King of the road for decades when it comes to powering trucks, diesel will not easily nor soon fall from its throne despite the inroads alternative fuels are making into its territory.

There are both near- and long-term reasons to argue that the alternative voted most likely to succeed diesel— natural gas in its two fuel forms—will fall short of fully marginalizing diesel’s role in trucking.Indeed, regardless of what alternative fuels exist now or will in the future, why diesel has been so effective for so long as a truck fuel cannot be discounted.

“Diesel is the standard by which other fuels are judged,” remarks Ed Saxman, Volvo Trucks’ marketing product manager for alternative fuels. “Even at today’s prices, it comes at a reasonable cost, it’s widely available, and it’s easy to fuel with, even on the side of the road. “It’s also clean,” he adds.

“Diesel engines that are EPA 2010-certified have reduced all regulated pollutants in their exhaust by 99%. That’s a true accomplishment and it sets a high bar for alternative fuels, all of which also need aftertreatment of some sort to meet the same emissions limits.” “Diesel fuel can be thought of as one of the original alternative fuels,” points out Jennifer Rumsey, Cummins’ vice president-Midrange & Heavy Duty Engineering.

“Diesel’s widespread availability along major transportation corridors, the ease with which it can be stored and dispensed, and its performance characteristics mean that it continues to be an attractive fuel option for fleets. “Diesel fuel’s low flammability makes it a safe fuel source and allows it to be stored easily both in dispenser tanks and onboard vehicles without having to incorporate sophisticated safety precautions,” she continues. “These benefits extend beyond storage into other areas such as fuel handling and hauling as well as engine service.”

Rumsey notes that the “infrastructure required to support diesel-fueled vehicles, especially over-the-road trucks, is mature with widespread availability of diesel fuel along all major transportation corridors.

“Engines operating on diesel fuel have demonstrated capability to provide high power density and torque as well as being very durable,” she adds. “In addition, diesel fuel offers exceptional fuel economy.”

As David McKenna, Mack Trucks’ director of powertrain sales & marketing, sees it, over a century after it was invented “the diesel engine remains pure genius—no other internal-combustion engine comes close to its efficiency. And with the emissions changes, it’s very hard to beat diesel when looking at net cost of operation. It has the advantage over other fuels in fueling and maintenance/repair infrastructure as well as tech training.”

ROOM AT THE TABLE

He also says diesel’s power density vs. other fuels is significant, providing for greater range. “There’s a lot more energy in a gallon of diesel than an equivalent gallon of natural gas. It depends on the duty cycle, but a truck can consume two to three times as much natural gas to get the same energy content as diesel delivers.

“There’s room at the table for both natural gas and [other] alternative fuels,” McKenna adds. “But diesel does remain a fantastic deal overall. And keep in mind that a lot of the shale production we hear about results in diesel being refined as well as natural gas.”

Speaking of natural gas, the widespread adoption of liquefied natural gas (LNG) engines to power long-haul tractors is being stymied by issues that in all likelihood will eventually be worked out. But it’s impossible to wager how soon that will happen—or whether the endplay will be fully embraced by fleet owners.

Further out, three key factors will influence how successful natural gas is vs. diesel as an over-the-road truck fuel. The first involves aspects of federal energy and environmental policy that could benefit diesel. The second is how natural gas fuel prices here may be driven up by greater exportation resulting from the boom in shale-gas production. The third concerns the negative picture currently presented by the full carbon footprint of LNG as well as that of compressed natural gas (CNG) vehicle fuels.

Despite the substantial fuel-savings potential of running natural gas vehicles (NGVs), right now—and into the foreseeable future—many fleet owners are understandably wary about switching to them from diesel power.

The obstacles to immediate NGV adoption are multiple: the initial price premium ($40,000 to $80,000 more than diesel by some estimates); that no market exists yet for used NGVs; the substantial costs to install dedicated maintenance facilities and on-site fueling stations (mainly for CNG); ongoing higher maintenance costs (estimated to be as much as two cents more per mile); and the lack to date of sufficient on-highway fueling infrastructure for LNG-fueled trucks.

“The most significant obstacles to LNG are the enormous purchase price premium associated with a natural gas truck compared to an equivalent diesel truck and the lack of a competitive LNG refueling infrastructure,” points out the American Trucking Assns. (ATA) in a statement it prepared for the U.S. Senate’s Energy & Natural Resources Committee.

“If Congress enacts financial incentives to ensure that the price of an LNG truck is equivalent to a diesel truck and that cost-effective LNG refueling facilities can be constructed, then LNG trucks may be a viable alternative for the small segment of the [over-the-road trucking] industry that is centrally refueled,” according to ATA.

