiruvengadaem A, Gautam M, Herner J, Ayala, A, (2013) “Criteria pollutant and greenhouse gas 

emissions from CNG transit buses equipped with three-way catalysts compared to lean-burn engines and oxidation 

catalyst technologies, Journal of Air Waste Management Association, 63 (8) 926-33; Also Chandler, Eberts, Melendez, 

(2006) finds roughly 20 to 25 percent greenhouse gas emissions reductions for CNG transit buses compared to diesel in 

2004 engine models. 
54

tradeoff. Older garbage trucks were found to emit more NOx and SOx but less CO and 

CO2 than newer trucks. A NOx-PM tradeoff also exists. 

An alternative to EGR is using selective catalytic reduction (SCR). A more optimal 

engine timing can be procured for reduced PM emissions, but this will produce higher 

engine out NOx. In this case, optimal timing controls PM and an SCR reduces NOx. With 

this mechanism both the NOx-PM and the NOx-GHG tradeoffs are largely solved and 

actually allowed fuel economy to improve in newer diesel engines64. ARB found that 

SCRs realized reductions of 75% NOx reductions during cruise and transient modes, but 

no NOx reductions during idle65. This could be due to the fact that catalysts require at 

least 200°C before significant NOx reduction is achieved. This temperature is not 

maintained right after engine start, during idling or even at low speeds,

66thus possibly 

explaining why real emissions have been found higher than predicted by emissions 

models used in certifications 67 , 68 . It is becoming clear to regulators that operating 

parameters such as coolant temperature, fuel temperature, percent fuel, engine speed are

important in determining exhaust emissions in trucks. Vehicle model, age, aftertreatment 

technology, and driving cycle can be as or more relevant factor than fuel type (ie natural 

gas or diesel) used in determining NOx emissions.69

One challenge for NOx regulation for both natural gas and diesel trucks is that NOx 

control technology can produce a fuel efficiency penalty thus emits more carbon and the 

new EPA/NHTSA CAFÉ-like regulations for trucks 70 requires more aggressive fuel 

economy. Advances in turbocharging technology, such as inertia reduction, aerodynamics 

 

64 Personal communication with ARB staff.

65Dinh Herner J., Hu S., Robertson W.H., Huai T., Collins J.F., Dwyer J.F., and Ayala A. “Effect of Advanced 

Aftertreatment for PM and NOx Control on Heavy-Duty Diesel Truck Emissions” Environ. Sci. 

Technol., 2009, 43 (15), pp 5928–5933”

66 Venkata NG. 2010 Exhaust emissions analysis for ultra low sulfur diesel and biodiesel garbage truck. Masters 

Thesis. The University of Toledo

67 Weaver, C., Turner, S., Balam-Almanza, M., and Gable, R., "Comparison of In-Use Emissions from Diesel and 

Natural Gas Trucks and Buses," SAE Technical Paper 2000-01-3473, 2000, doi:10.4271/2000-01-3473.

68 http://researchplanning.arb.wagn.org/files/Activity_Data_HDD_SOW-20666.pdf

69 Idling regulations restrict trucks from idling more than five minutes or idling in school zones and some technologies 

such as an auxiliary power unit (APU) or direct-fired heater (DFH) can be used to increase temperature and reduce 

NOx emissions at idling. APU and DFH have been shown to reduce NOx by 89% and 99% respectively. Emissions 

tests from Class 8 over-the-road tractors on a chassis dynamometer showed emissions from Idle and Creep Modes were 

found to be variable due to varying auxiliary loads on the engine, according to Air Resources Board-sponsored truck 

activity programs. Engine control unit (ECU) or on board data (OBD) loggers can help with maintenance, but more 

importantly they could be used to improve characterization of certification models. CalHEAT Truck Research Center 

at CALSTART in a roadmap prepared for The Southern California Gas Company suggests optional ultra-low NOx 

standards could focus on emission reduction technologies problem areas, such as thermal management of NOx 

emission reduction technologies. Characterize heavy-duty truck activity profiles (e.g., duty cycles, starts and soak time) 

for different vocational uses to identify operating conditions relevant to SCR function. Evaluate emission test cycles to 

represent SCR relevant operating modes. Post-combustion after-treatment technology such as optimized catalysts and 

improved conversion efficiencies, can be employed on natural gas engines to further reduce emissions of NOx and CO2. 

