Gas-retrofitted trains for greener railways?

The Nouvelle-Aquitaine Region launches the prototyping phase of its first retrofitted TERs running on renewable BioGNV.

Following the November 13 webinar focused on the challenges of BioGNV, the Nouvelle-Aquitaine Region confirmed its intention to carry out a retrofit operation on X73500 TER units, in partnership with FERROCAMPUS and GRDF. The project involves replacing the MAN diesel engines and their tanks with a propulsion system running on BioGNV, a renewable gas derived from biomethane. The initiative, included in the NeoTerra roadmap, now enters the prototyping phase, with a call for tenders scheduled for early 2026.

Environmentally, studies presented during the webinar indicate that BioGNV is one of the most effective alternatives to diesel for non-electrified rail. Projections forecast up to an 85% reduction in carbon emissions (well-to-wheel), as well as a significant decrease in air pollutants—particularly nitrogen oxides and fine particulates—estimated between 75% and 95% for the fleet in question.

Retrofitting proves attractive

The economic analysis highlights the appeal of retrofitting as an intermediate solution between keeping existing rolling stock and full renewal. The investment cost is lower than purchasing new units, which could defer the replacement of the X73500 fleet by 10 to 15 years. Operating expense projections also show potential fuel savings: BioGNV, whose price is considered stable and competitive, could generate up to €60 million in savings over 20 years for 53 units.

The project also includes operational and user benefits, with expected reductions in noise, vibrations and smells at stations, improving the environment for passengers and local residents.

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Finally, the Region emphasizes that this approach relies on a growing biomethane sector, supported by a substantial agricultural and forestry base and nine new injection units commissioned in 2024. The prototype planned for 2026 will validate the technical choices before a possible wider rollout.

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