While the trucking industry seems hyper focused on the push toward electric vehicle technology, there are green alternative fuels — such as renewable versions of diesel, propane autogas and natural gas — that are ready and available for adoption today.
The electrification effort is making strides in the industry, especially in California, where the state has embarked on a strategy to transition its freight sector away from fossil fuels to electrification and reduce nitrogen oxides and particulate matter. But the pace and cost of building out the infrastructure in North America is still uncertain.
Roush CleanTech President Todd Mouw put it perfectly: the U.S. seems to have “shiny penny syndrome.”
“About 10 years ago, everything’s natural gas. Now everything’s electricity,” he says. “While developing electric trucks makes sense, there are a lot of barriers that still have to get knocked down for that to be mainstream.”
As the electric market takes the time to mature, what are the options for fleets to make their internal combustion engines greener now?
The Case for Renewable Diesel
“Green” goals aren’t just for fleets in the market for a new truck. Renewable diesel offers fleets the option to use traditional powertrain technologies and fueling infrastructure while reducing greenhouse gas emissions by 75% compared to fossil petroleum diesel, according to Neste, a producer and supplier of renewable diesel. The company has renewable diesel delivery points at more than 1,400 locations across California and Oregon.
Renewable diesel can be used in diesel-powered vehicles without any engine modification and can be distributed through existing infrastructure. These characteristics make it a perfect “drop-in fuel” to reduce emissions for existing heavy-duty diesel trucks that still have life in them to be in service for another generation.
“The effort that will be associated with the change from the petroleum diesel to the renewable diesel can be overnighted, because the infrastructure is already there,” explains Carrie Song, North American vice president for renewable road transport at Neste. “There’s really no need for investments into additional infrastructure. We can just leverage the current available assets.”
Unlike biodiesel, renewable diesel is approved for use in diesel engines by most heavy-duty engine manufacturers, according to clean-energy transportation consultants Gladstein, Neandross & Associates.
While it’s more expensive than traditional diesel, one of the “beauties” of renewable diesel, as Song puts it, is that traditional and renewable diesel are fully compatible and interchangeable. Renewable diesel meets the same ASTM D975 standard as petroleum diesel.
Neste says its fuel also earned a Top Tier Diesel Fuel certification. This designation means the fuel meets standards written by vehicle manufacturers to reduce fuel injector deposits, increase lubricity for less wear on critical fuel system components, improve fuel stability, and increase protection against water and particulates introduced into the fuel before being dispensed into the vehicle or equipment.
Renewable diesel currently is predominantly available on the West Coast and in Canada, due to strong legislative backing from state governments that support programs for transitioning to cleaner fuels. This push has also driven awareness of the alternative fuel, which has led to private fleets pioneering adoption of it, Song says.
In addition to existing suppliers such as Neste and Renewable Energy Group, Love’s and Cargill recently announced a joint venture to produce and market renewable diesel.
Renewable diesel production also produces another renewable fuel as a co-product: renewable propane.
Using Renewable Propane in the Medium-Duty Trucking Segment
While propane hasn’t hit the market in heavy-duty applications because there’s not a large enough displacement engine available, many owners of medium-duty vehicles (Class 4 through Class 7) have adopted propane autogas to reduce emissions. Roush CleanTech deploys upwards of 4,500 propane units a year in these vehicle classes (a number which includes their largest customer: school bus fleets).
Renewable propane is chemically the same as conventional propane, so the fuel is interchangeable. If a truck operator puts renewable propane in a conventional propane engine, it would operate the same, just with a cleaner emissions profile.
In comparison to electric charging and renewable natural gas infrastructure, propane fueling infrastructure is simpler because it’s a low-pressure fuel, Mouw explains. However, currently there’s not a lot of commercially available renewable propane — only about 5 million to 10 million gallons, Mouw estimates.
