Fuel were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has an energy density of 10–20 MJ/kg. Recently biofuels have been developed for use in automotive transport (for example Bioethanol and Biodiesel), but there is widespread public debate about how carbon efficient these fuels are. Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), formed from the fossilized remains of ancient plants and animals by exposure to high heat and pressure in the absence of oxygen
Ethanol fuel by country the largest and most successful bio-fuel programs in the world, involving production of ethanol fuel from sugarcane, and it is considered to have the world's first sustainable biofuels economy. In 2006 Brazilian ethanol provided 18% of the country's road transport sector fuel consumption needs, and by April 2008, more than 50% of fuel consumption for the gasoline market. As a result of the increasing use of ethanol, together with the exploitation of domestic deep water oil sources, Brazil reached in 2006 a volumetric self-sufficiency in oil supply, but is not effectively self-sufficient, since most of its locally extracted oil is