Because the bridge over the Strait cannot be “green” as Minister Salvini claims

The Minister of Infrastructure and Transport Matthew Salvini often repeats a number to promote the construction of the bridge over the Strait of Messina. According to the leader of the League, once completed, the infrastructure will be “the most important work greens” because it will allow you to delete “140 thousand tons of CO₂” from the air. Salvini cited this estimate, among other times, on April 4 as a guest of the Foreign Press Association in Rome, on March 22 as a guest at Five minutes on Rai 1 and on 8 March by participating in an event on logistics in Verona.

But where does the number quoted by Salvini come from? And how reliable is it? We checked: the infrastructure minister’s statement gives a plausible estimate, but omits some important details.

The source of the data

When he talks about the “140,000 tons of CO₂” eliminated thanks to the bridge over the Strait, Salvini never mentions the source of the data. On one occasion the minister only mentioned, in a vague manner, “evaluations of more than ten years ago, which will therefore certainly be improved”.

In all probability, the estimate mentioned by the leader of the League is the one made in 2020 – therefore three years ago, and not ten – by the engineer John Mollica and relaunched in recent years by various local press sources. Mollica is a member of the Rotary Club of Messina, of whose local section he was treasurer, and is one of the founders of the civic network for infrastructure in the South, an association that has been promoting the construction of the bridge over the Strait of Messina for some time. “Our network fights for the bridge to be a territorial work: not only does it serve to unite Messina with the other cities of the country, but to make the territory grow, for example through the participation of local companies in the construction of the infrastructure”, he said explained to Green&Blue Mollica, who confirmed that he had met Salvini himself in recent months and presented his calculations to him.

In 2020 the engineer, together with his colleague Antonino Muscawrote a document titled “Notes on the emissions of harmful substances from ships and tires in the Strait of Messina”. The text is not publicly available, but Green&Blue he was able to consult it. Let us clarify immediately that this is neither a scientific study, carried out by researchers and subjected to the control of other scientists (the so-called peer reviewed), nor of an evaluation made by an institution, such as the Ministry of Infrastructure and Transport itself. Put another way, the text is a amateur work. The authors themselves are aware of this, writing in the document that “these Notes do not claim to be scientific, but aim to provide a contribution of healthy common sense and a general assessment of a highly harmful phenomenon”, i.e. CO emissions₂ and other harmful substances between Sicily and Calabria.

In short: the two authors quantified the lower emissions of carbon dioxide alone as a result of the construction of the bridge over the Strait at “over 140,000 tonnes per year”. To be precise, according to Mollica and Musca, the bridge would eliminate about 149,700 tons of CO₂ from the atmosphere and other harmful substances, such as nitrogen oxides and atmospheric particulate matter. How?

How the data was calculated

The two authors have considered the various ferries that carry passengers, cars and trucks in one year from one side of the Strait of Messina to the other. To calculate CO emissions₂ of the ferries the two engineers based their estimates on two factors: the power of ferry engines and the sailing hours.

According to Mollica and Musca, the annual emissions of CO₂ attributable to ferrying in the Strait of Messina would be around 150,000 tons. Once the bridge is built, the authors estimate in the document, the emissions produced by cars that will cross the new infrastructure will be equal to about 10,000 tons of CO₂ in a year. The difference between these two numbers is about 140,000 tons of CO₂those that according to Salvini would be eliminated thanks to the bridge.

The numbers mentioned so far should be taken with a grain of salt given the complexity of the matter. “There are two approaches to quantifying ship emissions. One is the method bottom up, which is based on factors such as the power of the engines (main and auxiliary) installed and the speed of navigation. The other approach is that top downwhich is based on the fuel consumption of ships, then converting it into emissions,” explained a Green&Blue Gianandrea Mannariniresearcher of the Euro-Mediterranean Center on Climate Change Foundation (Cmcc), author of various scientific articles on shipping emissions. “The first method is often used but, to avoid arriving at inaccurate results, it is also necessary to have information on the performance and actual activity of the ferry. For the second method, it is publicly available, for ships that touch European ports and pass the 5,000 gross tonnage, an inventory with CO emissions₂ aggregated on an annual basis”, added Mannarini.

