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| Fig. 1: Estimated platinum demand due to fuel cell vehicles in 2010 to 2050. The penetration ratio of fuel cell vehicles and platinum load per car used in this calculation are also shown with the right y-axes. Estimated platinum demand in 2010 to 2050. |
The availability of platinum is an important problem in energy for transportation. Currently the automobile industry is the major consumer of platinum, accounting for 41% of the world demand in 2002. [1] In hydrogen fuel cells, platinum is an essential catalyst to drive oxidation of hydrogen to water. Thus the price and availability of platinum has a major impact on the driving force for transportation. In this report, current usage and production of platinum is reviewed, and a prospect of future platinum supply versus demand is discussed.
Platinum is a rare metal. Unlike other minerals, platinum is largely concentrated around a single geographical location in South Africa; among total 14 million ounces of platinum produced in 2002, 57% was produced in South Africa, followed by 31% in Russia, and lesser amounts in the United States and Zimbabwe. [1]
The Bushveld Igneous Complex (BIC) in South Africa is the world's largest platinum mine. BIC was formed around two billion years ago, when a large amount of molten rock from the Earth's mantle was brought to the surface. [2] As the magma slowly cooled on the Earth's surface, different minerals solidified and accumulated in parallel layers due to different melting points, including an ore called chromite which contains Pt.
The first challenge in predicting the future platinum budget is to estimate the demand. The demand from the fuel cell vehicle sector is a function of platinum loading per car and the number of fuel cell vehicles. There are, of course, other sources of demand, mainly the jewelry industry and the diesel catalytic converters. In this report, we assume that the demands from these sectors stay constant over time, and focus on the changes the introduction of fuel cell vehicles imposes.
The platinum loading for fuel cell stacks keeps decreasing due to advancing technologies. [3] It was expected to fall from about 20 ounces per car in 1990 to 1 ounce per car by 2010, and ultimately to reach 0.2-0.3 ounces per car. [4] So it is more reasonable to assume these low levels to estimate the future demands. One realistic scenario proposed by the Oakridge National Laboratory is to assume that 5% of new car sales in 2020 have fuel cells, 20% in 2030, 80% in 2040 and 90% in 2050, and that the total sales of cars worldwide increases by 45% per decade from a 2000 figure of 48.7 million vehicles per year. [5] Using these parameters, one can calculate the estimated platinum consumption.
Fig. 1 shows the result of this calculation. When we integrate the plot in Fig. 1, the total amount of platinum needed in the next forty years from 2010 to 2050 sums up to 700 million ounces.
The second task is to estimate how much platinum is left on the earth. Mining companies quote various "reserve" numbers on their reports and websites. "Reserve" is actually a well-defined term and it is important that we understand what it means; it is
In other words, ores that are known to exist cannot be reported unless these issues are addressed. Therefore the platinum "reserve" must be distinguished from the amount of platinum that is left on the earth."an ore body for which adequate information exists to permit confident extraction. Briefly, it requires that all aspects including adequately spaced drilling, assaying, mineralogical and metallurgical studies, mine planning, beneficiation, environmental, social and legislative issues, and financial viability have been addressed." [6]
On the other hand, "deposit" is a term that means the amount of the ore that exists in a particular area. The mining companies usually do not publish deposits. Deposits are of concern more than ten to twenty years ahead, and are also much more difficult to calculate. Cawthorn attempted to estimate such "deposit" of platinum in BIC from a purely geological perspective based on the simple assumptions. [6] This calculation starts with the relatively well known geographical and physical parameters in Table 1.
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| Table 1: The geometric parameters assumed to calculate deposit in Bushveld Igneous Complex. |
From these numbers we find that the weight of platinum per 1 km depth is
| L d t ρ α sin( θ) |
= | 3.5 × 108 ounces |
There are 350 million ounces of platinum per 1 km of vertical mining depth. Assuming that mining at the depth of two kilometers is straightforward, because there are other platinum mines operating at more than two-kilometer depth, there are at least 700 million ounces of platinum that can be mined in BIC. This amount is just about enough to cover the 700 million ounces for the next forty years estimated in the previous section, excluding any other demands such as jewelry or diesel converters.
Based on the scenario presented in this report, the physical amount of platinum existing on the Earth is barely enough to cover the world demand in the next forty years for fuel cell vehicles. It is important to note that the scenario of the fuel cell penetration can change, and the demand estimate can change significantly depending on that. Many different scenarios were found, while this report attempted to choose the most conservative values. If the predicted parameters were reasonable, platinum will run out, and recycling of used platinum will be necessary. Moreover, the fact that the platinum deposit is so concentrated in one region can also be problematic; it may pose the same, if not worse, political problem that the crude oil production has at present.
© 2010 Takane Usui. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] H. E. Hilliard, "Platinum-Group Metals," U.S. Geological Survey Minerals Yearbook.
[2] H. V. Eales and R. G. Cawthorn, "The Bushveld Complex," in Layered Intrusions, ed. by R. W. Cawthorn (Elsevier,1996).
[3] " Fuel Cells Gearing Up To Power Auto Industry," ScienceDaily, 31 Oct 07.
[4] S. Potter, "Transport Energy and Emissions: Urban Public Transport," in Handbook of Transport and the Environment, ed. by D. A. Hensher and K. J. Button (Elsevier,2003).
[5] "The Impact of Increased Use of Hydrogen on Petroleum Consumption and Carbon Dioxide Emissions," U. S. Energy Information Administration, SR/IOAF-CNEAF/2008-4, August 2008.
[6] R. G. Cawthorn, "The Platinum Group Element Deposits of the Bushveld Complex in South Africa," Platinum Metals Review 54, 5 (2010).