This work was carried out in search of a suitable fuel alternative to fast-depleting fossil fuel and oil reserves and in serious consideration of the environmental problems associated with the major use of fuels based on petrochemicals; research work is in progress worldwide. Researchers have been re-directing their interests to biomass-dependent fuels, which currently seem to be the only logical substitute for green development in the context of economical and environmental aspects. Renewable bioresources are available worldwide in the form of residual agricultural biomass and wastes, which can be converted into liquid biofuels. However, the process of converting, or chemical conversions, can be very expensive and not worthwhile to use for an economical large-scale commercial supply of biofuels. Hence, there is still need for souch research to be done on an effective, economical, and efficient conversion process. The objective of this review is to provide a deep overview of liquid biofuels and the present knowledge produced by scientists throughout the world.