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Comparing GHG emissions from personal vehicles

Our analysis of GHG emissions from personal vehicles show that electric, hydrogen and biogas cars are best for climate in Norway and Sweden.

There has been a lot of debate around the actual climate benefits of low-emission vehicles, and different studies come to different conclusions. Regional variations can explain part of these differences. We wanted to see if we could conclude on this topic for Norway and Sweden, and if our findings would be robust across vehicle sizes. To find that out, we calculated emissions from manufacturing, using and scrapping cars in both countries, taking into account variables such as fuel/energy type and origin, vehicle size and weight class.

Cars come in all shapes and sizes, so to establish a representative analysis we collected data on as many vehicles as possible, from available online databases and websites. Our dataset includes more than 7800 cars running on fossil-fuel, 6 models with hydrogen, 63 hybrid, 28 with (bio)gas, and 67 electric models.

We have data on manufacturer and model, fuel type and consumption (both theoretical (NEDC) and real), on vehicle weight and class. For low-emission vehicles we also collected specific data on technology, battery size, weight, energy density and energy efficiency.

We analysed the data and established correlations between vehicles curb-weight, battery capacity, battery weight and energy/fuel efficiency. There are of course exceptions, but most vehicles follow the same trend. For example larger electric vehicles have heavier batteries, with higher energy capacity and use more energy per kilometer.

Correlation between vehicle weight and battery weight for 32 models of electric vehicles.

We categorised the vehicles and identified low-emission equivalents for most of the conventional fossil-fuel vehicles within the six weight-classes A to F. We then combined the data on fuel use and vehicle characteristics with our data on footprint for energy and materials, to calculate the life-cycle greenhouse gas emissions of each car technology.

Illustration of our findings for hydrogen cars in weight-class C in Norway

This approach takes into account the differences in GHG footprint for fuels in Norway and Sweden, and differences in use of the cars. The conclusion is similar for both countries: electric, hydrogen and biogas cars are best for climate in Norway and Sweden, provided that the hydrogen is from low-emissions sources (e.g. electrolysis or reforming with CCS).

Findings for weight-class C in Sweden, across technologies and fuel types

They worked on this project: