THE North American railfreight network stretches roughly 225,000km across the continent. But unlike Europe and Russia which rely heavily on electric traction, overhead catenary is almost entirely absent on American freight railways, leaving diesel as the sole fuel source.

Despite aggressively pursuing improvements in fuel consumption in the past 15 years, the Class 1 railways still spend a staggering amount on diesel fuel, an estimated $US 9bn in 2012. And with the price of diesel continuing to rise - it reached an average of $US 0.87 a litre in 2012 - fuel is now the second largest outlay for the Class 1s behind only wages and benefits.

BNSF, which has the second largest network of all the Class 1s, claims that it is the number two diesel consumer in the United States behind the US Navy, while Union Pacific, the largest of the Class 1s says it spent nearly $US 3.5bn in 2012; its trains consumed 5.01 billion litres of fuel at an average cost of $US 0.71 a litre. Norfolk Southern, which operates 33,525km of lines and 4143 diesel locomotives, spent $US 1.58bn.

Efforts to explore alternatives which could help to lower these costs have consequently been stepped up. While trials have taken place with varous bio-diesels, Liquefied Natural Gas (LNG) is the current alternative that is catching the North American railway industry's imagination, particularly given its current $US 0.11 per litre cost at industrial prices.

The price is so low due to the current glut of natural gas in the American market as a result of the shale oil and gas boom. And with government policy emphasising domestic energy production, the railways are optimistic that prices will remain low in the long-term.

There are several methods to deliver LNG fuel to the locomotive prime-mover. All require vaporising LNG, which consists of cryogenic methane chilled to -162oC following the removal of other products including water, butane and propane. This process takes place in the fuel tender, while in the engine's power assemblies (cylinders) diesel fuel, which ignites under high compression, is used to ignite the natural gas.

Technology does not currently exist to inject LNG directly into engine cylinders for combustion. Instead gaseous methane, not LNG, is passed onto the dual-fuel locomotive and into the engine cylinders.

LNGThis method provides some operational flexibility, depending upon the LNG:diesel ratio. High pressure direct injection (HPDI) at 344.7 bar to 551.6 bar and low pressure (8.6 bar) fuel delivery methods are being analysed. HPDI fuel delivery requires port or direct injection at the cylinder and is purported to save anywhere from 40% to 60% in fuel costs.

Currently a 100% LNG locomotive is not under consideration because using LNG requires a spark at the cylinder and existing engines would have to be extensively modified to accommodate spark ignition. LNG also does not ignite under compression.

GE Transportation's LNG technology, which is being developed and tested at its Erie, Pennsylvania, plant, is based on a mix of 80% LNG and 20% diesel using an existing GEVO engine. This ratio allows the engine to revert to 100% diesel in the event of an LNG-related failure or the unavailability of an LNG stationary or mobile refuelling station. Similar trials of 90% LNG/10% diesel are in development. However, a 95% LNG/5% diesel, reverting to 100% diesel is still not possible.

Two forms of fuel tenders are configurable: a 45,500-litre ISO tank, or a 91,000 - 136,500-litre tender that closely resembles a tank car. However, these quantities are not yet established as railways explore the operational requirements for using LNG. Early estimates have shown though that an LNG-powered freight train using 113,750-litre LNG fuel tenders could operate between Los Angeles and Chicago one-way without a refuelling stop.

The ISO LNG tank, though of lower capacity, offers more operational flexibility and potentially lower cost. At 40ft in length and enclosed in a steel frame, the ISO tank can be mounted in a modified double-stack intermodal wagon, and can be easily removed when empty and replaced with a full tank transported by truck, thus eliminating the cost and logistical constraints of a dedicated LNG fuelling station.

For a purpose-built fuel tender, the latest refuelling equipment is projected to provide a refuelling time of 30 to 45 minutes, about 1820 litres per minute, which is longer than a diesel refuelling stop, but required less frequently.

Fuel tender safety is of course a prime consideration. In general, LNG is safer than diesel or gasoline, since it does not ignite in liquid form and in gaseous form LNG will ignite only at around 537oC and in high oxygen concentrations. In addition, if it spills, it vaporises instantly and dissipates, although this is affected by factors such as humidity and wind.

LNG cryogenic tanks, supplied by companies like Chart Industries and Westport Innovations, are also highly crashworthy. They are constructed as a double tank; an inner tank, which is typically stainless steel, although aluminium is sometimes used, is encased in a flexible material, and enclosed in a carbon-steel or stainless steel outer tank. A vacuum is created in the space between the inner and outer tanks.


A series of trials to test these applications is now underway through partnerships between the railways and various suppliers. And while any upgrades will not come cheap - retrofitting a diesel locomotive by adding the tank car could add 50% to its approximate $US 2m pricetag - the potential $US 200,000 savings in fuel costs per locomotive per year, means that widespread adoption is a strong possibility.

BNSF president Mr Matt Rose describes the adoption of LNG as ranking "right up there" with the industry's shift from steam to diesel traction and says that his company will move quickly to retrofit existing locomotives in the next few years if its pilot programme, which commenced this autumn and will take one to two years to complete, proves successful.

BNSF is currently working with Electro-Motive Diesel (EMD) and GE on its pilot, with EMD supplying three locomotives, and an HPDI stationary test reportedly underway.

