How bad is Diesel?

Great summary. Though it would be nice if our cities were designed better, so that more households could go car-free, or even from 2 cars to one. That's what I'd really like to see. Even electric cars produce particulate emissions from the wear on the tires, asphalt, and brakes.

I never knew about the mix of particulates, very interesting. The whole video is a brilliant breakdown.

I like this type of reporting; it's based on verifiable studies, not on gut feel. Thank you.

As an Emission Engineer for a US Heavy Vehicle OEM - you mentioned DPF's required since 2007 in North America but you neglect mentioning SCR's required since 2010 in North America. Also, if you really want to see very high emissions, look at ships; cruise and freight and locomotives. Ships burn the heavy bunker oil that is very high in sulfur, and trains to my knowledge have no emissions reduction systems installed yet here in the US. DPF = Diesel Particulate Filter Also, you are correct that a regeneration occurs in the DPF to change the collect soot to ash, but at some point they need to be cleaned of the accumulated ash. FSX out of Washington State makes some very good equipment to clean the ash from the DPF's. This can be sold to cement companies! SCR = Selective catalytic reduction These are after the DPF and use DEF (Diesel Emissions Fluid: Urea) to react in the SCR to change the Urea to Ammonia which then changes the NOx's to harmless Water and N2. To keep the negative sulfur reactions, low sulfur fuel has been required since 2007 in North America. However, the emission regulations from CARB are getting more and more onerous, CARB is openly admitting they are now using these regulations to remove ICE vehicles from the roads. At this point it has little to do with reducing emissions. My German relatives were always bewildered that we in the US were ahead of them in emissions reductions. I still have my 2004 Jetta TDI that on one trip cross county got 56 mpg with two people and 3 dogs.

I’m an Aussie and I drive a V8 turbo diesel… it has a 170L long range fuel tank. Driving economically I can stretch a full tank to almost 1000km. When a common highway sign for us is no fuel for the next 2, 3, 4, 5 hundred km. This isn’t because the service stations are out it’s because they don’t exist. A common sight here is petrol cars with several fuel cans strapped to the roof not because the fuel was cheap it’s because they don’t have the range they need to get to the next fill point. Obviously I live in a very remote area and the cities are much better suited to cleaner or “greener” options.

What a superb explanation. Sabine should should be applauded as an excellent science communicator.

1:39 I have a similar story. During the mid 70's my family had a Ford Pinto. When the emissions were suddenly tightened, the only way the car could pass (it was a 1974 model that used leaded gas) was for my father to tweak the carburetor to such a lean mixture the engine barely ran. Once the car passed inspection, he'd restore it back to a mixture the car could run on.

I was a mechanic in Germany, so I learned a lot about cars and how they work, especially since I went to a Berufsschule for 3.5 years to do it. With that being said, while diesel might seem tempting at first, I can, in good conscience, only recommend it if you make long trips regularly, or have a relatively long daily commute (say 200 km one way). For everything else, petrol is the way. Why? Because of carbon build-up inside of the engine. This actually correlates to the emission of soot particulates out the exhaust. Engines using Direct Injection (virtually all diesel engines, and some petrol engines) produce particulates of different sizes, depending on the compression ratio. Ergo, diesel -> bigger particulates, gasoline DI (or GDI) -> smaller particulates. Engines using single point or multipoint (port) injection emit no particulates, because the fuel has more time to mix with the air within the intake manifold. DI engines also have more carbon build-up on the intake valves, that is accelerated when driving for short distances frequently, and not allowing the engine to reach its operating temperature. Non-DI engines do not suffer at all from this, since fuel droplets that land on the hot intake valves evaporate quickly and act as a kind of steam cleaning, preventing build-up altogether. As a technician, electric vehicles are my absolute favourite. Over 98% efficiency, regenerative braking, instant torque, no more oil changes, the brakes last much longer... Really, apart from the battery technology, there are no downsides. Barring cost, mild hybrids are a good compromise between the efficiency of an electric motor and the energy density of fossil fuels, and you don't even have to plug it in. Gasoline would be the most sensible choice if you make short to medium trips, and even the occasional road trip. As previously stated, I would only ever consider buying a diesel if I know I'm going to travel long distances frequently.

I am a Diesel fan! It works just efficient and compared to old Diesel engines, it has improved a lot.

