The situation may seem incongruous: in the Alpine valleys, elected environmentalists have long opposed the construction of a train line. Dedicated to linking Auvergne-Rhône-Alpes to Italian Piedmont, the Lyon-Turin rail tunnel is arousing debate: its construction is fifteen years behind schedule and its cost has exploded by 85% according to the European Court of Auditors. Its promoter, Tunnel Euralpin Lyon Turin (TELT), still defends that the work will make it possible to transfer freight from roads to rail, thus decarbonizing the flow of cross-border goods. However, the site’s carbon footprint leaves something to be desired.
The TELT estimated in 2012 that the construction of the cross-border link would generate 10 million tonnes of CO equivalent2 (teqCO2). Based on the contracting authority’s traffic estimates, the European Court of Auditors concluded that the emissions from the Lyon-Turin would only be offset twenty-five years after its entry into service. Provided that the projections presented were not overstated, the institution qualifies: “This prediction further depends on traffic volumes: if they reach only half of the predicted level, it will take fifty years from the entry into service of the infrastructure before the CO2 emitted by its construction is compensated.”
An example and a doubt sometimes used by aviation defenders to increase the carbon bill of trains. With reason?
Consider emissions to produce energy
First, we must recall the orders of magnitude. According the latest report from the Intergovernmental Panel on Climate Change (IPCC)15% of global CO emissions2 are produced directly by the transport sector. Even more so if we include indirect emissions: energy production and infrastructure construction. Because the artificialization of soils and the destruction of wetlands prevent the capture of CO2 by these carbon sinks. Still according to the IPCC technical summary, 70% of emissions come from road transport, 12% from aviation, 11% from maritime transport, and 1% from rail transport.
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The first factor to be taken into account when estimating emissions: the use and origin of the energies of the various types of transport. “That is to say the combustion, as well as the emissions linked to the upstream energies, details Nicolas Meunier, mobility expert within the Carbon cabinet 4. For transport propelled by electricity, it is for example the manufacturing emissions of nuclear and renewable parks. Similarly in diesel, you have to take into account the extraction, refining and transportation of oil.”
It is on these criteria that is based the French Environment and Energy Management Agency’s carbon emissions calculator (Ademe), which calculates the carbon footprint of any trip, but does not take into account the construction of vehicles or that of infrastructure.
To calculate the carbon footprint of the different transports, “taking into account the construction emissions of airports and rail is useless when you think in the short term for your next trip”, slice Nicolas Meunier. Emissions from the construction of railway infrastructure have already been emitted and are ultimately amortized by shifting passengers to this low-carbon transport, where airport and road infrastructure will continue to serve vehicles whose technologies do not currently allow to reduce its impact.
Effects on the climate excluding CO2
For an equivalent trip, “the plane is 40 to 130 times more emitting than the train, [selon] whether or not we integrate the Intercités, some of which have heat engines, compares Valentin Desfontaines, sustainable mobility manager at Climate Action Network (RAC) by basing its calculation on the carbon base of Ademe. A TGV journey costs 1.73 grams of CO2 per kilometer per passenger (gCO2e/p.km), against 230 grams of CO2 for a domestic flight.
The impact of aviation is heightened by the contrails of its devices. “It is a question of taking into account all the effects excluding CO2, says Nicolas Meunier, the plane will burn kerosene at very high altitudes, where the water vapors that result from combustion can form clouds, this is called condensation features. These clouds have a warming effect on the climate.”
Differences between construction and energy/maintenance emission factors of different modes of transport. | Carbon cabinet
And even by incorporating the construction of vehicles and infrastructures in the calculation of carbon emissions, the results obtained by the firm Carbone 4 underline the sobriety of the train over other modes of transport. For an equivalent journey, a TGV would emit 10 gCO22e/p.km, a 30 gCO coach2e/p.km, an electric car 51 gCO2e/p.km, a 109 gCO thermal car2e/p.km, and a 264 gCO aircraft2e/p.km.
A “common” train line amortized in twelve years
At the Lyon-Turin site, a monumental project across the Alps, Valentin Desfontaines prefers to take as an example the construction of the LGV Rhine-Rhône line, which is more common. Open to traffic since 2011, this high-speed line connects the Grand-Est and Bourgogne-Franche-Comté.
Its carbon footprint, entrusted by Ademe, SNCF and RFF (Réseau ferré de France) to the firms Objectif Carbone, Altern Consult and Inexia, unveils the carbon bill for its first thirty years of operation. Design, construction and operation should generate 1.9 million teqCO22of which 42% due to works and 53% to the production of energy for traction.
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“On average, 1.2 million people should be diverted annually from road and air thanks to the new TGV Rhin-Rhône offer”figures the study for a period between 2012 and 2042. That is a saving of 3,895,000 teqCO2 over thirty years.
The line would become “carbon positive” by 2024, ie the emissions avoided will be greater than the emissions generated by its design, operation and maintenance. A result that is all the more advantageous since, as the study points out, “the operation and the environmental benefits of the line will continue well beyond the thirty years taken into account in the calculation, the lifespan of an infrastructure being around a hundred years”.