Diesel Cars Emit More Greenhouse Gases Over Full Lifecycle Than Gas/Petrol Cars (Study)

21 Sept 2017 by  in Clean Technica

Contrary to common political arguments for their use, diesel cars are actually responsible for more greenhouse gas emissions over a full lifecycle basis than gas/petrol cars are, according to a new analysis from Transport & Environment.

As much research has already shown, of course, diesel cars are also responsible for higher particulate matter and NOx emissions than petrol/gas cars are.

So, not only are diesel cars responsible for the release of disproportionately high levels of dangerous air pollutants, but they also release more carbon dioxide than petrol cars as well — despite the whole selling point of the diesel car scam being that they could be used to help prevent extreme anthropogenic climate warming.

Going by the Transport & Environment (T&E) analysis, an average diesel car is responsible for around 3.65 tonnes of carbon dioxide emissions more over its full lifetime than an equivalent gas/petrol car is.

This is primarily due to the presence of heavier and more complex engines; a more energy-intensive fuel refining process; the inclusion of biodiesel in blended fuels (with biodiesel being responsible for high emissions in its creation process); and also due to higher mileage counts resulting from lower fuel costs.

Green Car Congress provides some information on the methodology and assumptions of the analysis: “The average gasoline lifetime driving distance of 175,000 km (108,740 miles) is taken as the starting point. The average diesel car is driven longer, however, only 4% of this is due to the lower fuel price (rebound effect). T&E adds an additional 7000 km (4,350 miles) to the diesel lifetime distance to account for this.

“T&E used the latest real-world fuel consumption figures for diesel and gasoline: 6.3 l/100 km (37.3 mpg US) and 7.1 l/100 km (33.1 mpg US), respectively. To account for biodiesel effects, T&E assumed a conservative estimate of 5% biodiesel content. The composition of the biodiesel itself uses the average shares of rapeseed oil (48%), palm oil (27%), waste oils (15%), soya oil (5%), tallow & grease (4%), etc. Similarly, a 5% bio-blend is assumed in gasoline for consistency, using the EU average shares taken from ePure: corn (38%), wheat (37%), sugars (14%), etc. The carbon intensity of both biodiesel and ethanol is derived by adding ILUC values (the Globiom EC study) to the direct carbon intensity of different feedstocks.

“Extra manufacturing emissions are taken to be 5% of the average 5 tonnes of CO2. For diesel and gasoline shares of B7 and E95, diesel and gasoline specific densities, energy contents and JRC-derived overall well-to-wheel (WTW) carbon intensity factors are used.”

Interestingly, the new analysis also explores the reasons for Europe’s abnormally high diesel car market penetration rate. As some of those reading this are probably aware, while diesel cars possess a roughly 50% market share in Western Europe, elsewhere in the world they are truly a niche product — making up less than 1% of new vehicle sales in the US, and less than 2% of new vehicle sales in China.

So, what were the reasons identified in the new analysis?

The three primary reasons, according to Transport & Environment, have been:

1. The presence of heavily distorted vehicle and fuel taxes in many countries. In many countries in Western Europe diesel fuel is apparently taxed between 10% and 40% less than petrol/gasoline is. This represents around €32 billion in lost revenue in 2016 alone, according to Transport & Environment.

2. The existence of slanted European Union emissions standards that have over the last few decades allowed diesel cars to legally emit considerably more NOx that petrol/gas cars can. This problem is exacerbated by the use of easily gamed testing processes and “ineffective” (at the best) regulatory oversight of the industry.

3. The use of “biased” carbon dioxide regulations, which result in weaker targets being set for auto manufacturers that offer larger and heavier diesel cars.

That all sounds pretty accurate to me. Though, I’d say that it probably doesn’t really draw as much attention to the issue of corruption within the regulatory bodies charged with oversight of the auto industry as is deserved. With the degree of corruption that’s currently present, how is it even possible for effective action to be made on that level?

Regardless of regulatory corruption, though, those of us who don’t want to breathe diesel fumes can make our opinions known by not buying cars from the companies that sell them, and by sharing articles like this one. In other words, rather than simply not buying diesel cars yourself, boycott the companies completely, and transition to firms/brands that aren’t involved in the market at all.

Something else to note: many cities now seem to be moving toward the outright ban of diesel cars — London serving as a good example — because of the deadly air pollution associated with them. So, while national and EU-level regulatory bodies may be too inept to do anything about the problem, that doesn’t matter too much, because city-level bans are politically possible and likely to sound the death-knell for the market even without help elsewhere. It may be prudent, that being the case, to let your local government know your opinion on the matter and to draw attention to successful bans elsewhere.

For more information on the diesel car air pollution problem, see:

60-Million-Strong Study Shows Clear Link Between Exposure To Air Pollution & Premature Death

Euro 6 Diesel & Petrol Cars Exceeding Legal Emissions Levels During Real-World Use, ICCT Study Finds