March 2004

"Comparison of different propulsion systems in private transport
in terms of energy saving and reduction of greenhouse gases"

Study for the Bavarian State Ministry for Country Development and Environmental Questions

It is the goal of the present study to assess the reduction potential of greenhouse gas emissions from the passenger car sector through advanced conventional and alternative propulsion systems and fuels in Germany. Internal combustion engines, fuel cells and batteries are considered. Fuels assessed are gasoline, diesel, hydrogen (compressed gaseous and liquid), methanol, ethanol, natural gas (compressed gaseous and liquid) and electricity (battery).

The fuel consumption during vehicle operation is assessed ("Tank-to-Wheel") as well as the greenhouse gas emissions over the entire fuel production and supply chain ("Well-to-Tank", including production, transport and distribution). From these data, the greenhouse gas emissions per kilometer driven are being deduced ("Well-to-Wheel"). In addition, an analysis is being made of the greenhouse gas emissions during the production of the vehicle, which are subsequently added to the "Well-to-Wheel" emissions. The effect of different driving cycles on fuel consumption are analyzed.

The potentials for the availability of renewable energies for the production of car fuels in Germany and Europe are assessed. In addition, some analysis is made of the possible speed of renewable fuels.

The results are presented in detail and evaluated according to various criteria. The potential contributions to greenhouse gas emission reductions of the different propulsion systems and fuels are presented in scenarios and compared to the CO2 reduction goals.

The main boundary conditions under which alternative fuels are being discussed are presented: climate change, availability of fossil energy resources as well as political and industrial greenhouse gas reduction goals.

A detailed chapter compiles the present knowledge on hydrogen safety and acceptance.