Mitretek has developed long-term energy supply/demand models. At the Energy Frontiers International meeting held in Tucson, Arizona, in April, G. Tomlinson and D. Gray presented their latest results with respect to future transportation fuel demand.

Energy use patterns during the last 25 years give insights into the pervasive nature of the growth in transportation energy. Oil prices gyrated wildly at times during this period. As a result, the growth of total energy consumed was reduced for a time, actually stopping for a couple of years. Oil use dropped dramatically, indicating that other alternatives were quickly substituted for oil where it was practical to do so. Transportation energy use, however, maintained a steady growth throughout the period.

The percentage of oil devoted to transportation increased rapidly after oil prices rose in the late 1970s, which is why the world was able to reduce oil demand without reducing transportation. There are practical limitations to how far this trend can go because of competing demands for some of the petroleum barrel, and refinery limitations.

Mitretek has estimated future oil demand compared to Hubbert type projections of oil that might be expected to be produced from two estimates of world oil resources. The lower curve in Figure 1 is based on the United States Geological Survey (USGS) estimate of 2.3 trillion barrels. The higher curve is based on 3.2 trillion barrels, which is 1.4 times the USGS number. This is equivalent to increasing the average field recovery rate from 34 percent to 50 percent. The timing of the crunch may be argued, but unless the possibility of resource limitations is totally ignored, it is evident that the world's reliance on oil as the one and only source of transportation energy is about to be challenged. Tomlinson and Gray note that their projections of future oil demand are quite conservative compared to some. They consider it likely that the ultimate production of oil will exceed even the highest estimate shown in Figure 1. However, the technology and resources which contribute to this greater yield will play out over a long time period, and affect the tail of these curves much more than the peaks.

figure1Figure 1

Figure 2 shows the apparent demand for non-petroleum fuels for transportation using Tomlinson and Gray's more conservative projections of supply and demand. The baseline projections incorporate the basic assumption of a doubling of efficiency over the next hundred years. In personal transport, this amounts to increasing fuel mileage from the current world average in the 20-mile per gallon to the low 40-mpg range. The lower curve shows how much the projected deficit could be trimmed if light-duty vehicles could double this rate of efficiency improvement and achieve an 80-mpg standard. It was assumed that half the baseline transport demand is for light vehicles. The curves illustrate the significant role that efficiency improvements can play in reducing future energy demand.

figure2Figure 2

Table 1 lists alternatives of current interest. Discussions of alternatives do not always make a clear distinction between alternative fuels and alternative sources for the fuels we now consume. Both can reduce the world's dependence on petroleum. The rate of penetration of alternative fuels is limited by factors like customer acceptance, logistics of fueling stations, as well as resource limitations and economics. Alternative sources for conventional fuels need only contend with economics and resources.


Biofuels get considerable attention as a potential energy source because of the theoretical possibility that they could be produced and consumed with no net impact on CO2 emissions. The United States is one country with enough land to make biofuels a realistic candidate for some portion of transportation fuels. On a worldwide basis, however, Tomlinson and Gray have observed that demands for products from field and forest increase somewhat more rapidly than energy consumption as countries develop. They have projected future cereal and roundwood production based on present relationships between per capita consumption of these products and per capita energy consumption. These are shown in Figure 3. In view of the greatly increasing demand for products from field and forest for the growing world population, it is not reasonable to expect much acreage to be devoted to competing energy crops. However, advanced forms of biofuel production which are not competitive with the food and wood demand, such as algae grown in saline water in desert ponds, could be significant in the future.

figure3Figure 3

Table 2 gives estimates of heavier hydrocarbons which could be used to augment crude oil as a source of transportation fuels. Available heavy oil resources are estimated to be on the order of 600 billion barrels, about the same as conventional oil reserves credited to the Middle East. These resources are far more concentrated than oil and gas resources, residing principally in Canada and Venezuela. However, alternatives like heavy oils and bitumens are likely to come on line more slowly than conventional petroleum because of the more intensive extraction and production procedures. Shale oil resources are even larger, but are also geographically limited. Principal assets are in the United States, Brazil, Russia and Australia. Coal resources are truly enormous. These are available worldwide, including countries with high energy growth rates and limited fossil energy resources other than coal.


Tomlinson and Gray say that the availability of these alternative resources would seem to assure that we will have energy to meet our needs for the next 100 years or so, even if we continue to use the types of hydrocarbons that we now use. They conclude that:


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