• Overview
  
  
• Overview: Conventional Oil
  
  
• Conventional Oil: Simple Estimate
  
  
• Conventional Oil: More Realistic Estimate
  
  
• Overview: Natural Gas
  
  
• Natural Gas: Simple Estimate
  
  
• Overview: Coal
  
  
• Coal: Simple Estimate
  
  

In 2001, the fossil fuels -- oil, natural gas, and coal -- provided 86% of the energy that is “consumed” [1,2] by all the people of the world. The International Energy Outlook 2004 (IEO 2004), published by the United States Department of Energy (USDoE), contains a projection that, in 2025, fossil fuels will provide 87% of the energy consumed globally. It is important to note that the authors of the IEO 2004 also project global energy consumption to increase by an average of 1.8% per year from 2001 to 2025.

Historically, finite fossil fuel resources are consumed in the following way. To begin, the fossil fuel is not yet discovered, and therefore the consumption rate is zero. Then the fuel is discovered and consumed at an increasing rate as the fuel achieves widespread use and as the will and the technology to discover more of the fuel increases. Finally, the fuel is depleted, and the consumption rate must necessarily fall to zero. An example of such a discovery/consumption/depletion cycle is provided by anthracite coal from Pennsylvania. [3] The time interval that begins and ends when the consumption rate is approximately one-third of its maximum value may be taken to be a rough measure of the "lifetime" of the fossil fuel resource.

Because modern society depends on the fossil fuels, it is of great interest to gain a feel for the “lifetime” of the fossil fuels -- that is, the number of years it will take to consume the known reserves of each kind of fossil fuel. It is important to remember that consuming all of the known reserves does not mean that all of the fossil fuels will be "gone"; there will always be some amount of fossil fuel in the earth. However, the "lifetime" provides an estimate of how much longer the fossil fuel will be available (economically and physically recoverable). Some petroleum industry analysts think that the "lifetime" is not as important as the date of peak production, which occurs approximately half-way through the "lifetime".

The calculations that you can perform by using the web pages linked to this page (see the menu at the left) are meant to help you gain a feel for the "lifetimes" of the fossil fuels. There are two methods used to estimate the "lifetimes": a simple method, in which the annual percentage change in consumption is assumed to be constant for all time; and a more realistic method, in which the consumption rate is assumed to smoothly rise to a peak and then smoothly fall (eventually) to zero. These methods are implemented on the pages listed on the menu on the left. These pages enable you to change various inputs, such as the amount of remaining fossil fuel reserves, the rate of consumption, and the annual percentage change of the consumption rate.

NOTE: To use these pages, you must be using a browser that enables Java to JavaScript communication. PC users using Internet Explorer or Netscape Navigator 7.0 will probably experience no problems. Mac users: OS 9.1 with Netscape 7.0 is known to work. It is likely that OS X with any latest-edition browser will work, but the author has not tested these configurations.

Because world events can significantly alter the rate of consumption, no claim is made about the accuracy of the predicted "lifetimes". Please keep in mind that it is most useful to simply allow the numbers to vary and see how the "lifetime" of the fossil fuel changes.

Estimates of remaining reserves, consumption rates, and projected consumption rates are provided on each page to inform the user of the latest information from the U.S. Department of Energy that could be found by the author.

You are encouraged to try different inputs to obtain different "lifetime" estimates. It is worth wondering whether it is reasonable to assume large reserves when planning for the energy future.

Do you think national energy policy should be set by assuming the best case (large reserves) or the worst case (small reserves)? What are the consequences if the assumption of large reserves proves to be wrong, and planning is based on that assumption? What are the consequences if the assumption of small reserves proves to be wrong, and planning is based on that assumption?

[1] Strictly speaking, energy is not “consumed”, but rather is converted into different forms. When most people speak of "consuming" energy, the process they are describing is the conversion of energy to useful work or to energy stored in the form of (new) chemical bonds. During the conversion process, some of the available useful energy is transformed into radiant energy (light) and thermal energy (heat).

[2] Energy Information Administration, Office of Integrated Analysis and Forecasting, International Energy Outlook 2004, rep. no. DOE/EIA-0484(2004), U.S. Department of Energy, Washington, D.C. (April 2004).

[3] M.King Hubbert, "The world's evolving energy system", Am. J. Phys. 49 (11), 1007-1029 (1982). See Figure 5 on U.S. coal production.