_{Clean mobility}

Diesel was once considered a wonder fuel – efficient, powerful and, with lower CO₂ emissions than gasoline, good for the environment. But recently the arguments against it have begun to mount. Is it clean? Is it safe? Does it have a future?

In 2015, it was revealed that some car manufacturers had cheated on diesel emissions tests, sparking a major debate about the fuel’s environmental impact. With studies linking diesel emissions to respiratory illness and cancer, calls have been made to ban diesel vehicles in several major European cities and public confidence has been shaken. Can diesel be turned around or is it the end of the road for this fuel? We ask diesel scientist Professor Thomas Koch of the Karlsruhe Institute of Technology and Julia Poliscanova, clean vehicles expert at the European lobby group Transport & Environment, for their views.

Creating Chemistry: Paris, Stuttgart and Madrid are among the cities that face the challenge of banning diesel vehicles by 2025. Are they doing the right thing?

Professor Thomas Koch: No, it’s not right to ban them. Modern diesel cars have a negligible impact on urban emissions. Regarding investment cost they may not be the right solution for every driving profile. However, in the latest generation the nitrogen oxide (NO_X) emissions issue has been solved. Under typical driving conditions, they emit far less than the new, stricter European limits permit and even less than many gasoline engines. It’s true there are older cars that are less clean. The question is now how to optimize these, which is a different issue from banning diesel technology.

Julia Poliscanova: I agree that in future clean diesel can exist, but the reality is that the current generation of diesel cars still on the market today is not clean. Their real-time driving emissions exceed the new limits. These cars will probably be on the road for another 15 years, while the vehicles with the newest technology will not be certified for sale until 2019 at the earliest. So it’s solved in the lab, but it’s certainly not solved in real life. Cities simply don’t have other options to clean up their air.
 

The two alternatives to diesel most often mentioned are gasoline and battery-powered electric vehicles. Are these better choices?

Koch: All solutions must contribute to a world of mobility, of course without any impact on people’s health. If you make many short journeys within cities, a gasoline, gasoline hybrid, or battery-powered electric vehicle is a very good solution. As soon as you drive more than 12,000 kilometers a year, diesel becomes more attractive. Provided the technology is completely neutral in terms of health, I’m open to every technology. I do not see a real difference anymore, except where the electricity is generated from a fuel source with high greenhouse gas emissions, such as coal.
 

Poliscanova: The new generation gasoline vehicles will have particle filters but they still have some emissions. By comparison, electric vehicles have zero tailpipe emissions, so it’s zero versus low emissions. In terms of the environmental impact of the electricity, a study by a Belgian university, VUB, looked into the life-cycle analysis of different electric vehicles on different electricity mixes, and compared them with the life cycle of diesel vehicles. It found that only when electric vehicles are run on electricity generated entirely from coal-fired plants are they slightly worse than diesel. As we are adding more renewable energy all the time to the energy mix, the electric advantage will continue to increase.

So do you believe an electric-only future is on the way?

Poliscanova: If policy makers want it, it would absolutely be possible to have an electric-only auto world by mid-century. In the medium term, gasoline engines are a perfect combination to first of all go to hybrid gasoline, then to plug-in hybrid, and finally to fully electric. The range issue has largely been solved – the fully electric vehicles coming on to the market this year or next all have a range of over 200 kilometers. In three years it will be over 300. The cost is decreasing and we will have electric vehicles that are pretty much fully competitive with conventional ones by the early 2020s. I think there is still one issue – that of charging infrastructure. However, we have time to solve this. I also think there’s a whole change in the way we see mobility. It’s a three-way revolution: electric, autonomous and shared. All three will be the future of mobility. In that respect, the electric engine is a perfect contribution.

For which uses will diesel continue to be an important part of the fuel mix?

Koch: For long-haul trucks, in particular, diesel engines will continue to give the best environmental balance, but also for medium and longer distance cars. For a standard sedan, the diesel is simply the better drive train, with 10 to 20 percent fewer CO₂ emissions in comparison with gasoline and less than a gasoline hybrid. Taking into consideration the complete production of diesel, from the well to the tank as well as from the tank to the wheel, the diesel engine has a lower CO₂ impact than gasoline. So we need it, that’s the message in brief.

Poliscanova: It is true, per kilometer a diesel engine is more efficient than gasoline. But in the last few years, we have seen gasoline engines catch up, and the difference in CO₂ emissions today is very small, especially for smaller cars. Diesel, by contrast, is driving the wrong kind of consumer behavior by encouraging people, especially in Europe, to buy bigger cars, thus nullifying the advantage. With trucks, diesel will continue to play a role, but long term there are other solutions. We might not have all trucks electric because of battery weight, but other options{bioInclude e-highways, where trucks are powered by overhead electric cables.

Koch: The total cost of ownership of electric vehicles is still higher than diesel. For many operating conditions, they are not competitive. Also, without gasoline and diesel’s contribution to tax income, which in Germany is about €36 billion, the battery electric vehicle would come under pressure. However, as I said, I see electric as another interesting approach which makes sense for certain uses. I would be happy having competitive battery- powered vehicles. But diesel will remain an attractive, consumer-friendly option for a very long time.
 

Government incentives and taxes make a difference to consumer choices. What would happen if the playing field were level?

Koch: If the subsidies for electric cars were reduced, this technology would definitely come under pressure. I agree that electric cars are an interesting approach, and for urban mobility pure electric vehicles do make sense to a certain extent. What governments should do is set environmental standards and let the market offer vehicles that meet those standards, rather than defining which technology we use. Diesel technology will be lifted to the next level in combination with hybridization and will be further improved. It will continue to be an attractive alternative for consumers for years, independent of the level of taxes, as well as being the most environmentally friendly way to move.

Poliscanova: In Europe, the lower taxes on diesel mean that around 50 percent of new sales are diesel cars. But if you look at markets where there is no diesel subsidy, sales are below 5 percent. In the U.S., they are less than 1 percent and in China less than 2 percent. The biggest change we would see in Europe if we were not subsidizing any fuel is that demand for diesel would drop and we would produce more smaller compact city vehicles. We don’t need more than that in European cities.

What are your final thoughts?

Poliscanova: The main minus of diesel is the complexity required to clean it up. Yes, we can add another technological solution, another exhaust after-treatment, another pipe, another catalyst, another sensor, but as such diesel is just very complicated and that makes it expensive. In comparison, electric vehicles are simple, clean and low maintenance. Also, we should consider the competitiveness issue: 70 percent of global light duty diesel vehicles are sold in Europe. The share in the U.S. and China is less than 1 percent. You cannot ignore the fact that other regions in the world aren’t going down the diesel path. My personal belief is that the future is electric.
 

Koch: I wonder why opponents of diesel technology argue by ignoring so many facts. But we do not disagree on one point: What we are doing today is not environmentally friendly – we import fossil fuel and burn it here in Europe. What we need to do instead is develop completely synthetic fuels, hydrocarbons, that are 100 percent environmentally friendly. We’ve started working on this and it is the right way forward to build on this important technology. For now, affordable diesel provides the freedom to drive quickly anywhere at any time in every weather – at minus 15 degrees Celsius or plus 40 degrees Celsius. One of mankind’s dreams.