**2.3 Fossil fuel reserves versus depletion time**

Most researchers estimate reserve depletion time by assuming constant production rates. For example, WEO 2006 estimated a ratio for oil of between 39 and 43 years, 164 year for coal and 64 years for gas. *Lior* (*2008*) assumed constant fossil fuel production rates and then estimated the ratio of production to reserves to be approximately 40, 60 and 150 for oil, gas and coal, respectively. As can be seen, none of the research modified the rate of production or consumption of fossil fuel to calculate the ratio of consumption to reserves. Consequently, the new model added this assumption and adjusted new formula to calculate fossil fuel reserve depletion time.


[*Source*: EIA and BP, and computed]

Table 2. Fossil fuel reserves depletion times

Table 2 illustrates the time that fossil fuels will be depleted using the Klass model and new model. As can be seen in this table, the Klass model for oil, coal and gas depletion times is calculated to be about 34, 106 and 36 years, respectively, compared to 35, 107 and 37 in the new model. Ultimately, the reserve of coal using either approach still has a longer

Fig. 3. Trends of world natural gas proven reserves and gas consumption from 1980 to 2007.

Most researchers estimate reserve depletion time by assuming constant production rates. For example, WEO 2006 estimated a ratio for oil of between 39 and 43 years, 164 year for coal and 64 years for gas. *Lior* (*2008*) assumed constant fossil fuel production rates and then estimated the ratio of production to reserves to be approximately 40, 60 and 150 for oil, gas and coal, respectively. As can be seen, none of the research modified the rate of production or consumption of fossil fuel to calculate the ratio of consumption to reserves. Consequently, the new model added this assumption and adjusted new formula to calculate

**Model Ratio of consumption to reserves Klass model New model** 

Oil Coal Gas Oil Coal Gas Oil Coal Gas

Year 40 200 70 34 106 36 35 107 37

Table 2 illustrates the time that fossil fuels will be depleted using the Klass model and new model. As can be seen in this table, the Klass model for oil, coal and gas depletion times is calculated to be about 34, 106 and 36 years, respectively, compared to 35, 107 and 37 in the new model. Ultimately, the reserve of coal using either approach still has a longer

[*Source*: EIA and BP]

fossil fuel reserve depletion time.

[*Source*: EIA and BP, and computed]

Table 2. Fossil fuel reserves depletion times

**2.3 Fossil fuel reserves versus depletion time** 

availability than oil and gas. This means that the coal reserves will be available until at least 2112 at this rate, and it will be the single fossil fuel in the world as indicated in Table 2. Fossil fuel reserves depletion times after 2042.

The second method tries to calculate the time that fossil fuels will be depleted by computing ratio of consumption to reserves. Thus, the average ratios of world consumption to reserves for oil, coal and gas can be computed from Fig. 1, Fig. 2 and Fig. 3.The graphs Fig.4, shows the trend of ratio of world consumption to reserves for oil, coal and gas from 1980 to 2006.

Fig. 4. The ratios of world consumption to reserves for oil, coal and gas from 1980 to 2006.

As can be seen in this figure these ratios for oil and gas were constant, around 40 and 60 years, respectively. This means that during the last 26 years, the reserves of oil and gas have not shown any decreasing trend during the last couple of decades and predictions that they were about to run out are not substantiated for the last 26 years (1980 to 2007) as seen from Fig. *1 and Fig. 3*. This means that if the world continues to consume oil, coal and gas at 2006 rates, their reserves will last a further 40, 200 and 70 years, respectively.