July 2014 Heavy duty truck and bus natural gas vehicle technology roadmap, Prepared by Steven Sokolsky, Fred 

Silver, and Whitney Pitkanen.

70 EPA/NHTSA CAFÉ standards for trucks: Phase 1 (10-23% reduction in fuel consumption required model year 2014-

2018) and Phase 2, which will be announced 2015, will be more stringent.
55

and bearing improvements- and other technologies71 relevant to both natural gas and 

diesel engines-could be applicable72. As it is shown below, increasing fuel economy is a 

key strategy in order to make natural gas trucks less carbon intensive.

Greenhouse gases

In terms of climate pollution, tailpipe emissions from burning natural gas in heavy-duty

trucking applications will produce between two-thirds and three-fourths the emissions of

burning gasoline or diesel73, but there are other issues that affect the well-to-wheels 

carbon intensity of natural gas in transportation. The variables that impact the 

environmental performance of natural gas include the level of methane and carbon 

dioxide venting and leakage from upstream production (i.e., non-combustion related) and 

the methane and carbon emissions associated with fuel processing (e.g., gas production, 

gas compression or liquefaction, etc.).

According to our analysis with GREET 2014 74and assuming national averages of 

methane leakage75, and in a case where the more efficient HPDI engine is used in LNG 

trucking, system-wide methane leakage from natural gas production and distribution 

cannot exceed 3% for natural gas to break even in carbon intensity (Figure 30). But many 

LNG trucks are equipped with the less efficient spark ignition engine and for this 

circumstance, methane leakage would need to be eliminated entirely for natural gas to 

match the carbon intensity of more efficient diesel engines (Figure 30). 

We also find that the effects of leakage can be more significant for CNG than LNG76.

CNG requires distribution via leaky natural gas local pipelines to the refueling stations 

where it is compressed, whereas LNG is transported as LNG from LNG plant to refueling 

station by truck. For these reasons, no carbon pollution advantage is found compared to 

diesel in cases where NGV trucks are equipped with the less-efficient Si engine 

technology and the more methane leakage-prone CNG. 

 

71 Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: 

First Report. The National Academies Press, Washington, DC 

72 Arnold, S., Balis, C., Jeckel, D., Larcher, S. et al., "Advances in Turbocharging Technology and its Impact on 

Meeting Proposed California GHG Emission Regulations," SAE Technical Paper 2005-01-1852, 2005, 

doi:10.4271/2005-01-1852.

73 Zhao et al. 2013

74 Rood Werpy M., Santitni D., Burnham A., and Mintz M., Argonne National Laboratory “White Paper on Natural 

Gas Vehicle: Status, Barriers, and Opportunities” September 2009 which found that in-use emissions reductions varied 

by region, fuel composition and engine configurations. The authors conclude that light duty natural gas vehicles can 

offer up to a 15 percent reduction in greenhouse gas emissions

75 Dominguez-Faus, R. The Carbon Intensity of C8 NGV trucks. Working paper. 

76 These results are based on national natural gas supply chain assumptions. In California, results can be different due 

the lower leakage in the pipeline infrastructure and the higher energy efficiencies in upstream processes.
56

Figure 30. 100-year carbon intensity (gCO2e/mile) of C8 diesel and natural gas 

under different leakages rate.

Figure 31 compares the contribution in grams of CO2 per mile to the 100 year carbon 

intensity (CI) of diesel and three configurations of NGV Class 8 trucks. This comparison 

reveals that the only vehicle-storage technology combination that would provide a 

beneficial carbon reduction with respect to diesel under the currently accepted 

Environmental Protection Agency (EPA) official methane leakage rate of 1.12%, would 

be the high-efficiency HPDI Ci engine using LNG.
57

Figure 31. Contribution to total carbon intensity of diesel and natural gas C8 trucks 

under current 1.12% leakage rate.

Technologies exist for industry to curb upstream methane leakage significantly. In 2012 

EPA ruled that all new oil and gas wells must use green completions beginning in 2015. 