The inventory is called THETIS-MRV and is managed by the European Maritime Safety Agency (EMSA). Here you can find the annual emissions of some of the larger ferries, such as helium, Cartour Delta and Epsilon, which cover or in the past have covered the stretch of sea between Reggio Calabria and Messina. For these ships, the order of magnitude of the total annual emissions of CO₂estimated with a method top down and updated to 2021, is close to what was calculated by engineers Mollica and Musca, using the method bottom up.

Even taking the calculations cited by Salvini for good, this does not mean that the reasoning of the leader of the League is complete. The estimate of 140 thousand tons of CO₂ “eliminated” thanks to the bridge over the Strait is in fact partial for at least two reasons.

What Salvini’s data doesn’t say

The first reason concerns, so to speak, an omission: in the calculations cited by the Minister of Infrastructure and Transport there are no CO emissions never mentioned₂ which would be produced with the construction of the bridge over the Strait. Consider, for example, the emissions for the production ofsteel he was born in cement necessary to carry out the work, or caused by the heavy vehicle traffic for the construction site.

The executive project of the work is not yet there, but the government has announced that it wants to restart from the project presented years ago by the Eurolink consortium, a group of companies led by the Italian construction multinational Salini-Impregilo, now renamed Webuild. We are talking about a bridge more than 3 kilometers longwhere the trains will also pass, held by thousands of cables and from pylons up to 400 meters high.

A spanometric calculation can be made on the quantity of these emissions. On its official website Webuild writes that they will be needed for the construction of the bridge about 400 thousand tons of steel. According to the World Steel Association, one of the world’s leading associations of steel producers, nearly 2 tons of CO are emitted on average during the production of a single ton of steel₂ in the atmosphere. This would mean that with the production of the steel necessary for the bridge over the Strait, roughly 800 thousand tons of CO₂. According to Webuild they will also be needed 1.5 million tons of cement for the construction of the bridge over the Strait. According to estimates by the International Energy Agency (IEA), the production of one ton of cement emits on average half a ton of CO₂. In this case, they can be estimated in spades over 700 thousand tons of CO₂ for the production of the cement needed for the bridge. Adding up the CO emissions₂ for the production of steel and cement, therefore, approx 1.5 million tons of CO₂a figure equal to ten times the approximately 150,000 tonnes estimated for ferry traffic in a year.

Without entering into the debate between those in favor and against the bridge, it is therefore undeniable that the construction of an infrastructure of this type will have a non-negligible environmental impact. A “life cycle impact assessment” should be conducted life cycle assessment, Lca) of the bridge to quantify how many emissions it would produce throughout its period of use, starting from the production of materials and construction sites, and how many it would eliminate. But to date there is no complete LCA study of this type.

The second limitation of the estimate cited by Salvini concerns the hypotheses made by the two authors on the automobile transport. “In the document it is assumed that about 90 percent of the bridge’s future traffic will come from the highway and not from local traffic. But it is difficult to imagine that the bridge will be used almost exclusively by long-distance passengers,” he stressed. Green&Blue Paul Beria, professor of Transport Economics and Planning at the Milan Polytechnic. According to a report published in 2021 by the then Ministry of Infrastructure and Sustainable Mobility (Mims), about 30% of the approximately 10 million passengers who cross the Strait every year are commuters, for study or work reasons, i.e. short-distance passengers. “The hypothesis that the new bridge will generate is not taken into consideration additional car traffic compared to what already exists today,” added Beria. “A possible cost-benefit analysis of the infrastructure, which does not currently exist, would consider the increase in mobility as a benefit of the work. But at the same time more cars would be costly from an environmental point of view, due to theincrease in emissions“.

The two authors of the estimate cited by Salvini also base their calculations on a scenario in which the ferry traffic will be completely replaced by the one on the new bridge. But this is by no means obvious, as confirmed by Mollica himself a Green&Blue: once the bridge is built, some travelers could still continue to use the ferries because they are more convenient, for example in terms of journey (the project from which the government started will not directly connect Reggio Calabria and Messina) or costs. At the moment, among other things, it is not known whether the bridge will have a toll and how tall it will be. In other words, a part of the 140 thousand tons of CO₂ estimated for ferries will most likely continue to be produced.