The fueling industry is also working on a blend of propane with dimethyl ether. DME can be produced from a variety of feedstocks, including dairy biogas, food waste, and waste streams from industrial processes. This creates a fuel with the characteristics of conventional propane but with a lower carbon intensity that would qualify it for incentives under California’s Low Carbon Fuel Standard, according to the National Propane Gas Association.
“The propane industry recognizes that we can’t just get [to a zero or negative carbon intensity] with conventional propane,” Mouw says. “We’re going to have to use the supply of conventional propane and mix it in with renewable propane or DME or renewable DME to showcase to the regulatory agencies that we are getting cleaner from emissions profile perspective. “
Could renewable propane become another cleaner alternative in heavy-duty applications?
If a large enough engine were developed, Mouw says, renewable propane would play very well in the heavy-duty market. It’s a high-octane fuel, and because it’s a liquid, a lot of fuel could be packed on board. Furthermore, many truck stops, such as Love’s, already have propane infrastructure on site for recreational vehicles
However, while natural gas infrastructure is more expensive, long-haul trucks traveling longer miles would end up spending more on the cost of propane in the long run, Mouw speculates.
Renewable Natural Gas as a Drop-In Replacement
Renewable natural gas is another drop-in replacement that provides an ultra-low emission, carbon-negative solution, this time for a compressed natural gas engine. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards, according to the Department of Energy.
Nearly 90% of surveyed fleets that have CNG vehicles intend to use RNG in the next year, the highest rate of any renewable fuel or energy source across all drivetrains, according to the State of Sustainable Fleets report published by Gladstein, Neandross & Associates.
RNG use in on-road transportation grew in California (where RNG dominates) from 69% in 2018 to about 93% of total volume in 2020 — a more than 225% increase from 2015. In the fourth quarter of 2020, RNG grew to 98% of all natural gas used as a transportation fuel in the state.
The National Ready Mixed Concrete Company recently deployed 24 compressed natural gas concrete mixers from Peterbilt, expanding its Southern California fleet to 117 CNG trucks — fueled with 100% carbon-negative RNG produced in California.
To help fulfill a company-wide commitment to reducing the carbon footprint of its operations, the concrete supplier began converting its heavy-duty fleet of mixers and haulers to near-zero natural gas trucks in June 2020. About half of the fleets’ trucks run on RNG, while the other half have been running on renewable diesel for several years.
NRMCC’s fleet of concrete mixers, cement and material haulers travel throughout Southern and Central California, relying on Cummins Westport natural gas engines.
“In the past year alone, NRMCC has driven nearly 5 million miles with our CNG fleet fueled by RNG,” NRMCC President Steve Lode said in a press release. “There is no other low- or zero-emission technology available today that could enable a heavy-duty fleet like ours — running routes from Southern to Central California pulling heavy loads of cement — to offset the level of greenhouse gas emissions reductions that we’ve achieved.”
NRMCC’s fleet will consume more than 1.2 million diesel gallon equivalent of RNG, fueled in part at its private natural gas station built at its Vernon plant. The RNG has a carbon intensity score of negative 200, enabling the company to reduce its carbon dioxide emissions by more than 42,000 metric tons each year.
Three additional private RNG stations are scheduled to be installed by the end of 2021 at its Irwindale, Glendale, and Santa Clarita locations.
“The decision to invest capital in our own infrastructure does the following: helps to ensure our equipment is fully fueled to 3,600 psi; fuel without any potential of waiting in lines at public stations; and provides a better ability to budget and manage a stabilized purchase cost of RNG fuel,” Lode told HDT in an email.
NRMCC’s investment in RNG was supported by a $15.7 million grant.
While the industry’s electric future takes the time to mature, fleets have several options for making their internal combustion engines and operations greener through renewable fuels.
[Editor's Note: This article, which first appeared in the September 2021 print issue of Heavy Duty Trucking, includes a correction. According to Neste, renewable diesel delivers a 75% lifecycle GHG reduction, not 80%, as was originally reported.]