Petroleum, being dense liquid energy, dominates as world's transportation fuel, is said to be peaking out, then its production level will decline and the gap between demand and supply might expand year by year. In this paper, biofuel as a gap-filling transportation fuel, its potential energy volume, was investigated using various knowledge from papers, by unifying the knowledge into the same dry basis thermal energy terms. Agricultural land availability is limited. Therefore, the most important thing is to maximize land use efficiency (energy yield per hectare). It was found that sugarcane and sweet sorghum, which are suited for wet process like ethanol fermentation, and energy crops, either woods or grasses, which may be more suited for thermal process (gasification), are the most efficient feedstock in terms of biomass yield level. However, sugarcane and sweet sorghum converts only 40 % of its biomass into ethanol, while almost 100 % of energy crop biomass can be used for conversion. Therefore, it is concluded that the most efficient feedstock is energy crop either woods or grasses. Energy crops were also found to be more environmentally friendly with better water use efficiency (WUE), accompanied by C4 grasses, and better nitrogen/nutrients use efficiency (NUE), accompanied by C3 woods. In terms of land availability, 100 million ha land-scale is assumed to become available as least unit, which might be expanded up to several times. Energy crops, with their average yield of 15 t/ha, and their average energy content of some 18 GJ/t, would be resulted in some 27 EJ from 100 million ha land unit.
Comparison of combustion and gasification behavior of waste plastics with pulverized coal in blast furnace is necessary to increase the replacement rate of waste plastics to coal. The combustion and gasification behavior of these materials were observed by use of raceway hot model which simulated the lower part of blast furnace. Moreover, the reactivity of unburned char derived from these materials generated from raceway was estimated. The experimental results showed that the size of waste plastics with the same combustion and gasification efficiency of pulverized coal was almost 1 mm. CO2 gasification rate of unburned char derived form pulverized plastics with the size of less than 1.2 mm was similar to that of pulverized coal with the size of less than 0.1 mm. Thus, it was concluded that pulverized plastics with the size of less than 1.2 mm was completely consumed in the blast furnace, and furthermore, was effectively utilized as a reducing agent. On the basis of above results, the pulverized waste plastics recycling system was designed.
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.