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 As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources.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 first flex motorcycle was launched to the market by Honda in March 2009, and a second model in September 2009. By the end of 2009, both Honda flexible-fuel motorcycles had sold a total of 183,375 units, representing an 11.4% market share of the Brazilian new motorcycle sales in that year. Two other flex-fuel motorcycles manufactured by Honda were launched in October 2010 and January 2011. During 2011 a total of 956,117 flex-fuel motorcycles were produced, raising its market share to 56.7%. Cumulative production of the four available flex fuel models since 2009 reached 1.48 million units in December 2011.