The rule only applies to existing or modified wells, and affects an estimated 13,000 wells 

every year. While designed to control smog-contributing pollutants, green completions 

are also able to control methane emissions at oil and gas production sites. A study by the 

Environmental Defense Fund (EDF) found that a large number of operators are using

these best practice technologies already.77 According to official estimates, between 2012 

and 2015, when green completions were only voluntary, methane emissions were reduced 

by 16%, despite the increase in oil and gas production. Technologies exist to bring 

wellhead methane leakage to zero. However, these technologies only reduce leakage at 

field operations. Additional technologies will be required to eliminate leaks at processing 

facilities, transmission lines and local distribution pipelines which can often be leakier. 

EPA is now in the process of drafting methane-specific regulations to be issued sometime 

in 2016. The new regulations will apply to new and modified infrastructure, and will 

potentially cover production and distribution operations, not just drilling. According to 

EPA estimates, the new regulations could achieve reductions of methane leaks in natural 

gas and oil systems of 40% to 45% by 2015, using 2012 as baseline.

Still, the largest potential improvements in the carbon intensity of NGVs running on 

fossil natural gas will come from gains in natural gas vehicle efficiency. Even if all 

 

77 http://www.edf.org/methaneleakage; also see A R Brandt et al, (2014) Science Vol 343, “Methane Leaks from 

North American Natural gas systems,” 
58

upstream methane leakage were completely eliminated, NGVs using HPDI engines (5.36 

miles per dge) would provide an 8% reduction in carbon emissions compared to diesel, 

while a Si engine (4.68 miles per dge) would produce only insignificant benefits. Under 

the higher estimates of 3% methane leakage rates, NGVs powered by the more inefficient 

Si engines would create a 40% increase in carbon emissions compared to diesel. Under a 

3% methane leakage situation, NGVs equipped with HPDI engines would still be 20% 

more carbon intensive than the most efficient diesel engine. Carbon intensity of natural 

gas fuel may also be lowered by co-mingling fossil natural gas supplies with lower 

carbon intensity renewable natural gas from bio-waste sources. 

The carbon intensity of NGVs in California is below the national average, leaving more 

leeway for natural gas vehicles to meet the state’s carbon reduction goals. The leakage 

reported in the California pipeline infrastructure is lower than the national average. 

However, a comparative analysis reveals that it is the stringent air quality and energy 

efficiency regulations on stationary sources such as oil recovery and processing which 

contribute to a lower carbon intensity of all fossil transportation fuels in California, as 

those indirectly contribute to higher efficiency and decarbonization of energy used in 

upstream processes. To understand better the differences between California and national 

results, data uncertainties and modeling caveats, see the working paper on carbon 

intensities by Rosa Dominguez-Faus. 78

Our analysis suggests that improving efficiencies in vehicle engine and during upstream 

processes can be more effective at reducing the carbon intensity of natural gas in 

transportation than a strategy based in controlling methane leaks alone. 

Conclusions and Implications for Policy

The deeply entrenched incumbency of oil-based fuels and their well-established 

infrastructure distribution provide a formidable barrier to the transition to alternative 

fuels. Even for a fuel such as LNG, which currently enjoys a deep cost discount to diesel, 

establishing a competitive fueling network will be challenging. Moving LNG into the 

heavy-duty trucking fleet could prove the most pliable of the options for fuel-switching 

based on commercial factors. That is because the turnover rate for Class 8 vehicles is 

fairly rapid compared to other kinds of vehicle stocks (three years, for example,

compared to 10 to 14 years for light-duty vehicles) and vehicle ownership tends to be 

concentrated in large corporate fleets whose vehicles have high miles utilization per year 

and who can scale up more quickly than individual vehicle owners to shift vehicle 

technologies. 

 

78 Rosa Dominguez-Faus working paper, “The Carbon Intensity of C8 NGV Trucks.”
59

But large fleet owners will not be willing to make investments in alternative fuel vehicles 

unless they are assured of dedicated fueling station availability for their entire travel route. 

Thus, our scenario analysis suggests that the best way to promote an alternative fuel, such 

as LNG, into the heavy-duty trucking sector would be to focus initially on the highest 

volume freight routes such as California and the upper Midwest and then eventually 

commercial factors will encourage investment to branch out to other hotspot regions such 

as the Mid-Atlantic.

