<P> The production of ethanol from sugar cane is more energy efficient than from corn or sugar beets or palm / vegetable oils, particularly if cane bagasse is used to produce heat and power for the process . Furthermore, if biofuels are used for crop production and transport, the fossil energy input needed for each ethanol energy unit can be very low . EIA estimates that with an integrated sugar cane to ethanol technology, the well - to - wheels CO emissions can be 90 percent lower than conventional gasoline . </P> <P> A textbook on renewable energy describes the energy transformation: </P> <P> Presently, 75 tons of raw sugar cane are produced annually per hectare in Brazil . The cane delivered to the processing plant is called burned and cropped (b&c), and represents 77% of the mass of the raw cane . The reason for this reduction is that the stalks are separated from the leaves (which are burned and whose ashes are left in the field as fertilizer), and from the roots that remain in the ground to sprout for the next crop . Average cane production is, therefore, 58 tons of b&c per hectare per year . </P> <P> Each ton of b&c yields 740 kg of juice (135 kg of sucrose and 605 kg of water) and 260 kg of moist bagasse (130 kg of dry bagasse). Since the lower heating value of sucrose is 16.5 M J / kg, and that of the bagasse is 19.2 MJ / kg, the total heating value of a ton of b&c is 4.7 GJ of which 2.2 GJ come from the sucrose and 2.5 from the bagasse . </P>

Where does sugar come from in the world