Advances in Automobile Engineering
Open Access

Fuel

There are unconventional fuels that may serve as near term major replacements for conventional mineral oil and natural gas. These include fuels from oil shale and bitumen, liquid fuels from coal, methane from methane hydrates, biofuels and the secondary fuel hydrogen. Here, these fuels will be reviewed as to their presumable stocks and life cycle wastes, emissions and inputs of natural resources. The unconventional fuels are usually characterized by a relatively poor source-to-burner energy efficiency when compared with current conventional mineral oil and gas. Apart from some varieties of hydrogen and biofuel, their life cycles are characterized by relatively large water inputs, emissions, and wastes. The unconventional fuels shale oil, bituminous oil, coal liquids, and methane from methane hydrates are based on natural resources which are practically finite. This does not hold for biofuels, but the sustainable supply thereof is severely limited when large numbers of people also have to be fed. In view of the problems associated with unconventional fuels, there is a case to consider fuel-less replacements for many fuel applications.