Hydrogen Rail Decarbonisation: A Latvian Retrofit Model
Hydrogen locomotives keep losing the efficiency argument to battery-electric trains — but that critique targets fuel-cell trains, not the battery-hybrid retrofit a Latvian SME and Riga Technical University are now validating on Europe's ageing diesel fleet. We look at the efficiency case, the retrofit economics, and what the SME–academia model behind it means for the wider Baltic hydrogen ecosystem.
INNOVATIONSNEWS
PtXBaltic
8/18/20265 min read
While still challenged by high costs and low availability, green hydrogen is an increasingly viable route to decarbonising heavy transport — but rail is the one mode where hydrogen's business case keeps getting publicly challenged, not quietly assumed. At RailTech Europe 2026 in March, leasing executives and Deutsche Bahn engineers said out loud what plenty of operators think privately: hydrogen locomotives don't pencil out next to battery-electric alternatives. A Latvian SME and Riga Technical University think the argument is incomplete, and they have an EU-backed project running right now to make the case.
The efficiency argument against hydrogen trains, and why it isn't the whole story
The critique isn't vague. At RailTech Europe 2026, Mark Remie, an executive at a locomotive leasing company, put it plainly: “We have not seen any positive business cases for hydrogen in locomotives.” Deutsche Bahn's Lennart Fink backed the point with numbers — hydrogen's well-to-wheel efficiency sits around 25%, against 90%-plus for battery or catenary-electric systems. That's not a rounding error, it's a structural gap. Add refuelling infrastructure that costs roughly three times as much to build as diesel equivalents, and hydrogen fuel running about three times pricier than diesel at today's prices, and it's easy to see why an operator like Nexrail is ordering 200 battery locomotives for the Rotterdam–Genoa corridor instead of hydrogen units.
None of that is wrong, and we're not going to pretend otherwise — it's exactly the kind of caveat that should sit alongside any hydrogen-rail story. But the critique is aimed almost entirely at fuel-cell trains running on pure hydrogen, on routes where full electrification is a realistic alternative. That's a narrower target than “hydrogen in rail” as a whole, and it isn't the problem HYBUHTRAIN is trying to solve.
What changes when you add a battery to the hydrogen engine
HYBUHTRAIN — HYdrogen engine Battery plUg-in Hybrid TRAIN — doesn't use a fuel cell. It retrofits a hydrogen internal combustion engine (H2-ICE) alongside a modular battery pack and an energy management system, recovering energy under braking and topping up overnight. The project, approved through EIT Urban Mobility's Strategic Innovation Open Call, expects that hybridisation to cut hydrogen consumption by 20–35% compared with running the H2-ICE alone — which is precisely an attack on the efficiency gap RailTech's critics pointed at. It won't close a 65-point efficiency gap outright, nobody involved is claiming that, but it moves the number in the direction the sceptics say it needs to move, on a segment of the fleet where a fuel cell or full electrification isn't the realistic alternative anyway.
The same hybridisation also delivers stronger short-term power than the diesel engine it replaces, a longer range between refuelling stops, and zero-emission running through stations and city centres — the two things, fuel efficiency and local air quality, that matter most to an operator deciding whether to spend money on this instead of something else.
Retrofit is a different market than the one the sceptics are describing
Here's the distinction that tends to get lost: the RailTech 2026 argument compares hydrogen fuel-cell trains against battery-electric trains, largely on corridors where overhead electrification or plug-in charging is achievable. HYBUHTRAIN and its predecessor HYIPTRAIN are aimed at something else entirely — the diesel units that are neither getting replaced nor running anywhere near a catenary line any time soon. DIGAS estimates thousands of diesel trains built between 2000 and 2021 fit that description across six EU countries. For that fleet, the choice isn't hydrogen versus battery-electric; it's retrofit versus nothing, because a new zero-emission train costs roughly 13 times more than the ≈€0.9 million retrofit price tag, and most of those operators don't have that capital sitting around.