GREEN SIDE

And in a position paper on alternative fuels, ATA observes, on the other hand, that due to its lower energy density, “CNG is not practical for long-distance, heavy-duty truck applications. CNG is being successfully used in shorter range, heavy-duty applications such as refuse trucks, concrete mixers, straight trucks and municipal buses.”

“Because of diesel’s unmatched energy density, efficiency, performance and existing [fueling] infrastructure, there is no near-term substitute for diesel” as the “primary fuel for heavy-duty transportation and construction and agricultural machinery in this role,” contends the Diesel Technology Forum (DTF) in a paper titled “Diesel: Fueling the Future in a Green Economy.”

According to DTF, the introduction of advanced engine and fuel technology as well as renewable fuel capabilities, meaning biodiesel, will allow diesel to “continue its traditional role” as well as expand into new market sectors.

“The future direction of climate, energy and environmental policies in the U.S. is toward increased efficiency, reduced reliance on imported oil, expansion of renewable fuel use, and lower CO2 emissions,” states the diesel advocacy group. “Diesel offers energy and environmental improvement without the need for development of an infrastructure to support the advanced technology”… and its “unique capability to utilize a range of renewable fuels and blends enhances its desirability under emerging [federal] renewable fuel requirements.”

As DTF sees it, the joint EPA-DOT directive to increase the fuel efficiency and decrease the greenhouse gas (GHG) emissions of medium- and heavy-duty trucks for model years 2014 to 2018 “can maximize the use of existing infrastructure for diesel fuel and maintain the functionality of these vehicles to service manufacturers, businesses and consumers.”

One of the key policy strategies to reduce GHG emissions and reliance on imported oil is to use more domestically produced fuel from a variety of plant and biomass feedstocks, points out DTF, noting that diesel’s “unique compression ignition cycle and operating characteristics are highly suitable” for operation with renewable fuels from various feedstocks.

“Most new and existing diesel vehicles and equipment are compatible with lower level biodiesel or renewable diesel fuel blends (5% to 20% depending on manufacturer warranties),” the advocacy group adds. “Compliance with production quality standards and ASTM fuel standards will be critical to greater acceptance and successful use of these fuels in diesel engines.”

As to whether or not natural gas will ever lose its pump-price advantage over diesel, a recent survey report jointly released by RBC Capital Markets and The Economist Intelligence Unit suggests that indeed it could if the exportation of natural gas from the U.S. becomes lucrative enough.

According to RBC, the survey of 357 North American C-suite (those with CEO/COO/CFO titles) executives in a variety of industries revealed that 87% of those polled predict natural gas prices will stay the same or increase over the next two years.

But 73% anticipate a price increase of 10% or more in the next five years. What’s more, 54% of the executives surveyed expect that shale-gas production here could lead to natural gas becoming a significant U.S. export in the medium term.

“Fuel has become the trucking industry’s second largest expense behind labor costs, and management teams are looking for stability and predictability in fuel costs,” points out RBC transport & logistics analyst John Barnes.

“However,” he continues, “there is currently a big push to export as much [natural gas] as possible from the U.S., so it is still uncertain what impact shale discoveries [for production of natural gas] will have on medium- to longer-term fuel prices.”

FINAL FACTOR

The final factor that could help keep diesel on top of the heap is a key aspect of the carbon footprint left by the use of natural gas fuels. For unknown reasons, this issue has not—yet anyway—been acted upon by environmental regulators.

Alan J. Krupnick, senior fellow & director- Center for Energy Economics & Policy for the Washington, DC-based nonprofit research firm Resources for the Future (RFF), writing in RFF’s quarterly Resources magazine, argues succinctly that the obstacle remaining to wide adoption of LNG-fueled trucks is their “uncertain” environmental benefit.

“With [fuel] costs and [fueling] infrastructure in their favor, LNG trucks face one more hurdle—their carbon footprint,” he contends. “Compared to diesel fuel’s lifecycle carbon emissions, those of LNG from conventional gas wells or from shale gas wells are smaller. But if the natural gas itself— methane [CH4]—is not burned, it becomes a greenhouse gas 25 times more powerful than carbon dioxide over a 100-year period in the atmosphere.”

Krupnick does allow that calculating just how methane emissions compare with their carbon dioxide counterparts is tricky. He explains that because methane lasts for far less time in the atmosphere, some researchers use a much higher factor in converting methane to its carbon dioxide equivalent.

