Energy

Levels of primary energy sources are the reserves in the ground. Flows are production. The most important part of primary energy sources are the carbon based fossil energy sources. Oil, coal, and gas stood for 79.6% of primary energy production during 2002 (in million tonnes of oil equivalent (mtoe)) (34.9+23.5+21.2).

Levels (reserves) (EIA oil, gas, coal estimates, EIA oil, gas estimates)

Oil: 1,050,691 to 1,277,702 billion barrels (167 to 203 km³) 2003-2005 Gas: 6,040,208 - 6,805,830 billion cubic feet (171,040 to 192,720 km³) 6,805.830*0.182= 1,239 BBOE 2003-2005 Coal: 1,081,279 million short tons (1,081,279*0.907186*4.879= 4,786 BBOE) (2004) Flows (daily production) during 2002 (7.9 is a ratio to convert tonnes of oil equivalent to barrels of oil equivalent)

Oil: (10,230*0.349)*7.9/365= 77 MBD Gas: (10,230*0.212)*7.9/365= 47 MBOED Coal: (10,230*0.235)*7.9/365= 52 MBOED Years of production left in the ground with the most optimistic reserve estimates (Oil & Gas Journal, World Oil)[citation needed]

Oil: 1,277,702/77/365= 45 years Gas: 1,239,000/47/365= 72 years Coal: 4,786,000/52/365= 252 years Note that this calculation assumes that the product could be produced at a constant level for that number of years and that all of the reserves could be recovered. In reality, consumption of all three resources has been increasing.