Trying to build from scratch a well-covered national network is not the most optimal 

approach to establishing a LNG highway, at least in the early stages. Instead, it may be 

beneficial to first establish limited networks in California or the Great Lakes region 

because these regions could benefit most from a high concentration of fleets adoption to 

add realistically a sufficient number of trucks to create a profitable network of stations. 

Eventually, a natural gas station network could extend beyond this initial LNG hotspot 

market. 

Conceptually, focusing on a handful of large fleets that could commit to substantial 

purchases of LNG trucks in a particular regional market makes commercial sense and is 

consistent with the current commercial climate. For example, UPS ordered about 700 

natural gas tractors in 2013 alone, showing the viability of getting adoption of the 

additional trucks via a fleets purchasing model. 

Policy makers at the federal level have expressed an interest in promoting natural gas as a 

transport fuel in commercial fleets as a means to promote energy security, given abundant, 

domestic natural gas supplies that are located in geographically diverse locations. North 

American natural gas fuel is also expected to remain less expensive than oil-based fuel, 

opening the possibility of more cost-effective supply chains that can better compete with 

international markets. Finally, a push for natural gas into transportation will ensure that 

domestic producers have a ready domestic market for their gas to prevent supply 

overhangs from threatening profitability and associated job growth. However, to best 

utilize natural gas into U.S. trucking, policy makers need to consider both commercial 

realities in the market as well as ways to improve the environmental performance of 

natural gas as a direct fuel. 

Successful public-private partnerships have already been utilized in some U.S. states such 

as Oklahoma to promote a switch to CNG vehicles for government work fleets. Policy 

makers can consider whether a pilot project federal-state partnership for LNG trucking 

could benefit the U.S. natural gas industry while at the same time promoting alternative 

fuel goals. The United States’ recent commitment to reduce greenhouse gas emissions 

25% to 28% from 2005 levels by 2030 includes stringent regulation of methane 

emissions, venting and flaring from U.S. domestic oil and gas production. Any shift to 

natural gas fuel would have to be considered in this context. 
60

The question of what hotspot to select for a pilot project for natural gas vehicles is a 

complicated one. Our analysis would suggest that high access to natural gas supplies is 

less important than the density of freight miles traveled on local highways. Optimum 

station build-out patterns favor the regions with higher heavy trucking traffic flows 

(California and the Great Lakes routes (Wisconsin-Illinois region, Kansas City Region, 

Nashville, Dayton/Cincinnati, upstate New York) as well as areas with high diesel prices 

(California, New York, Ohio, and the Mid-Atlantic). Small scale micro LNG liquefaction 

plants also show strong favoritism in California, Midwest, and Mid-Atlantic/New 

England areas.

At present, the California natural gas heavy-duty trucking network receives an extra 

financial boost from the existence of a liquid carbon pollution market that qualifies 

credits for natural gas fuel use. California currently offers fuel providers carbon pollution 

credits under the LCFS and cap and trade systems. We find that if LNG could get to a 

limited penetration of 0.2% of the heavy trucking market, a commercial network in 

California could get off the ground. A subsidy in the form of carbon credits (fossil natural 

gas currently has a 20% lower carbon score than diesel under the LCFS) will help this 

process along. But the California Air Resources Board is considering regulations that will 

lower the credit available to natural gas fuel. Our environmental modeling suggests that 

this is justified based on updated analysis on methane leakage along the natural gas value 

chain together with efficiency penalties for typical Si natural gas engines. For LNG to 

meet California’s goals for reducing the carbon footprint of fuels used by vehicles in the 

state, costs for advanced engine technologies such as the HDPI engine will need to fall 

further and carbon intensity of both vehicles and natural gas production and distribution 

infrastructure will need to be improved. 

Still, interest in natural gas as a trucking fuel should not be rejected out of hand as the

state of California is also investigating whether a build-out of natural gas fueling 

infrastructure across the state would facilitate higher use of renewable biogas as a low 

carbon transport fuel. Our initial analysis would confirm that this pathway may prove 

viable if the state’s network of natural gas fueling stations could reach a minimum 

threshold. 

Several companies are currently investing in natural gas fueling infrastructure in the state 

of California, and there are many major commercial fleets that are operating in the state 

and could profitably switch to natural gas or biogas fuels. This starting base means that 

the cost of building an optimal natural gas fueling system in the state is relatively 

inexpensive compared to the cost of building fueling infrastructure for some of the other 

alternative fuels. 

