In this day and age, the private transport is a very relevant base of the world economical sustentation: on the one hand, it brings to the people the possibility of commuting fast and flexibly to their jobs and leisure activities when they need or want; on the other, it involves a very important industrial sector which creates massive jobs around the world, either in car assemblage, in mineral prime matter obtaining and in the building of infrastructures.

Unfortunately, such a private transport system brings noteworthy problems which affect the environment and the human well-being. Health problems due to the pollution from tailpipe releases and the contribution to the greenhouse effect, as well as the progressive exhaustion of the mineral and energy resources in the Earth, are examples that demonstrate the unsustainability of the massive use of the internal combustion vehicle fed by fossil fuels.

Currently governments, automakers and mass media are frequently talking about certain new alternative fuels and technologies for automotion which, supposedly, would tackle the previously exposed problems, allowing the humanity to maintain its high lifestyle without its endemic problems. However, any person with a critic spirit will mistrust about the veracity of those optimistic theories and understand that it is only possible to get an objective point of view through a technical study of these technologies.

For this reason, along with the increasing massive social awareness on this topic, this research has been performed with the aim of compiling the necessary information to scope out the actual viability of the most interesting sustainable alternatives to the fossil fuels for automotion, taking into consideration the topics of the performance, the environmental preservation and the economic and technologic feasibility.

In order to do that, this research exposes the most relevant and interesting alternatives, classifies them under three different terms depending on their nature and analyses them according to their intrinsic proprieties (chapters 1 - 3).

•  Biofuels : Here includes the three main combustibles obtained from living matter which can be used on internal combustion engines (ICV), namely ethanol, methanol and biodiesel. To analyse them, the attention is focused on their obtaining, application and performance in the ICV.

•  Battery electric vehicles (BEVs): Under this term this research talks about the automobiles which are moved with an electric motor fed by electrochemical energy accumulators (batteries). In this topic, unlike in the biofuels one, the attention is redirected on the study of the state of the art and the characteristics of the related technologies.

•  Fuel cell vehicles (FCVs): Here are involved all the vehicles moved by an electric motor and an electrochemical device which transforms the energy from oxidation, mostly of hydrogen, directly into electricity (the fuel cell). In this last area, an analysis of the state of the art of the FCV technologies and a study of the hydrogen proprieties, obtaining and specific handling characteristics are combined.

Once the technical aspects of the previous alternative fuels are exposed the author uses this data so as to consider, in an inductive way, the particular benefits, drawbacks and requirements of a hypothetic massive implantation of each one of the anterior groups (chapter 4) in order to extract the final deductions, exposed as the conclusion of this document.

Finally this research includes a report of the survey performed in the Saló de l'Automòbil de Barcelona so as to know the opinion, acceptance and interest of the average potential car buyer about the alternative car power technologies in general.

To compile the information for this work the author has opted for consulting online information from divulging blogs, online studies and similar web pages to answer economic and social aspects; for the technical topics, bibliographic sources bought or obtained from public libraries are used, complemented and contrasted with data from online studies.