Diesel engine emissions advancements and overall capabilities cannot be ignored as the transportation industry tries to balance mitigating climate change and decreasing fossil fuel access with critical productivity and uptime, so concludes a new report on the necessity of internal combustion engines (ICE) heading into a zero-emissions future.
The Engine Technology Forum (ETF) study focused on the near-term needs of the transportation industry and the capabilities of current ZEV solutions. The ETF, known as the Diesel Technology Forum until October 2023, unveiled the report in May 2024. The study, entitled Powering On: Internal Combustion Engines & the Clean Energy Future, aims to emphasize the need to use multiple types of powertrains, particularly ICEs, in the coming decades alongside EVs, hydrogen, and biofuels.
“I think in this whole area, we have to be careful about what we understand or think we know about switching to alternative fuels or zero emission technology, because there's more than one way to get carbon reduction, and I think ultimately we should value all those ways,” said ETF Executive Director Allen Schaeffer.
The report begins by examining the current state of diesel fuel in the U.S. to emphasize the role of ICEs in the industry today – and how difficult this fuel would be to replace.
“We have a ways to go,” Schaeffer stated. For comparison, “Last year, there was about 3.5 billion or so gallons of biodiesel and renewable diesel consumed in the US, and about 44 billion gallons of petroleum diesel.”
Heavy-duty vehicles are especially dependent on diesel, with the ETFs report citing a 2021 M.J. Bradley & Associates study that over 95% of large Class 7 and 8 trucks have diesel engines. Despite both climate and economic motives for the industry to reduce their reliance on the fossil fuels diesel engines call for, the ETF also noted that their viability as an energy source is hard to replace due to their energy and power density, ease of storage, and established distribution infrastructure. Due to this utility, “fossil fuels’ share of global primary energy consumption was at about 82%, a percentage that has declined only marginally over the last decade (from about 86% in 2012),” the report said, referencing data from the Energy Institute Statistical Review of World Energy 2023.
And not only are ICEs and fossil fuels hard to replace, but renewable fuels come with their own difficulties, including infrastructure implementation and lack of financial and physical resources, a lack of cultural readiness to change to habits that would support alternative energy sources, and inequal social repercussions. For these reasons, plus the limitations of trucks with alternative powertrains, the ETF’s report argues that current emissions regulation deadlines are not realistic.
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“I think a lot of people lose track of the idea that the whole trucking industry was built around the performance of diesel,” Schaeffer explained. “When we talk about changing fuels in the trucking industry, we're not just talking about buying a new truck and fueling it slightly differently. You're talking about, ‘Can it haul the same amount of weight?’ If not, then I need more trucks to serve my customers.”
Additionally, the ETF argued that some alternative powertrains may have higher emissions than diesel engines with renewable fuel, such as battery-electric vehicles. Even alternative powertrains beyond electric vehicles come with their own pitfalls, the white paper noted, like hydrogen.
“For example, once you've made hydrogen, transportation is an issue,” Schaefer said. “Ideally, particularly to control costs, you would try and use it close to where it's being produced. I think that's really the limiting factor at this point.”
Currently, there are 54 light-duty retail hydrogen stations according to the California Air Resources Board (CARB), and only one mixed-light, medium- and heavy-duty retail hydrogen station. And costs at these stations have increased, as CARB’s Annual Evaluation of Fuel Cell Electric Vehicle Deployment & Hydrogen Fuel Station Network Development found that the price for a kilogram of hydrogen rose from $14.95 in Q2 2022 to over $20 in Q1 2023.
Emphasizing diesel’s role in cutting carbon emissions
Due to the factors impacting alternative powertrains, the ETF argued that ICE advancements powered by low-carbon fuels, such as biofuels and e-fuels, will have a significant impact in a zero-emissions future. This included outlining recent efficiency and emissions improvements, such as developing integrated ICE-powertrain-vehicle systems, using hybrid technology, and increasing Brake Thermal Efficiency. The growth of freight efficiency improvements via improved aerodynamics, decreased rolling resistance, engine refinements, and decreasing drivetrain losses are also ways ICEs can help reduce emissions.
The report also delved into renewable diesel’s ability to reduce lifecycle greenhouse gas emissions, with another ETF report stating that this fuel source can cut GHG emissions by 50-85% throughout its lifecycle.
“[The renewable biofuel] industry anticipates being able to hit 5 billion gallons annually by 2025,” Schaeffer stated. “There's tremendous growth in this area, and not just from investments from midwestern producers, but also from the petroleum industry itself. Traditional refiners like Chevron, Phillips 66, and Marathon are bringing on capacity to produce more renewable biofuels, like renewable diesel.”
According to another ETF study 2022, turning over older diesel vehicles to ones newer than 2010 would reduce more greenhouse gas emissions at 25% of the cost.
“There is no single best solution to reduce carbon emissions in all sectors, which is why we must embrace all steps toward reducing carbon; internal combustion engines are clearly part of the solution,” Schaeffer concluded.