Since the commercial costs are low for a federal/state collaboration promoting a publicprivate partnership that would utilize natural gas and low carbon biogas fuel in California, 

the development of a natural gas fueling network there could support the expansion of 

natural gas as a fuel in other contiguous markets over time and eventually support the 
61

build-out of a national natural gas network across the U.S. highway system. This would 

suggest that federal government support for California’s efforts to build alternative fuels 

infrastructure would be justifiable as a means to promote domestic natural gas markets in 

the short term and to enable a faster transition to low carbon biogas over the longer run.

Participating station investors could be expected to achieve a rate of return to capital of 

12%, making the network commercially sustainable once built. The experience of the 

state of Oklahoma with natural gas fueling is instructive. The state brought parties 

together simultaneously to organize orders for the vehicles and commitments to build the 

fueling infrastructure under a single initiative receiving some state funding and calibrated 

so that stations and vehicle purchases appeared simultaneously. 

The construction of natural gas infrastructure would be enabling to biogas producers who 

would be assured that fueling networks would be available to commercialize their 

production. California and neighboring states have a biogas resource base that is large 

enough to support between 10,000 and 30,000 LNG trucks, but further study is needed to 

determine what distant resources could be developed and imported profitably from other 

states and nearby countries. The California Biomass Collaborative, a University of 

California Davis-led public-private partnership for the promotion of California biomass 

industries, estimates that 32.5 million billion dry tons (bdt) of in-state biomass feedstocks 

could be available for conversion to useful energy79 In particular, estimates for methane 

production from landfill gas are 55 bcf/year, 4.8 bcf/year for waste water biogas, and 14.6 

bcf/year for biogas from manure sources. Similar biomass resources are located in states 

that border California or are along routes for the transmission of natural gas to the state 

from major producing states. 

We estimate that the methane potential from landfill gas in the Western states outside of 

California is 105 bcf/year based on existing and candidate landfills identified by the

EPA.

80 Parker estimates an additional 100 million bdt/year of lignocellulosic biomass in 

the Western states which are roughly equivalent on an energy-content basis to the 

gasoline used by 14.5 million passenger cars a year. However, some of these in-state and 

external biomass sources are already committed to or could be used for the production of 

liquid biofuels or for dedicated power generation services to the businesses where they 

are co-located81. 

Other states besides California might be amenable to a pilot program for LNG trucking 

but many locations that have already embarked on limited investments such as Utah 

 

79 Williams, R. B., Gildart, M., & Jenkins, B. M. (2008). An Assessment of Biomass Resources in California, 2007. 

CEC PIER Contract50001016: California Biomass Collaborative., (http://biomass.ucdavis.edu/files/reports/2008-cbcresource-assessment.pdf)

80 “Landfill Methane Outreach Program: Energy Projects and Candidate Landfills.” US EPA, 

(http://www.epa.gov/lmop/projects-candidates/index.html)

81 Parker, Nathan, Peter Tittmann, Quinn Hart, Richard Nelson, Ken Skog, Anneliese Schmidt, Edward Gray, and 

Bryan Jenkins. “Development of a biorefinery optimized biofuel supply curve for the Western United States.” Biomass 

and Bioenergy (2010) (34), pp 1597-1607.
62

might find it difficult to promote sustainably commercial expansions that will link 

quickly to sufficiently high traffic networks. Thus, as the federal government seeks 

partnerships for natural gas fuel investment, it will want to consider venues such as the 

upper Great Lakes and Mid-Atlantic that also have the potential to contribute biogas 

inputs and also have highly identifiable heavy freight routes that could support a high 

volume trucking fleet for LNG or CNG powered vehicles. 

National or state efforts to work with vehicle manufacturers to promote best in class 

engine efficiency and commitment to production would also be a critical component of 

any successful initiative to promote natural gas adoption into the heavy-duty sector. Such 

an effort needs to be consistent with emerging climate policies that are currently being 

implemented, such as carbon reduction efforts like those in the state of Colorado, which 

is seeking to eliminate methane leakage from oil and gas production, or recently 

announced plans by the White House in January 2015 of a draft federal methane 

regulation by the summer of 2015.