5. Hydrogen, ammonia, alternative fuels and zero-emission engines

5.1 Biofuels and renewable resources

A wide variety of fuels can be used to power combustion engines, from plant, animal and even mineral sources. While many of them can be obtained from renewable sources, particularly those of plant and animal origin, the question of the sustainability of these resources is becoming increasingly critical [BE 8 550] .

With first-generation biofuels obtained by trans-esterification of vegetable oils, or by fermentation of sugars, fuel production competes...