“In addition,” says Krupnick, “the amount of methane that escapes—‘fugitive,’ in industry parlance—from gas wells is uncertain. According to the latest studies, putting together the short lifetime of methane and a high estimate for fugitive methane emissions can result in lifecycle emissions for LNG vehicles exceeding those of diesel. Until this issue is settled, the environmental benefits of natural gas vehicles are uncertain.”

Jason Mathers, senior manager of corporate partnerships program for the Environmental Defense Fund (EDF), says that while there are good reasons to be excited about the positive impact of natural gas for trucking, significant concerns remain including the threat of those fugitive methane emissions from NGVs and from the natural gas fuel supply chain as well.

METHANE LEAKAGE

As defined by EDF, methane is the main ingredient in natural gas and a GHG pollutant “many times more potent than carbon dioxide, the principal contributor to man-made climate change. Even small amounts of methane leakage across the natural gas supply chain can undermine the climate benefit of switching to natural gas from other fossil fuels for some period of time.”

A paper co-authored by five scientists titled “Greater Focus Need on Methane Leakage from Natural Gas Infrastructure” published last year in the Proceedings of the National Academy of Sciences concludes “there is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.”

The scientists come down hard on the truly long range impact of methane leakage. “Given EPA’s current estimates of CH4 leakage from natural gas production and delivery infrastructure, in addition to a modest CH4 contribution from the vehicle itself (for which few empirical data are available), CNG-fueled vehicles are not a viable mitigation strategy for climate change. Converting a fleet of gasoline cars to CNG increases radiative forcing [which causes climate change] for 80 years before any net climate benefits are achieved; the comparable cross-over point for heavy-duty diesel vehicles is nearly 300 years.

“Stated differently,” the authors continue, “converting a fleet of cars from gasoline to CNG would result in numerous decades of more rapid climate change because of greater radiative forcing in the early years after the conversion. This is eventually offset by a modest benefit. After 150 years, a CNG fleet would have produced about 10% less cumulative radiative forcing than a gasoline fleet—a benefit equivalent to a fuel economy improvement of 3 mpg in a 30 mpg fleet. CNG vehicles fare even less favorably in comparison to heavy-duty diesel vehicles.”

According to EDF, whose scientists contributed to the National Academy of Sciences’ paper, the study found that methane leak rates would need to be brought below 1% of the gas produced “to ensure that switching from diesel to natural gas produces climate benefits at all points in time… Estimates based on fuel cycle models created by Argonne National Laboratory indicate the production and use of natural gas in transportation can reduce GHG emissions by 13% when compared with burning diesel fuel— if no fugitive methane emissions leak out from the system during the production, transport or use of natural gas.”

Steve Hamburg, chief scientist at EDF, points out that the environmental advocacy group is working with leading researchers and a range of companies on a series of studies aimed at better understanding the methane leak rate across the supply chain. Sponsors of the study include the American Gas Assn., Cummins Westport, Westport Innovations, Volvo Group, Shell Oil, PepsiCo and Waste Management.

“Currently, there is no empirical data on methane leaks associated with natural gas vehicles, only estimates,” stresses Hamburg. “To fully understand the scope of the matter, and what the opportunity is to minimize methane emissions during the operation and refueling of natural gas vehicles, hard data is needed.” EDF aims to wrap up this two-year research effort by this December.

Addressing the issue of methane leakage is extremely crucial, per EDF, as the “trucking industry could be on the verge of a significant migration to natural gas vehicles. By 2020, 40% of new Class 7 and 8 trucks sold could run on natural gas.”

STILL KING

There’s yet another reason to believe diesel will remain a fuel to bank on for decades to come. Though still a nascent trend, global oil/chemical producers are building gas-to-liquids (GTL) plants that can convert natural gas to diesel fuel as well as to gasoline, kerosene and sundry chemicals.

This development is being driven primarily by the wide price spread between diesel and natural gas as a vehicle fuel in many markets, including North America. GTL plants convert natural gas to diesel fuel by way of technology that has evolved since being first developed by German scientists back in the 1920s. Still, despite the glut of natural gas fueling the prospects for GTL, the economics are considered quite challenging.

For that very reason, William Colton, ExxonMobil’s vice president of corporate strategic planning, told The New York Times that “we do not see it [GTL] being a relevant source of fuels over the next 20 years.”

Nonetheless, South Africa-based energy and chemicals firm Sasol Inc. has stated that by 2018 it will have completed the first phase of such a facility near Lake Charles, LA. The firm said its GTL plant will be the first in the U.S. and will turn out 4 million tons a year, or 96,000 barrels a day, of “high-quality transportation fuel, including GTL diesel.”

Sift through all the factors and it’s clear King Diesel won’t wind up parked on the side of the road for decades yet to come.