Abstract
Bio-transportation vehicle fuel, including bio-diesel from oil-seeds, 1st generation bio-ethanol from starch or sugar, 2nd generation bio-ethanol from ligno-cellulosic biomass, and gasification products including FT-diesel and methanol were unified into the same language, which is, "number of vehicles covered by the fuel per hectare" by using relevant information. In terms of vehicles, both ICEs (internal combustion engines) and FCVs (fuel cell vehicles) were investigated. Although, hydrogen can also be converted from biomass, hydrogen was excluded from this evaluation. Because hydrogen is a secondary energy like electricity, and is not a liquid fuel, therefore, it is too difficult to evaluate on the same basis, especially from infra-related point of views. To this end, world transportation fuel usage was evaluated focusing on vehicle fuel economy on average. Then relative vehicle fuel economy data among different biofuels were used to unify the language. The results clearly indicated that methanol in the FCV application (on-board reforming into hydrogen) turned out to be best with some 3.0 vehicles per hectare (300 million vehicles from 100 million ha), followed by methanol in the ICE application with some 1.8 vehicles per hectare. Energy input during conversion is found to be highest in the 2nd generation bio-ethanol with 0.635 GJ/GJ-fuel fossil-basis, followed by the 1st generation bio-ethanol from starch with 0.535 GJ/GJ-fuel, then, bio-diesel with 0.38 GJ/GJ-fuel. On the other hand, 1st generation ethanol from sugarcane is found to be exceptional and near zero input due to bagasse energy use. In terms of methanol, depending on how much electricity is required in its process design, its energy input ranges from between near zero to 0.25 GJ/GJ-fuel fossil-basis. The results of the investigation clearly suggest that methanol from energy crops to be used in onboard methanol fuel cell vehicles is the best option in terms of maximum number of vehicles covered by biofuel and less energy input during energy conversion. In the event of more severe limitation in both petroleum and land availability in the future, it is more likely that the best option would be selected worldwide, which is methanol - FCV route in this evaluation.
