By Daniel O’Brien, Content Manager & Communications Advisor, Autonomy

The Business of Mobility is a series of articles featuring business leaders in sustainable mobility. 

Recently Engineered News-Record (a magazine) ranked SYSTRA as among the world’s top three engineering firms specializing in ‘Mass Transit & Rail’. Founded following the merger of subsidiaries of SNCF (France’s state-owned rail entity) and of RATP (Paris transport operator and infrastructure manager), it is developing mobility solutions worldwide. Mobility Systems Business Unit Director, Laurent Mezzini, discusses how SYSTRA is approaching the challenge of decarbonizing rail. 

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Laurent Mezzini, Business Unit Director, Mobility Systems at SYSTRA

Daniel O’Brien: Laurent, tell us about your background.

Laurent Mezzini: My career began in the oil and gas industry, and I’ve worked across various industries. When I started working in public transport and mobility, it struck me how passionate many people are about the ecological transition. I’m very privileged to be part of a business that is not only dynamic and innovative, but that is leading the way in decarbonizing transport.   

Daniel: Given that rail is both public and electric, one would consider it ideal for our new low-emissions age. 

Laurent: Rail is a great part of the solution when it comes to decarbonizing rail. The train is already the lowest-emitting transport mode per passenger compared to airplanes, cars and buses. Rail transport is only responsible for 1% of global CO2 emissions, whereas road transport for passengers accounts for 45% of global CO2 emissions. Unfortunately, not all buses or trains are electric. In France, for example, we have around a thousand trains still running on diesel. The metro is all-electric, but around 40% of our longer distance services do not have catenary (overhead lines), and therefore diesel is required. 

Daniel: Europe has committed to ending the sale of fossil fuel vehicles by 2035. Will rail be ahead of the vehicle industry in terms of emissions? 

Laurent: The conversion of the automotive fleet to electric is on the way, but let’s be clear, considering the origin of electricity still relies heavily on fossil fuels, an electric vehicle does not necessarily have a better global energy efficiency nor CO2 impact than a modern diesel car. The energy transition in the power system needs to happen in parallel with this transformation. Retrofitting cars, buses or trucks to electric is possible, but the return on investment is not favorable.

When it comes to rolling stock, it’s feasible and economically viable to retrofit existing stock for reduced emissions. Considering its long (about 40 years) lifecycle, diesel exit needs to be anticipated and motorisation change can be managed within the scheduled mid-life renovation programs. Most stakeholders in the industry are considering it.

Daniel:  Retrofit with what sort of engine?

Laurent: Biodiesel or biogas is the simplest retrofit as it requires a small adaptation on the motorisation only. It is more complex to retrofit diesel engines to be electric powered by batteries or hydrogen fuel cells. It requires careful feasibility and safety studies.   

Daniel: How can a battery possibly produce the necessary power to move a train of twenty coaches up a hill?

Laurent: Yes, that’s a challenge, and it is why hybrid models are being considered. You use the batteries when there are no overhead lines and then charge them up when there are or when you reach a station or the depot. When we consider a retrofit, we assess the energy needed for the service, the feasibility of retrofitting the motorisation, the availability of various types of energy at the charging points and the operational impacts (charging time).

Daniel: You feel trains should be given a bit more leeway in terms of the aspiration for net-zero?

Laurent: I think we have to take a step back. Many trains here in France are already net-zero and have been for decades. Think of our metros or very high-speed lines, which are all electrified, and our power system is heavily dependent on nuclear power. All those journeys being taken, for example, on the Paris Metro network, are largely emission-free. That’s an extraordinary achievement and one that was in place decades ago. Trains offer the utility of bulk transport as well as the efficiencies gained by rail traction engineering, whereby it takes minimal energy to move massive loads.  

Daniel: What about the debate between batteries and fuel cells?

Laurent: The advantage with hydrogen fuel cells is that you do not need to recharge the battery. Your feedstock comes from an on-board tank of pressurized hydrogen, which is faster to recharge. It would be ideal if this hydrogen could be harvested from the atmosphere. Today, most hydrogen is still made from methane in a process that releases emissions. But we’re starting to see progress away from this form of gray hydrogen toward green hydrogen, whereby it’s produced using renewable energy by a system of electrolysis. By making hydrogen with renewable energy, we are effectively storing electricity without the need for large batteries. Denmark’s wind energy hubs project for instance includes this green hydrogen component. 

Daniel: It seems then that there is no silver bullet for decarbonizing rail.

Laurent: Engineering is about small, incremental improvements that add up over the long run. In terms of transport and logistics, rail boasts the lowest emissions. Our decisions also depend on the broader energy system. If, in a few years, green hydrogen is being produced cheaply and abundantly, then that could become the ideal retrofit for our diesel locomotives. 

We need to take a nuanced approach to retrofitting current stock since hydrogen and biogas are dependent on the development of large-scale production and distribution circuits. In the meantime, it’s an exciting time for a systems engineer like me to factor in carbon when considering innovations and modifications for rail.

This interview has been edited and condensed for clarity.