EMD is also working with Canadian National (CN) on its trial which began in 2012. This has involved rebuilding two EMD SD40-2 2.24MW locomotives equipped with modified 16-645E3 engines. The engines were converted to use 90% LNG and 10% diesel using kits supplied by Energy Conversions (ECI), with LNG stored in a 122,850-litre LNG tender originally built in 1992 for UP and modified specifically for the programme.

Tests began on the 483km line between Edmonton and Fort McMurray in the oil sands region of Alberta in 2012, and will be extended to mainline trials in 2014.

CN is similarly collaborating with EMD, along with fuel tender supplier Westport and Gaz Métro Transport Solutions (GMTS), one of Canada's largest natural gas distributors, to develop a new LNG engine. EMD is providing two SD70M-2 3.2MW locomotives along with technical expertise to install the LNG engine, with components including Westport's HPDI system and natural gas fuel system technologies. GMTS will develop natural gas liquefaction requirements and distribution systems, while a new natural gas tender will be produced by the project partners for line tests which are scheduled to begin next year.

CSX became the latest to join the search for a LNG solution, announcing on November 13 that it is set to commence a pilot programme in 2014.

GE will supply its NextFuel natural gas retrofit kits for CSX which enable existing GE Evolution Series locomotives to operate with dual fuel capabilities and meet US EPA Tier 3 emissions standards. CSX says it will work over the next few months to develop a test plan and secure regulatory concurrence, and that it is working with GE to develop LNG for other classes of locomotives. It expects field trials to commence in 2014.

NS says that it is also examining the possibility of adopting LNG as a locomotive fuel, but at present does not have any plans to purchase LNG locomotives.

"We're looking at the long-term pricing of natural gas vs diesel and balancing that against the huge capital investment needed for LNG locomotives and for the infrastructure to support them," an NS spokesman told IRJ.

The company is though exploring the use of compressed natural gas (CNG) with a project to construct a CNG-powered locomotive at its Juniata locomotive facility underway. The unit is an EMD GP38-2 with the existing engine modified to burn just natural gas (not dual fuel) using an Energy Conversions kit.

"We are using this project as a means to evaluate the feasibility of natural gas as a fuel in railroad operations, and to familiarise ourselves with what it takes to support such equipment," NS says.

Industry standard

While the Class 1s work on implementing their own technical solutions, development of an industry-standard fuel tender is simultaneously taking place.

This is being led by the American Association of Railroads' (AAR) Natural Gas Fuel Tender Technical Advisory Group (NGFT TAG), a joint effort of the AAR's Locomotive, Tank Car and Equipment Engineering Committees, Amtrak, and each of the Class 1s, with personnel support from the AAR and Technology Transportation Centre Inc (TTCI). The group is chaired by Mr Michael Iden, Union Pacific's general director for car and locomotive engineering, and is tackling regulatory and safety issues for adoption of LNG as an alternative locomotive fuel.

For example under current regulations, LNG is not permitted to move by rail unless there is an FRA waiver. The group will consequently consider safety, crashworthiness, and environmental protection standards as well as tender design and construction regulations, tender to locomotive interfaces and connections, tender interoperability, maintainability and development of dual-fuel and gas-fuel locomotives and tenders. It has also met with locomotive and engine as well as freight and tank wagon manufacturers where it is soliciting feedback and providing updates on standards, and is working with the FRA to develop fuel tender performance standards.

"The AAR creates and maintains performance standards for many facets of the railroad industry and is the logical organisation to take on the challenge of creating industry standards that offer homogeneity for fuel tender designs in support of industry and regulatory requirements," Iden says.

"The TAG is also not ruling out the use of CNG and hence the possibility of CNG fuel tenders. However, the majority of the TAG's effort at this time is on LNG fuel tenders as LNG is the logical form of natural gas fuel to support long-distance line-haul locomotives. There are four existing tank-car-style prototype tenders from the 1980s and 1990s and several new yet-to-be-operated well-car style tenders."

Despite the trials and attempts to regulate LNG, adoption appears to be raising more questions than answers at this stage. This is perhaps testament to the enthusiasm from the industry at the proposed use of LNG and how it can realistically be achieved to the benefit of all.

The primary challenges are clearly the capital investment required to upgrade assets and infrastructure to accommodate LNG use, the potential impact on maintenance costs, the logistics of getting LNG to a fuelling site and into the tender wagon, and the possibility of compromising the fuel cost savings by over-investing.

Other significant challenges are the issues regarding integrating dual-fuel locomotives and fuel tenders in an increasingly interconnected network involving freight railroads serving three nations in North America, increasing amounts of run-through trains and locomotives among carriers, and the additional complication of distributed power locomotive consists within freight trains.

Certainly the upfront costs to the US Class 1s are significant and it is unlikely for this reason alone that there will ever be a complete transition from diesel to LNG. It is also heavily reliant on LNG prices remaining low, which is at best difficult, if not impossible to predict over a period of 30 years, the lifespan of a locomotive. It is clear then that diesel will remain an economic fuel source in certain situations. However, the fact the Class 1s are looking at alternative fuel sources is encouraging from an environmental perspective and adoption in some parts could go a long way to reinforce the argument about the resource efficiency of railways in North America.

While making a comparison to the transition from steam to diesel does appears to be a little strong - adopting LNG will not require the same change in physical assets, cost structure, company organisation, maintenance practices and pools of labour which occurred in the middle of the 20th century - it could be a sign of things to come in the battle to remain competitive. This is particularly true as the long-distance trucking industry in the United States also looks at how it can utilise LNG to its advantage.