Assessing Alt-Fuel Options: Hydrogen, RNG or Renewable Diesel?
Alternative fuels appeal to utility fleets largely because they release fewer emissions and typically cost less than traditional gasoline and diesel. But with numerous options available, how do fleet professionals determine the best fit for their operations?
To answer that question, UFP reached out to several subject matter experts, who shared their take on three options: hydrogen gas, renewable natural gas and renewable diesel.
Fuel Production
The U.S. Department of Energy cites “natural gas reforming (a thermal process), and electrolysis” as the two prevailing approaches to hydrogen gas production. “Other methods include solar-driven and biological processes” (see www.energy.gov/cmei/fuels/hydrogen-fuel-basics). While hydrogen can fuel internal combustion engines, it is more commonly used to power fuel cell electric vehicles, with water as the only exhaust. Further, “hydrogen fueling happens independent of the grid, so fleet operations don’t compete with customer demand for power,” explained Luke Wentlent, Ph.D., vice president of product and technology for Plug Power (www.plugpower.com).
Renewable natural gas (RNG) production, which depends on biogas released from decomposing organic waste, is “unique in that it takes an environmental liability – methane emissions – and converts it into a low-carbon replacement for fossil fuels,” said Dylan Chase, spokesman for the RNG Coalition (www.rngcoalition.com). “While producing other clean fuels usually requires extensive amounts of dedicated agricultural land or extensive amounts of clean power, for feedstock, RNG is captured from already existing methane emissions.”
One of the RNG Coalition’s primary objectives “is to better educate around the impact of methane emissions, which offer 80 times the climate-warming potential of CO2 on a 20-year timescale,” according to Chad Lindholm, senior vice president at Clean Energy (https://cleanenergyfuels.com), a coalition member. “This is a pernicious and overlooked part of global greenhouse gas emissions, which RNG uniquely addresses without major infrastructural additions or land-use changes.”
Derived from natural fats and oils, renewable diesel is chemically and molecularly equivalent to petroleum-based diesel. This makes it “a simple drop-in alternative fuel option for any diesel-powered chassis,” said Joe Korn, alternative fuels and emission reduction consultant for Holman (www.holman.com). He noted that renewable diesel “does not have stability issues commonly associated with bio blends of diesel.” Additionally, “tailpipe emissions are about the same as regular diesel, but since it is ‘renewable,’ the carbon intensity score is lower.”
Infrastructure Requirements
Of the three alt fuels, hydrogen presents the greatest infrastructure challenge. That’s because “private hydrogen stations are not readily available at this time, and in all likelihood, if they were, these stations would be extremely costly and highly complex,” Korn explained.
Wentlent acknowledged current infrastructure barriers but called attention to continued industry expansion: “Hydrogen fueling networks are still being built out, so cost and availability depend on geography. That gap is closing as production and delivery networks scale, but it’s real today.”
Public RNG fueling infrastructure is more established. Per Lindholm, “There are already well over 1,000 sites around the country that are open primarily 24/7. These are a great option when the station is close by and doesn’t have out-of-route miles or time-of-service impacts.” He noted that public fueling sites offer fleets the opportunity to pilot RNG programs.
Utilities have the option to build private, on-site infrastructure, which doesn’t have to be a complex undertaking. “Generally speaking,” Lindholm said, “tapping into existing gas lines and existing power to serve a site is not a challenge.”
Korn added that the “cost and complexity of an RNG fueling station depends on whether a fleet requires a high-pressure fast-fill option or can manage with simply a time-fill solution where vehicles are refueled overnight when not in use. High-pressure fast-fill systems can cost nearly five times as much as time-fill stations.”
Renewable diesel typically offers the fewest infrastructure barriers. According to Korn, “R99/R100 blends can simply be added to existing on-site diesel fuel stations and dispensers. However, some fleets may find it beneficial to separate the fuels if there is still a requirement for some equipment to operate on regular diesel.”
Total Cost of Ownership
Korn also pointed out that “the cost per kilogram for hydrogen fuel can be as much as $35. For comparison, a Toyota Mirai FCEV holds 5 kilograms of H2, which would cost $175 to fill with a range of approximately 400 miles. This equals about $0.43 per mile. A similar-class gasoline vehicle would cost about $0.13 per mile.”
Wentlent said the higher cost is primarily because infrastructure is still scaling but added that “total cost of ownership is more than fuel price. Fuel cell vehicles have fewer moving parts than internal combustion, no multispeed transmission and don’t suffer the utilization penalty of hours-long battery charging. For heavy-duty, high-utilization fleets, those factors can offset the fuel cost premium.”
Per Korn, RNG’s typical diesel gallon equivalent ranges from $1.50 to $2.25 compared to over $4 for diesel. “The cost of RNG or compressed natural gas will vary based on the volume of fuel a fleet consumes, but generally speaking, it is about half the cost of diesel fuel,” he said.
Renewable diesel can cost up to a dollar more per gallon than conventional diesel, Korn noted, “due to the unique refining process along with its low production volume and reliance on feedstock pricing as well as on state and/or federal incentives.”
Final Answer?
“There’s no one-size-fits-all solution for choosing an alternative fuel,” Korn said, “but if you burn less conventional fuel and/or transition to an alt-fuel option, you’re likely to save money and lower emissions.”
Wentlent explained that ultimately, “fleets don’t need to pick one fuel. The smart approach is matching the power train to the application.”
About the Author: Shelley Mika is the owner of Mika Ink, an Omaha, Nebraska-based branding and marketing communications agency. She has been writing about the fleet industry since 2006.