Contributing to the transition of the railway industry by developing low-carbon rolling stock

In order to accelerate the decarbonisation of the railway sector, Alstom is developing new solutions to replace diesel-powered trains with trains using more environmentally friendly traction modes.

Main project's drivers for reducing the greenhouse gas (GHG) emissions

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Energy and resource efficiency

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Energy Decarbonisation

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Energy efficiency improvements

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Improving efficiency in non-energy resources

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Emission removal

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Financing low-carbon issuers or disinvestment from carbon assets

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Reduction of other greenhouse gases emission

Project objectives

Replacing trains using diesel traction with trains using alternative traction modes, further improving the carbon footprint of rail mobility (hydrogen traction, battery/diesel hybrid traction).

Detailed project description

Rail is currently one of the most environmentally friendly modes of transport (according to ADEME’s Carbon Footprint, trains emit 32 times less than cars and 23 times times less than air travel).

However, there is room for improvement, as some trains in operation are still powered by diesel. They represent about 20% of the trains running in France, but they cause emissions nearly 10 times higher than those of “electric” trains. Electrification of lines also remains a costly solution, especially for low-density lines.

This project led by Alstom aims to:

  1. structure and federate a French and European sector of excellence around clean rail technologies to:
    • Consider the hybridisation of the thermal fleet as a realistic solution both technically and economically to reduce emissions and operating costs, thereby contributing to important steps toward achieving the goals of decarbonisation;
    • Ensure the emergence of an ecosystem of French/European players in the forefront of clean technologies (H2, battery) in order to avoid dependence to non-EU partners;
  • Accelerate R&D / innovation in the industrial sector;
  • Develop a light hydrogen and/or a light battery train for small non-electrified lines
  1. Support and accelerate the investment policy of the Mobility Organising Authorities (AOMs – Autorités Organisateurs de la Mobilité) / Operators, by launching a plan to “green” diesel train fleets:
  • Converting the 650 recent regional diesel or dual-mode trains (AGC, Régiolis) to a hydrogen traction mode;
  • Replacement of the 300 aging light diesel trains (ATER) in circulation on short lines in the regions.

Emission scope(s)

on which the project has a significant impact

Scope 1

Direct emissions generated by the company's activity.

Scope 2

Indirect emissions associated with the company's electricity and heat consumption.

Scope 3

Emissions induced (upstream or downstream) by the company's activities, products and/or services in its value chain.

Emission Removal

Carbon sinks creation, (BECCS, CCU/S, …)

Avoided Emissions

Emissions avoided by the activities, products and/or services in charge of the project, or by the financing of emission reduction projects.

Avoided emissions: 

  • Quantification : around 500000 ktCO2 eq/ an

Every day, 20% of the trains running in France today are diesel trains, thus about 3500 trains (source: SNCF). According to ADEME’s carbon base, the carbon emission factor of a diesel train (0.028 kgCO2e/ for an average load) is more than 10 times higher than the carbon emission factor of a train with electric traction (0.00124 kgCO2e/ for an average average load).

With the SNCF Group’s CO2 emissions from rail traction at 1.4 MtCO2 in 2019 (source: SNCF’s 2019 corporate social commitment report), the replacement of diesel-powered trains by hybrid or green hydrogen-powered trains in the rail fleet could save at least a third of CO2 emissions, i.e. around 500 million tons of CO2eq/year.

Key points

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Invested amount

Not disclosed at this stage

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Starting date of the project

2014 - first hydrogen train project
2018 - first project in France

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Project localisation

France and Europe

Project maturity level

Prototype laboratory test (TRL 7)

For dual-mode hydrogen trains, in 4 French regions

Real life testing (TRL 7-8)

Pre-commercial prototype (TRL 9)

For hybrid trains, in 4 French regions

Small-scale implementation

Medium to large scale implementation

For hydrogen trains, in Germany, the Netherlands and Austria

Economic profitability of the project (ROI)

Short term (0-3 years)

Middle term (4-10 years)

Long term (> 10 years)

Not disclosed at this stage

Illustrations of the project

Hybrid vs diesel only benefit: reduction of fuel consumption, reduction of noise emissions (entry into stations), energy recovery during braking, improved sound in passenger areas, reduced maintenance costs.

H2 vs. diesel benefits: no GHG or particulate emission, reduced interior and exterior train noise, reduced vibrations, reduced maintenance costs.

Other benefits include:

  1. Decongesting the road network through modal shift;
  2. Strengthening the attractiveness of certain areas thanks to the “short lines” network;
  3. Structuring the French industrial fabric of excellence around clean technologies;
  4. Creating an ecosystem (e.g., incubator, start-up) favorable to innovation in the field of decarbonisation;
  5. Creating skilled jobs in the development and production of clean rail solutions;
  6. Massifying the use of decarbonated hydrogen to reduce production costs and make it available for other uses (e.g. mobility).

The use of hydrogen in the railway industry allows to massify the production and to reduce the costs

to pool distribution points for other forms of mobility in order to facilitate their promotion and thus contribute to the emergence of a hydrogen ecosystem in the territories.

The launch of hydrogen technology in public transport requires strong support from public finance.

Partnerships involved the development of Hybrid trains:

– French Regions (Grand Est, Nouvelle Aquitaine, Occitanie, Centre-Val-de-Loire)


– Ecosystem (local battery suppliers, suppliers of technological bricks, etc.)

Partnerships involved in the development of Hydrogen trains

– French Regions (Bourgogne Franche Comté, Grand Est, Occitanie)

– French State


– Ecosystem (local H2 suppliers, suppliers of technological bricks…)

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