USA – After attending the Advanced Clean Transportation Expo in the past two years, we were of the view that the USA may catch up with Europe to become the world’s largest electric vehicle market after China. Following the 2025 edition of the ACT Expo – held between 28 April and 1 May in Anaheim, California – I now have serious doubts about how long it will take for America to overtake Europe, if it happens at all. There was a palpable shift away from electric vehicles in favour of alternatives such as natural gas, propane, and hybrid vehicles. Once the stars of the show, these options faded into the background when California’s zero emission vehicle mandate passed into law. Now, the progressive state has repealed the mandate, after the Environmental Protection Agency in January 2025 withdrew the waiver which allowed California to enforce zero emission quotas on fleets; consequently, the low-emission alternatives to diesel and electric are enjoying a revival of interest from many kinds of customer.

That is not to say that there were no electric vehicles at all: indeed, International, Kenworth and Peterbilt launched new Class 8 trucks with all-electric drivelines, and major Tier-1 suppliers showcased their e-powertrain components and battery packs. Erik Neandross – the CEO of a consultancy (GNA) which is a subsidiary of the organisation (TRC) that hosts ACT Expo – told delegates that there is “no going back” on the road to zero emission transportation, as American industry continues to invest in advanced clean technologies. Indeed it does, but how clean is “clean”? Having narrowed to mean only vehicles which produce zero emissions at the tailpipe, the definition of “clean” is once again expanding to include vehicles that can significantly reduce, without entirely eliminating, the transport sector’s greenhouse gas emissions.

At the last two shows, I observed that America was more open to alternatives such as natural gas, though electric was the clear favourite. Now, electric has lost that special favour. Instead, what I saw at this year’s show was an atmosphere of healthy confusion, a sense of possibility and a feeling of optimism that has not yet devolved into a mind-numbing bewilderment.

Not everyone believes that the new government is responsible for this state of affairs. Scott Brinner, from natural gas infrastructure firm Nopetro Energy, told Truck & Bus Builder that Cummins’ ‘X15N’ natural gas engine is a “gamechanger” for the industry and could slow down the electrification of the heavy-duty segment. Others echoed the view that natural gas and other fuel options were bound to come back, regardless of what the federal government does, thanks to improvements in technology and the expansion of renewable sources from waste. Jennifer Rumsey, chairwoman and CEO of Cummins, delivered the keynote on the first day of the show, reiterating the company’s commitment to fuel and energy agnosticism. However, the focus of the company’s showcase was not natural gas but a concept hybrid drivetrain, assembling parts from Cummins, ‘Accelera’, and transmission partner Eaton. It demonstrated how powertrain components which are quite different from one another – engines, motors, transmissions, battery packs – can be flexibly combined and applied to several use cases. For Cummins, it is not “either or” but “both”: both electric and internal combustion, used separately or together.

Appropriately, in her speech, Rumsey called for unity among manufacturers and suppliers, claiming that hybrid and alternative fuels represent “increasingly balanced and pragmatic solutions”, while battery electric remains “essential” for certain applications. She said that the industry needs “clear and challenging, yet achievable targets” for decarbonisation, making the overall approach “fair and unbiased” towards every technology. In other words, governments should not try to regulate driveline options out of existence. On the same note, she argued that lifecycle emissions should be taken into account, meaning that vehicle emissions should not be judged solely at the tailpipe. The market for alternatives to diesel has been blown wide open: despite the confusion, the general hope is that each segment and each application will discover the right option at a price point that is not dependent on generous incentives. 

Cummins' hybrid powertrain concept

Natural gas: Nopetro Energy

During the show, I spoke with Scott Brinner, who is executive vice president of Nopetro Energy’s renewable natural gas business. Founded in 2007, the Miami-based company began by consulting on natural gas fuelling projects for local authorities. Its first contracts were public-private partnerships to set up and maintain fuel stations for fleets such as ‘Lynx’ – the public transit system serving Orlando, Florida – and the Leon County school district. For Lynx, Nopetro aided in the procurement of more than 150 CNG buses and the build-out of fuel stations and maintenance facilities to support them. For Leon County schools, Nopetro helped in switching half of the school bus fleet – 105 buses – to natural gas. According to Nopetro, Leon County school district has saved more than USD1.1m in fuel costs and reduced its vehicle emissions by 90% since 2012.

Three to four years ago, Nopetro made an important change to its business model. Previously, it was responsible only for setting up fuel stations for its clients, sourcing natural gas from third-party suppliers. Later this year, the company will open its first production facility, converting methane to renewable natural gas at a landfill site in Vero Beach, Florida. Twelve months later, the company plans to open a second facility, and six to twelve months after that, it will open a third, supplying renewable natural gas to the fifteen fuel stations it operates on behalf of its clients. Nopetro’s renewables business is supported by New York investment firm, Nova Infrastructure Partners.

