New trends in physics teaching, v.4; The ... - unesdoc - Unesco

New Trends in Physics Teaching IV
When consumption grows 7 per cent each year the consumption in any decade is approximately
equal to the sum of all previous consumption, as can be seen by the areas representing
consumption in successive decades. The rectangle ABDC represents all known
that has been used in the past; the rectangle CDFE represents the new d
made if we wish the 7per cent growth to continue for the decade from the year
From these calculations, we can draw a general conclusion of great impmtzmce. When we are
dealing with exponential growth, we do not need to have an accurate 0te of the size of a
resource in order to make a reliable estimate of how long the resource
TABLE 5.
Col I
Zero
1%
2%
3%
4%
5%
6%
7%
8%
9%
1 WO
Life expectancy in years of various estimates of world oil reserves for different rates growth of annual
production. Units are lo9 barrels. This table was prepared by using Eq. (6) with r,
= 16.7 X lo9
barrels/year. Column 1 is the percentage annual growth rate of production. Column 2 is the EET of
the resource calculated using R = 1691 as the estimate of the amount of the remaining oil. Column 3
is the EET calculated using R = 169 1 + 190 = 1881 representing crude oil plus shale. Column 4 is the
EET calculated using R = 169 1 + 4( 190) = 245 1 which assumes that the amount of shale oil is four
times the amount which is known now.
Col 2 (year)
101
699
55.3
46.5
40.5
36.0
32.6
29.8
27.6
25.7
24.1
Col 3 (year)
113
75.4
59.0
49.2
42.6
37.8
34.1
312
28.8
26.8
25.1
Col 4 (yea)
I47
90.3
68.5
562
48.2
42.4
38.0
34.6
31.8
29.5
27.5
In a recent advertisement in papers and magazines in the United States a major American oil
company said: ‘Vast oil potential in the U.S. untapped and unavailable’. The advertisement
went on to note that ‘the United States may still have as much undiscovered and unproduced
oil as has been used in our entire history’. The optimistic tone of the advertisement (the oil
remaining is equal to all we have used) is negated by a simple understanding of what is meant
by the fact that we have already used one half of the recoverable oil that was ever in the ground
in the United States. The ‘oiltime’ is one minute before noon.
As the reader ponders the seriousness of the situation and asks ‘What will life be like without
petroleum?’ the thought arises of heating homes electrically or with solar power and of travelling
in electric cars. A far more fundamental problem becomes apparent when one recognizes that
modern agriculture is based on petroleum-powered machinery and on petroleum based fertilizers.
This is reflected in the definition ‘Modern agriculture is the use of land to convert petroleum to
food.’
NEWS ITEM (Exxon News [ 81 )‘United States agriculture is the most energy intensive in the
world. From farm to ultimate consumer all of its activities account for about 15% of total United
States energy consumption. Oil and gas combine to meet about 80% of agriculture’s energy needs.
The petroleum and agriculture industries have been partners in making United States agriculture
the most productive in the world. In 1850, the average American farmer could raise food for
himself and four others. Today, such a farmer could feed himself and 59 others. By the year
2000 he expects to feed himself and 95 others.’
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