Is Compressed Natural Gas Finally Feasible for Railroad Applications?

Railroads transport goods extremely efficiently, especially in terms of fuel and greenhouse gas emissions. But most locomotives still run on fossil fuels.

Use of cleaner alternatives such as battery-electric or hydrogen requires new locomotives. However, diesel-powered locomotives can be retrofitted to run on natural gas, enabling companies to more cost-effectively reduce GHG emissions without having to retire locomotives that have years of useful life left.

Challenges of natural gas for rail

Storing sufficient quantities of natural gas to deliver locomotives with the required energy for long-haul applications has been difficult to achieve, and safe handling of natural gas poses challenges.

But David Scott, co-founder, president and CEO of CNGmotive, and Pedro Santos, co-founder and CTO, believe CNGmotive has solved those problems.

Launched in 2015, CNGmotive designed a composite fiberglass tank that is lightweight but still robust enough to hold significant amounts of compressed natural gas (CNG), Santos said. 

Conventional tenders can hold less than 2,500 gallons of diesel equivalent, and it takes more than 90 minutes to fill them, according to CNGmotive's website. CNGmotive's CNG tenders can be filled with 5,000 gallons of diesel equivalent in under 45 minutes, and the company has a design for a tender that can hold 9,000 gallons, according to Scott. 

The Frankfort, Illinois-based company's specialized tenders store natural gas at high pressure, let the pressure down using industrial-size equipment and deliver it to the locomotive at a constant pressure. Scott said that locomotives with the ability to run on any type of natural gas can use this CNG tender.

In terms of safety, Santos said the company's tender has a protective structure to survive serious train accidents, and it has even been used as a standard for alternative fuel tenders.

"The combination of being able to do high-density natural gas and composites with the protective safety systems is what enables CNGmotive to deliver a safe solution with CNG, which by itself is the lowest-emissions and lowest-cost method of transporting gas for a locomotive," Santos said.

Cost benefits of CNG

Similar to all modes of freight transportation, railways prioritize lowering costs, maximizing efficiency and making profits. And the fuel used to power locomotives makes up a large portion of operating costs for railways.

"Some 90% of the energy a railroad uses is diesel fuel, … so that's an enormous cost driver," Scott said.

CNG takes much less energy to make than liquefied natural gas or other synthetic fuels, Santos said, and "that relates to a cost element." Natural gas is relatively cheap, and the interest in it is largely due to cost drivers.

Diesel was $3.67 per gallon as of Monday, according to the U.S. Energy Information Administration. Natural gas is not purchased in gallons, but the cost of the CNG energy equivalent of a gallon of diesel fuel is 30 to 40 cents, Scott said.

Once the infrastructure for natural gas at railroad stations is in place and CNG tenders are purchased for refueling, the cost benefits of using CNG to power locomotives could be huge.

"You have to invest in the infrastructure, and then the marginal cost of your fuel is much, much lower than diesel," Santos said.

Infrastructure needs

Every alternative fuel has different infrastructure needs, and David Nahass, board member of CNGmotive and president of Railroad Financial Corp., told FreightWaves that railways can't be converted for all of them.

"We have an interchange system that requires the transition of assets between railroads where you don't have to decouple and recouple assets to allow for those transitions. So when you think about changing the fueling patterns of the North American Class I railroad system, you can't have one railroad with batteries, one railroad with hydrogen and another one dealing with diesel," Nahass said.

To achieve large-scale CNG adoption, wayside natural gas fueling stations, equipment to compress the natural gas, and tenders to store and deliver CNG to locomotives are necessary. 

Once the industry has access to that, adoption of CNG-powered locomotives could be rapid, Scott said.

"Transitioning any notable amount of Class I locomotive capacity running on natural gas will require overcoming several substantial roadblocks. We saw many of the same hurdles a decade ago facing the trucking industry. Fueling infrastructure is costly, and it takes time to build out competitive corridors. New engines are typically much more expensive than diesel counterparts. But despite these headwinds, it's a much more near-term competitive solution than battery-electric or hydrogen," said Tyler Cole, director of carbon intelligence at FreightWaves.

CNG potential in rail

Many locomotives in the market today run on natural gas. A subsidiary of Caterpillar, Progress Rail, has developed direct-injected gas and dynamic gas blending natural gas retrofit kits for its locomotives.

"Retrofit kits are designed to help quickly convert an existing locomotive fleet to natural gas and have a positive impact on natural gas fueling infrastructure decisions. Locomotives tend to have very long service lives, so it was important to target existing fleets for conversion," Edward Cryer, director of engine development at Progress Rail, told FreightWaves.

Cryer said the retrofit kits can work for CNG and LNG tenders, and they include engine modifications, gas piping, methane detectors and heat transfer equipment when applicable.

There was a lot of attention on using LNG for rail, but "the cost of implementing LNG was disappointing," Santos said.

CNGmotive's CNG tender has not been sold commercially yet, but it is ready for demonstration.

CNGmotive was entering the scene and ready for demonstrations when the COVID-19 pandemic hit, according to Santos. He said the added lens of sustainability and companies' goals to reduce emissions could speed up the process. 

"Of all the alternative fuels, natural gas is the only one that has generally a few dozen installations that are actively running," Santos said.

Santos said that hydrogen and battery-electric locomotives have potential to work well for short-distance rail routes. But electric batteries don't have enough energy density for long-haul rail, he said, and many alternative fuels are extremely expensive or require massive infrastructure updates.

Read: Net-Zero Carbon: International Alphabet Soup

How fast could CNG decarbonize rail?

Decarbonization of rail using CNG "could be fairly quick" if incentives and regulations align with it. Santos cited California's success with decarbonizing highway fuels through the low carbon fuel standard as an example.

"The railroad industry produces about 40 million metric tons of carbon dioxide per year, and that's in exhaust emissions from locomotives," Scott said.

Once the infrastructure and equipment are on-site, Scott said, "decarbonization becomes a supply chain decision."

The natural gas pipeline is "ubiquitous," so companies can buy the rights to renewable natural gas (RNG), Scott said, which has a negative carbon footprint. RNG is captured from sites such as landfills and dairy farms that emit methane naturally, so capturing it and using it to fuel a vehicle or locomotive makes it carbon-negative.

"Natural gas is a key part of the energy transition to reducing GHGs. When using natural gas to replace diesel, there is a significant potential to reduce GHGs, particularly if RNG is used," Cryer said.

If accounting is done accurately, companies can have confidence that the GHG reductions achieved by purchasing RNG credits are not claimed by any other parties.

That means companies using CNG could decarbonize their rail activities by purchasing enough RNG to power their locomotives.

Read: Why is reducing emissions in freight so hard?

"Tailwinds for CNGmotive's solution include increased demand from shippers for low-carbon transportation, steadily increasing volumes of RNG (a result of clean fuel policy), newly available engine technologies, and price spikes in diesel," Cole said.

Considering the railroad assets such as locomotives have such long lifespans, "the transition to decarbonization is going to be, reasonably speaking, a 30-year process," Santos said. And testing, development, and adoption would have to start now to get there by 2050.

The availability of RNG "future-proofs" the switch to CNG-powered locomotives, Scott said.

Progress Rail is looking at many alternative fuel options for transportation, and Cryer said railroads are looking for fuels such as biodiesel, renewable diesel, and natural gas that can have a quick impact on GHG emissions and carbon intensity.

"Natural gas presents the most convenient and cost-effective solution to moving to an alternate fuel that has a carbon-neutral potential. There's really no other alternative that has anything that's realistic in time frame and opportunity," Nahass said.

Click here for more FreightWaves articles by Alyssa Sporrer.

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