TRIALS of the United States’ first passenger hydrogen train are expected to begin this month. A Flirt H2 multiple-unit built by Stadler will be tested on the Arrow Line between San Bernardino Transit Center and Redlands University in southern California. All being well, full passenger service will begin in the autumn, with the hydrogen train working alongside two Flirt DMUs, which have been operating on the line since 2022.

This is just the start for hydrogen-powered rail transport in the Golden State. California has one of the most ambitious hydrogen rolling stock strategies anywhere in the world at the moment, with the California State Department of Transportation (Caltrans) expanding an initial order for four Flirt H2s to 10 in February. These will be used on the new Valley Line inter-city service in northern California from 2029, as our in-depth report in this month's edition of IRJ reveals.

Hydrogen-powered rolling stock remains a contentious issue in the rail sector. Many in the industry are sceptical of the merits of hydrogen-powered trains when compared with other forms of alternative traction. And they have a point. The optimal solution is always to electrify. Yet this is not always possible. Electrification projects are expensive and in the case of the United States, the Class 1 freight railways, which own the vast majority of the infrastructure on which passenger services run outside of the Northeast Corridor, are not currently considering electrification, with the costs far outweighing the benefits.

Batteries are often held up as the next-best alternative. However, Mr Kyle Gradinger, division chief of rail and mass transportation at the California Department of Transportation (Caltrans), makes a compelling case for why hydrogen was selected for the Valley Line service. He says that the greater range offered by hydrogen is better suited to the demands of Valley Rail, pointing out that around two-times the number of battery-powered trains would be required due to their limited range. The cost of installing charging infrastructure versus mobile and eventually fixed hydrogen refuelling stations is also prohibitive.

California has some of the strictest transport decarbonisation targets in the world and it is these state government regulations that are driving the crusade for alternative traction. A ruling from the California Air Resources Board (Carb) bans operation of any locomotive that is 23 years or older in the state from 2030. It also requires the introduction of clean traction in yards and for passenger locomotives in 2030, and for mainline freight operation in 2035.

While state agencies like Caltrans have no choice but to comply and work to reduce their reliance on and ultimately phase out diesel as quickly as they can, the freight railways are more reluctant and are challenging these rulings in court. They argue that compliance with the regulation’s timeline is impossible given the current results of research and development of zero-emissions locomotive technology. BNSF says it does not yet have a zero emissions locomotive that works.

A compromise is the likely outcome here. However, California is unlikely to remain an outlier. Similar regulations will become the norm elsewhere as measures to mitigate climate change begin to bite, requiring railways and fleet owners to actively introduce alternatives to diesel.

BNSF is correct to highlight that mainline alternative traction technology is not yet mature in the United States. But there is room for optimism in the progress that has been made elsewhere.

The steady replacement of diesel traction is a trend that we have been reporting on for many years; this issue of IRJ, for example, includes reports on Australian freight operator Aurizon trialling a battery tender for freight locomotives, and a project in Namibia to develop Africa’s first hydrogen-powered rolling stock. This year we have also reported on the introduction of battery passenger fleets in Germany and Italy. In Asia, Hyundai Rotem continues to progress the development of its hydrogen LRV, while CRRC unveiled its first hydrogen multiple-unit in February.

Work is also underway on converting diesel engines to hydrogen fuel. Latvian group Digas is working with Irish Rail on retrofitting a class 071 locomotive. The company is now seeking partners for a passenger train conversion project for which it has obtained European funding. The goal is to prove the viability of its technology, ideally in an Alstom Lint DMU.

Hydrogen is only viable as an alternative fuel source for rail if it is green and affordable. It is possible in California because Caltrans is riding the wave of the Biden administration’s Hydrogen Earth Shot Challenge, which is aiming to reduce the cost of green hydrogen from around $US 5 per kg to less than $US 1 per kg within a decade. The new Arches H2 Hub is a public-private partnership (PPP) hydrogen research and development initiative, which has $US 1.2bn to develop hydrogen technology for industries including transport. California’s commitment to introduce more renewable energy should also provide the capability to produce green hydrogen at the scale required.

Current hydrogen applications are niche, with infrastructure limited. However, a recent report from PricewaterhouseCoopers (PwC) predicts that demand will grow rapidly after 2035. Australia, the Middle East, Africa, Russia, and the United States - all places where the sun shines a lot and where the potential for solar power to produce green hydrogen is great - are likely strong production markets. Conveniently many of these countries have unelectrified railway networks of some size where distances are significant. As it has in California, the case for hydrogen traction in such places might prove to be just as compelling as the need to transition away from diesel intensifies.