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 As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources.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 since EU-legislation has been passed that requires the fraction of nonmineral origin to become minimum 5.75% of the total fuel consumption volume in 2010. This can be realised by substitutions in diesel or in petrol of any biological source; or fuel sold in the form of pure biofuel. (2007) There are only a few gas stations where E85 is sold, which is an 85% ethanol, 15% petrol mix. Directly neighbouring country Germany is reported to have a much better biofuel infrastructure and offers both E85 and E50. Biofuel is taxed equally as regular fuel. Fuel tanked abroad cannot be taxed