Smog is Forcing France to Rethink its Love of Diesel

Last week, the smog in Paris got so bad, city officials made public transit free and banned half the city's cars from the road. The vehicle ban only lasted a day, with the reduced traffic and changing weather patterns alleviating the smog situation. But why did the smog get so bad in the first place? Blame France's long love affair with diesel-powered vehicles—an affair the country will probably have to end, or at least modify, to prevent further smog emergencies.

Why does France love diesels? Basically, because they're cheap to drive. A diesel-powered engine generates more torque, or twisting force, than a comparably-sized gasoline-powered engine. That means the diesel burner doesn't have to work as hard to get your car down the road, resulting in a 20 to 40 percent boost in fuel economy on average.

There's another incentive for French buyers to choose diesel vehicles: thanks to a longstanding subsidy, diesel fuel is usually about 15% cheaper than gasoline in France. So, even if a new car costs more when optioned with a diesel engine, there's a solid chance a buyer will come out ahead on running costs. Now you see why about 70 percent of new cars sold in France are diesel powered.

(Why don't we love diesels in the U.S.? Some of us gearhead weirdos really, really do. But the general car-buying public, turned off by the half-baked, slow, smelly, unreliable diesel cars sold here in the 1970s and 80s, doesn't seek them out, and most manufacturers don't bring them to our shores. When they do offer diesel models, they sell in small numbers, and the fuel efficiency benefit is somewhat negated by U.S. diesel prices running significantly higher than gasoline. Right now, diesels only make up about three percent of the non-commercial vehicles on U.S. roads.)

So French drivers like to save money. Admirable. But they're ruining the air quality in France.

The dirty downside of diesel-powered vehicles is emissions. While more fuel-efficient diesels put out less carbon dioxide than comparable gasoline vehicles, they generate much higher quantities of nitrogen oxides, which react in sunlight to form harmful ground-level ozone and smog. Diesels also generate particulate matter, microscopic soot particles that irritate airways and are known to cause cancer and other diseases. There's also evidence that diesel exhaust is messing with bees. The horror.

Of course, many countries have put new emissions regulations in place to cut down drastically on these types of emissions, and manufacturers are scrambling to make sure their diesel offerings meet the new laws. But the average vehicle on the road in Europe is nearly 10 years old, and even a perfectly maintained older vehicle will put out more emissions than a brand-new car.

Add up all those factors—France's love of diesel-powered vehicles, an aging fleet of cars on the road, and weather that kept the resulting smog parked right on top of Paris, and you've got the situation Parisians saw last week. Chances are, it's not the last time this will happen.

So what's the solution? French lawmakers have suggested ending the country's diesel fuel subsidy even before last week's air emergency. Now that the smog is on everyone's mind (and a mayoral election is just around the corner), politicians are coming out strong against diesel—mayoral front-runner Anne Hidalgo has even vowed to eliminate diesel from Paris entirely.

That's probably going to be a hard sell. Already, Paris has put 320 new diesel-powered public buses in service this year, unlike other cities that have switched to cleaner buses powered by compressed natural gas. If France wants to clean up its act, it's going to have to do something about its diesel predilection.

Image credit: AP Photo/Jacques Brinon