There’s a solution space, depending on your actual requirements - average distance travelled per day, average travel speed, maximum range and load. If you want to optimise for minimum GHG emissions and an EV is too costly, select the lightest vehicle that fits you daily load requirements. Then select an engine size that suits you average travel speed (air drag increases as a function of velocity squared). Generally, a smaller engine capacity can operate more frequently in its maximum efficiency region. Large capacity is needed only to haul high loads or travel at high speed. Some engines can turn off fuel flow to individual cylinders to optimise fuel efficiency based on load. Turbocharging increases effective engine capacity and efficiency. Last year I purchased a small passenger hatchback vehicle with a turbocharged petrol engine - this suited my urban use with an average speed of 33km/h (mostly 60km/h with traffic stops), and about 5k km per annum. I wouldn’t sweat about finessing the solution too much, you can achieve major GHG reduction cheaply by changing your usage, i.e. work from home more, plan travel to reduce redundant trips, accelerate smoothly to keep the engine operating efficiently, use detachable roof racks to reduce drags when not in use, regular maintenance to ensure the engine is operating correctly, etc… Good luck finding a vehicle - global supply is lower than demand, so prices are high and choice is limited. BTW, in Australia only 25% of new sales are passenger vehicles - like the US, we seem obsessed with SUV, 4x4WD and light trucks. Go figure…

Would be interesting to see the comparison of the amount of particulates produced by engine, tires and brakes.

Just when you think you are beginning to understand a problem, you discover another variable that affects the response properties you are studying. Asbestos particle size is important since it interacts with the lungs much more detrimentally at a certain size, but like Sabine mentioned the surface area and/or aspect ratio can be a contributing factor. Then add in synergistic correlation coefficients with other contaminants and you need a computer to understand what tail is wagging the dog.

What you did not mention is the effect of range you drive typically, and the outside pressure/altitude. It takes a decent diesel engine approximately half an hour (30-60km) to reach its best performance temperature. Most drives are much shorter. Than a decent gasoline engine wins. On the long run (>500 km) the diesel wins, given a scr technology using a small amount of urea (DEF) and a good particulate filter and filter recycling cycle. Already at 1000m altitude normal diesel performance goes down considerably and no (thermodynamica) advantage remains. I use a gasoline engine for short distances (~50km) and an diesel for the long ones (1000 km/dag) . Gasoline engines are earlier at best operating temperature but emit gasoline by incomplete burning in the first 0-10 minutes, particularly on “stationary “ conditions (traffic jam in /around cities.. So, walk and bike in the cities, use a gasoline engine for short trips (50 km), and a decent diesel for the long drives (>100 km). My own “experimental data” on 40 years of driving on request..

Several years ago, it was finally recognized that the actual largest source of air pollution in southern California was no longer cars, but actually the Port of Los Angeles. As a result, they have been trying to ban the burning of "bunker oil" within so many miles of the coast, and requiring ships to hook up to grid power instead of running their APUs.

Thank you for this objective presentation! Add blue (I.e. urea) injection on exhaust catalyst on modern Diesels can reduce 90% NOx. This makes gasoline and Diesel engines comparable, at least from NOx emission perspective. I was in the same situation as you, just bought a new Diesel car with Addblue, as I use it only for long distance journeys.

Problem with the particulate filters is that they get clogged unless the car is regularly drives fast for a longer distance. Which will not happen in city driving. Hence some owners remove the filter :( which then had the result that authorities are blocking all diesel cars in some areas.

I remember reading a study 2 years ago during covid lockdowns, which analyzed the relationship of traffic in cities with air pollution. They showed that even during lockdown with vastly reduced traffic, the values of air pollution (NOx and fine particles) did not correlate at all with the amount of cars and trucks driving in the cities. The study suggested that other meteorological phenomena play a much stronger role than was previously thought.

Nice video. Realize that the emission standards (Euro 6d) at this moment are so strict that it hardly makes any sense to make them any lower ( PM 0.005 and NOx 0.08 g/km) however politicians think that they contribute something to the air quality when they make it almost impossible for the car manufacturers to fulfill these requirements

My worry is less about what is created by the exhaust and more about the environmental cost around the entire process to make a vehicle.

Sabine I would love for you to do an in depth analysis for forest fire, greenhouse gases and pollutants. This is especially a problem in the western US. It is a much much bigger problem and one that can easily be eliminated. There are a few (very few) rapid response aircraft that have shown to be extremely effective, yet they are often not allowed to put out fires early, or at all in National forests, due to bureaucracy and turf power struggles.