Environmental Engineering Reference
In-Depth Information
TABLE 2.4
Estimated Resources or Reserves, 2007
Resource
Amount
U.S. crude oil
42 * 10
9
barrels
U.S. oil
80 * 10
9
barrels
U.S. natural gas
630 * 10
12
ft
3
U.S. coal
243 * 10
9
metric tons
U.S. uranium oxide
1 * 10
5
metric tons @ $66/kg
www.eia.doe.gov/cneaf/nuclear/page/reserves/ures.html
4 * 10
5
metric tons @ $110/kg
World crude oil (conventional)
1.1 * 10
12
barrels
World oil; includes heavy, sands, shale, deep sea, polar oil
2.1 * 10
12
barrels
World natural gas
6200 * 10
12
ft
3
World coal
907 * 10
9
metric tons
World uranium oxide
2 * 10
6
metric tons @ $80/kg
www.euronuclear.org/info/encyclopedia/u/uranium-reserves.htm
5 * 10
6
metric tons @ $130/kg
2.9 LIFETIME OF A FINITE RESOURCE
If the magnitude of the resource is known, or can be estimated, then the end time,
T
E
, when that
resource is used up, can be calculated for different growth rates. The size of resource,
S
, is put in
Equation 2.9, and the resulting equation is solved for
T
E
:
r
k
e
kT
E
S
0
(
1
)
¤
¦
¥
³
µ
´
1
S
r
T
E
ln
k
1
(2.10)
k
0
If the demand is small enough or is reduced exponentially or reduced at the depletion rate, a
resource can essentially last a very long time. However, with increased growth,
T
E
can be cal-
culated for different resources (Table 2.4), and the time before the resource is used up is gener-
ally short. Remember, these are only estimates of resources, and other estimates will be higher
or lower.
EXAMPLE 2.6
How long will conventional world oil last if consumption grows at 3%/year?
r
0
30 * 10
9
barrels/year,
S
1,100 * 10
9
barrels,
k
0.03
Place values in Equation 2.10:
¤
¦
¥
³
µ
´
1
003
003
1100
*
10
9
T
E
ln
.
1
33 ln(2.1) 33 * 0.74 24 years
.
30
*
10
9
If you do not use the equation, a spreadsheet is very useful for calculations, as you can play
with different scenarios of growth and size of the resource.
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