The driving forces for the development of alternative fuels are, on the one hand, anxiety about security of supply with oil, on which the transport sector still depends almost entirely, and, on the other hand, a reduction of transport-related emissions of greenhouse gases and air pollutants. In this respect, hydrogen and fuel cells are in competition with a number of other energy carriers and transformation technologies. For instance, hydrogen has to compete with improved gasoline and diesel engines, but also with synthetic fuels, biofuels or natural gas. With regard to drive trains, petrol and diesel engines still dominate. Besides an improvement of the efficiencies of these conventional combustion engines, there are also vehicle concepts under development, which are based on electric drives and which rely to varying degrees on batteries as a source for motion energy. Hence, this chapter briefly discusses the major alternatives to hydrogen and fuel cells in the transport sector and their characteristics.
Overview of alternative fuel options
Two thirds of today's oil use of more than 81 million barrel per day is for transportation, of which land transport for people accounts for some 55%, land transport for freight for some 35% and air transport for people and freight for around 10%. Almost 97% of road transport is fuelled by oil. The three most important targets with respect to transportation energy use, which are also increasingly favoured by policy makers around the world, are reduction of local air pollution, greenhouse gas-emissions reduction and energy security.