With the opening of its first RNG production facility, Brinner said that Nopetro will become one of a small number of vertically-integrated suppliers of renewable natural gas and infrastructure solutions. Its business model mirrors that of several “turnkey” electrification companies that have appeared over the past several years, except that it offers a fuel option which has a net-negative emissions impact, burning gas that would otherwise be emitted into the atmosphere as a waste byproduct. Brinner called Cummins’ latest natural gas engine a “gamechanger” for the industry, overcoming the limitations of the 12-litre version that had prevented the use of natural gas in the most demanding applications. With its long-term supply contracts, Nopetro takes away much of the upfront cost and hassle of transitioning to natural gas from public and municipal fleets who cannot or choose not to switch to electric. 

Propane-fuelled chassis at Blue Bird stand

Gas and hydrogen storage: Quantum Fuel Systems

Gaseous fuels, whether they be natural gas or hydrogen, have to be stored in a different way to petrol and diesel. A specialist in onboard fuel storage systems since the late 1990s, Quantum Fuel Systems presented systems for natural gas and hydrogen at the ACT Expo based on its latest technology. Designed for storing fuel at the back of a Class 8 cab, these systems can be combined with a module for mounting tanks on the frame rail of the truck. The natural gas system stores the fuel at 250 bar pressure, whereas the hydrogen system stores it at 700 bar. With a new tank design, the natural gas system can store fifteen gallons more than the company’s previous model. It will enter customer trials later this year in preparation for production in 2026. The hydrogen system was originally developed for Nikola’s prototype trucks and is now featured on Autocar trucks and on a demonstration vehicle developed between Accelera and Symbio.

I spoke with Mark Arold, president of mobility at Quantum Fuel Systems, who explained that the company went private in 2016 following a Chapter 11 restructure, when an existing investor bought 100% of the company stock. Today, the company has two areas of expertise: the design, development, and production of high-pressure tanks between 250 and 930 bar; and the integration of fuel storage systems on trucks and on “virtual pipeline” trailers. The company has worked with hydrogen for over twenty-five years and claims to have been the first to certify a hydrogen tank at 1,000 psi, but so far it has not received enough demand to warrant high volume production of its hydrogen systems. Nevertheless, Arold believes that users of natural gas may eventually switch to hydrogen, using it as a combustion fuel first before transitioning to fuel cell electric.

Arold agreed that the Cummins X15N is a crucial development for natural gas as a fuel. He told T&BB that the X15N is the long-awaited “missing piece” that is opening up heavy-duty applications to natural gas. Thanks to this and the increasing availability of renewable sources, the natural gas sector is benefiting from “new tailwinds” that are unrelated to the recent change in government. In Arold’s view, electric does not work for many Class 8 applications, while hydrogen is still too expensive. Natural gas is therefore the perfect solution “right now”.

Propane-fuelled Nexio truck at Propane Education & Research Council stand

Propane as a fuel: the Propane Education & Research Council

One fuel option which receives very little attention is propane, a byproduct of processing natural gas and petroleum with the molecular formula “C₃H₈”. Since 1996, the Propane Education & Research Council has aimed to change this through its promotion of research and development projects using propane as a fuel. At its stand at the ACT Expo, the council showcased two vehicles: a heavy truck developed by Nexio and equipped with a 7.2-litre V8 fuelled by autogas (a mixture of propane and butane); and a Chevrolet pickup truck fitted with a direct injection propane engine developed by Stanadyne. On its own stand, Blue Bird, known otherwise as a supplier of diesel and electric school buses, elected to present a medium-duty chassis with a propane driveline.

Joel Stutheit, senior manager autogas business development, explained to T&BB that propane has been used in fuel mixtures for over seventy years. In the 1970s and 1980s, propane engines fell into disrepute due to power losses, but the technology is now catching up, making it a solid alternative in Class 3-7 applications such as regional deliveries and school transportation. One of the unique benefits of using propane is the massive reduction in nitrous oxides and particulates produced by the engine: NOx emissions can be reduced by as much as 96% compared to diesel, while particulate matter can be almost eliminated, all without using aftertreatment.

Stutheit told T&BB that, in the USA, thirty billion gallons of propane are produced every single year, of which roughly a third is consumed domestically, while the rest is exported. As diesel, more renewable forms of propane can be produced synthetically. In Stutheit’s view, propane could be a serious contender as an alternative to diesel, with domestic availability and a cost parity lower than diesel in applications such as school transport (30 cents less expensive per mile). The council is now calling for regulators to put propane on an equal footing with other low and zero carbon options when, for example, developing incentives for fleets to transition from diesel.