That's also why the 18-month timeline matters more than it might first appear. Taking the technology from TRL 6 to TRL 9 — validated prototype to full certification — including a three-month passenger trial, is an aggressive schedule for rail. It's only credible because DIGAS isn't starting from a blank page: HYIPTRAIN, a €892,348, 18-month project run with Ukrainian partner Mikroluch, already developed and certified the underlying H2-ICE retrofit kit on a passenger train operated by SKPL in Poland. HYBUHTRAIN is the second lap, not the first.
A Latvian SME and a technical university, actually working together
This is where the story gets interesting for the wider Baltic hydrogen ecosystem, beyond the trains themselves. DIGAS is a Latvian SME — the kind of company that, a few years ago, might not have had the credibility to lead a five-partner European consortium spanning Latvia, Ukraine and Poland. It's doing exactly that now, and building a track record to match: alongside HYBUHTRAIN, DIGAS has separately signed with Iarnród Éireann, Ireland's national rail operator, to retrofit a diesel freight locomotive using the same hydrogen-combustion approach, a project that also draws on EIT Urban Mobility funding. Two countries, two fleets, the same Latvian engineering team behind both.
Riga Technical University's role in HYBUHTRAIN is independent scientific validation — measuring real-world CO₂, NOₓ and particulate emissions once the train is running, and assessing scalability, economics and public-health impact. That's not a rubber stamp; it's the kind of third-party verification that gives regulators and future customers a reason to trust the retrofit kit beyond DIGAS's own numbers. RTU also coordinates EIT Community Hub Latvia — the country's formal link into the EIT innovation network — a fairly concrete signal that Latvian academia is positioning itself as infrastructure for the whole innovation ecosystem, not just a research partner on one project. An SME with export ambitions and a university with EU-network reach, doing applied validation work together on a live commercial project: that's a template worth Baltic hydrogen ecosystem stakeholders paying attention to, independent of whether trains are your focus.
The numbers on the table, and what's still worth confirming
The headline figures below are DIGAS's and the consortium's own projections, not independently audited results, and they're worth reading that way until the passenger-trial data is public:
Retrofit cost: ≈€0.9 million per train, versus roughly 13x that for a new zero-emission train
Hydrogen savings from battery hybridisation: 20–35%
CO₂ avoided: ≈200–230 tonnes per retrofitted train, per year
NOₓ and particulate emissions: cut by more than 95%
Technology Readiness Level: 6 → 9 over 18 months, including a three-month passenger trial
The five-partner consortium is DIGAS (Latvia, technology and commercialisation), Mikroluch (Ukraine, hybrid control systems), SKPL (Poland, train and operating environment), the municipality of Rzeszów (Poland, public engagement) and Riga Technical University (Latvia, independent validation) — a genuinely cross-border structure for a project this size.
What this signals for Baltic hydrogen ecosystem stakeholders
Two things worth carrying forward. First, the RailTech 2026 scepticism about hydrogen rail economics is largely correct about the market it's describing — but that market is fuel-cell trains on electrifiable corridors, not H2-ICE battery-hybrid retrofits on legacy diesel fleets. Conflating the two undersells a genuinely different value proposition, and HYBUHTRAIN's own hydrogen-savings target is a direct, testable response to the efficiency critique rather than an argument against its existing.
Second, and maybe more durable than any single train project: a Latvian SME leading a five-country consortium, backed by Riga Technical University's independent science and EU funding, is a pattern the wider Baltic hydrogen and Power-to-X ecosystem can study and repeat — in rail, and well beyond it. The molecules produced by Baltic electrolysers need somewhere real to go. A validated, cost-competitive retrofit market for the region's ageing diesel fleets is exactly the kind of near-term demand case that conversation has been missing.
Source: RTU helps validate a hydrogen-battery hybrid retrofit for Europe’s diesel trains