Researchers at the Paul Scherrer Institute have developed a web tool called the Carculator that can be used to compare the environmental performance of passenger cars in detail. The program determines the environmental balance of vehicles with different size classes and powertrains, and presents the results in comparative graphics.

The entire life cycle of the passenger cars is taken into account, including the manufacture of the vehicles and the environmentally relevant emissions from driving.

Sample results from Carculator. The system will graph lifecycle impact for a range of specified powertrains, for a large number of impact categories:

• Climate change [kg CO₂-eq.]
• Depletion of fossil energy resources [kg oil-eq.]
• Depletion of fresh water reserves [m³]
• Depletion of metal resources [kg iron-eq.]
• Deterioration of the ozone layer [kg CFC-11-eq.]
• Eutrophication of non-marine aquatic environments [kg N-eq.]
• Eutrophication of non-marine aquatic environments [kg P-eq.]
• Formation of fine particles [kg PM₁₀-eq.]
• Human toxicity [kg 1,4-DC-eq.]
• Ionizing radiation [kg U235-Eq]
• Land occupation in an urban environment [m² / year]
• Natural land transformation [m₂]
• Noise emissions [Person-Pascal/second]
• Occupation of arable land [m²/year]
• Primary energy, non-renewable [Megajoule]
• Primary energy, renewable [Megajoule]
• Smog formation [kg NMVOC-eq.]
• Terrestrial acidification [kg SO₂-Eq-eq.]
• Terrestrial toxicity [kg 1,4-DC.-eq.]
• Toxicity of marine aquatic environments [kg 1,4-DC-eq.]
• Toxicity of non-marine aquatic environments [kg 1,4-DC-eq.]

The top sample above shows climate change impact; the subsequent chart shows human toxicity. Note the large impact of energy storage in the latter.

---

A recent PSI study led by environmental scientist Christian Bauer found that a battery electric car is already the most environmentally friendly option in Switzerland and many other countries, even when the manufacture of the battery is figured in.

The same research group has developed the web tool that makes the data and results of their ongoing studies accessible to both end users and the research community. The program guides the interested layperson through a selection of parameters: which type of engine should be used, gasoline-burning or diesel, for example, or one powered by natural gas, a fuel cell, or a battery.

Our tool offers a very wide range of engine types. In addition, it can differentiate between a large number of fuels: Besides the common ones, we have also integrated bio- and synthetic fuels of various origins, and we have considered future technologies such as CO₂ capture and storage in hydrogen production.

—PSI environmental scientist Romain Sacchi, who led the development of the Carculator

Besides the engine type and fuel, those who use the Carculator can also enter the size category of the vehicles to be compared, from subcompact cars to vans. The user also selects the country where the vehicles are to be used—because this differentiates the electricity mix for electric cars—as well as the year, between 2000 and 2050, when the cars will be registered. For the future, the electricity mix can also be manually entered to test the effects of different scenarios.

The tool also assesses the environmental impacts of the entire life cycle of passenger cars, including the manufacture of the body and all other components, such as batteries for electric motors.

The tool shows not only the calculation of all greenhouse gases—added together and expressed in CO₂ equivalents—but also those for the release of particulates, harmful nitrogen oxide emissions, and all of the usual environmental assessment indicators such as pollution of water bodies.

The Carculator graphically presents these values for all selected vehicles in parallel, for ease of comparison.

The Carculator also gives professionals a look behind the scenes: If the program is installed from the website, all the underlying calculations can be viewed, assessed, and even changed.

This is primarily intended for those in the research community who want to know how we did our work, and who might want to use our calculations for further studies of their own.

—Romain Sacchi

This complete transparency should prove helpful in the public debate.

Up to now, when it comes to the environmental impact of different means of transportation, arguments are still too often based on ill-founded results with biased assumptions behind them. We want to put an end to this through our transparency.

—Romain Sacchi

The Carculator was developed as part of the initiative on Efficient Technologies and Systems for Mobility of the Swiss Competence Center for Energy Research (SCCER Mobility).

Resources

• carculator: an open-source tool for prospective environmental and economic life cycle assessment of vehicles. When, Where and How can battery-electric vehicles help reduce greenhouse gas emissions? (in review) Sacchi R., Bauer C., Cox B., Mutel C. (2020) Submitted to Renewable and Sustainable Energy Reviews.