Meglio il treno o l’aereo?
Sto programmando un viaggio a Amsterdam, in Olanda. Da bravo ecologista, mi era parsa una cosa buona quella di usare il treno invece dell’aereo. Bene, mi sono dovuto ricredere, perlomeno in termini di prezzo. In treno, Firenze-Amsterdam sono 22 ore di viaggio che mi costano circa 350 euro, anche in seconda classe. In aereo, sono un paio d’ore di viaggio per un costo totale di 250 euro circa, nella classe più economica. Non c’è paragone – l’aereo batte il treno sotto tutti i punti di vista, eccetto che per le varie umiliazioni alle quali ti costringono al check-in.
E’ solo una questione di prezzi? No, sembrerebbe proprio che l’aereo consumi meno energia del treno. E’ arrivato recentemente da Berkeley uno studio interessante che compara tutto il ciclo di vita delle emissioni di vari tipi di veicoli. I calcoli di “ciclo di vita” includono tutti i fattori che richiedono energia per un certo tipo di tecnologia. Ovvero, in questo caso, vanno oltre il semplice calcolo di quanto un certo veicolo consuma per chilometro.
I risultati? In molti casi, viaggiare in aereo risulta in emissioni minori che in treno e sicuramente molto minori che in macchina. Risultato che rimarrà valido finché i combustibili fossili rimangono predominanti rispetto alle rinnovabili.
In sostanza, per non emettere niente, è meglio stare a casa, ma se proprio devo andare a Amsterdam è meglio che ci vada in aereo.
___________________________________________________________
http://www.newscientist.com/article/dn17260-train-can-be-worse-for-climate-than-plane.html?DCMP=OTC-rss&nsref=online-news
Train can be worse for climate than plane
True or false: taking the commuter train across Boston results in lower greenhouse gas emissions than travelling the same distance in a jumbo jet. Perhaps surprisingly, the answer is false.
A new study compares the “full life-cycle” emissions generated by 11 different modes of transportation in the US. Unlike previous studies on transport emissions, this one looks beyond what is emitted by different types of car, train, bus or plane while their engines are running and includes emissions from building and maintaining the vehicles and their infrastructure, as well as generating the fuel to run them.
Including these additional sources of pollution more than doubles the greenhouse gas emissions of train travel. The emissions generated by car travel increase by nearly one third when manufacturing and infrastructure are taken into account. In comparison to cars on roads and trains on tracks, air travel requires little infrastructure. As a result, full life-cycle emissions are between 10 and 20 per cent higher than “tailpipe” emissions.
Mikhail Chester and Arpad Horvath of the University of California, Berkeley, included in their calculations data on the “life expectancy” of each component of each mode of transportation, such as the tracks used by a train and the airports used by aircraft.
They calculated the total “travel kilometres” each component allows and how many tonnes of greenhouse gases were emitted to build and maintain each component. This allowed them to calculate the component’s emissions per kilometre travelled, for each mode of transport per kilometre for each traveller on board.
Empty seats
Cars emitted more than any other form of transport with the notable exception of off-peak buses, which often carry few passengers. Passengers on the Boston light rail, an electric commuter train, were found to emit as much or marginally more than those on mid-size and large aircraft. This is because 82 per cent of electricity in Massachusetts is generated by burning fossil fuels.
The researchers found that travelling 1 kilometre on a nearly empty bus during off-peak hours emits eight times more per person than taking the same bus at rush hour – suggesting peak-time commuters may suffer, but they do less harm to the environment.
The occupation level of a vehicle is an important but often-overlooked factor, says Chester. “Although mass transit is often touted as more energy efficient than cars, this is not always the case.” Buses turned out to be the most sensitive to how full they were – those with only five passengers were less efficient than cars; even large SUVs and pick-up trucks.
Clearer view
The results make it easy to target attempts to cut emissions and could change how politicians think about measures to improve transportation, say the researchers.
The life-cycle emissions generated by cars, buses and aircraft are dominated by tailpipe emissions pumped out in day-to-day running of their engines. Hence, the best way to reduce emissions from these modes of transportation would be to increase fuel efficiency and push for renewable fuels.
Crisscrossing the US with a rail network, however, creates a different problem. More than half of the life-cycle emissions from rail come not from the engines’ exhausts, but infrastructure development, such as station building and track laying, and providing power to stations, lit parking lots and escalators
Any government considering expanding its rail network should take into account the emissions it will generate in doing so, Chester says. Setting up a public transportation system that only a small proportion of the population uses could generate more emissions than it cuts, he adds – especially if trains and buses are not well connected.
“New rail systems should serve as links to other transit modes, as is often the case in Europe and Japan,” he says. “We should avoid building rail systems that are disconnected from major population areas and require car trips and parking to access.”
Transport studies expert Abigail Bristow of Loughbourough University, UK, says the paper is valuable because it attempts to compare transport on equal terms. “The conclusion that rail emissions are best reduced by reducing the use of concrete in station construction is a nicely different perspective that a purely transport oriented analysis might have missed,” she says.
