Operating instructions
Table
2:
Data on Reserves, Consumption & Growth
of
2 Resources
C = C +
C*G
Increase
Consumption
7%
8%
7%
Growth
Now experiment with the input data.
Suppose the estimate
of
the reserve was
half as large as it really is. How does this
change the lifetime of the resource?
Does doubling the reserve double the
lifetime? Calculate the lifetime with a 0
per cent growth rate; a
10
per cent
growth rate. Get
data
on natural .gas,
copper,
or
other
non-renewable
resources and run the program. What
are the actual conditions under which
coal will last for centuries?
the corresponding BASIC program is
given
here.
There
is
only
one
approximation in the calculation. I
assumed
that
the consumption changes
abruptly at the end
of
a year, whereas
it
actually
changes more
or
less con-
tinuously throughout the year, much like
interest compounded daily. The approxi-
mation has
little
effect on the results.
The error is usually less than a year
or
two.
Next we need some
data
to
put into
the computer. This can
be
a
bit
tricky
because
companies
that
sell
the
resource
tend
to
overestimate the
reserves, while conservationists are pro-
bably biased in the other direction. The
truth
is
most
likely somewhere in the
middle. My
data
(and the inspiration for
this project) came from
an
article by Pro-
fessor
Albert
A.
Bartlett
in
the
September 1978 issue
of
the American
Journal
of
Physics. The data, which I
have taken the liberty
to
round
off
to
one
significant
digit, appears in Table
1.
Other references you might want
to
check are:
Dr.
M.
King Hubbert, A
National Fuels and Energy Policy Study,
Serial
93-40
(92-75)
Part
I,
U.S.
GPO,
Washington, D.C., 1973,
$2.35;
and
Dr.
M.
King Hubbert, "Energy Resources
of
the
Earth"
in
Scientific
American,
September 1971.
Almost
any computer should take the
simple BASIC program given here. Mine
ran on my
Microsoft
BASIC
for
the
KIM-1. Since almost every step is il-
lustrated in the flowchart, no further
ex-
planation
of
the program is necessary.
Load it and type in the
data
as they are
requested. When the
last
item
is
entered,
hit
RETURN and
wait
for
the
answer.
0.7 billion tons per yr.
6 billion barrels per yr.
20
billion barrels per yr.
Current Consumption Rate
Reserves
500
billion tons
100billion barrels
2000 billion barrels
R = R - C
Subtract
Consumption
from
Reserve
U.S.
Coal
U.S.
Oil
World Oil
Resource
Figure
1:
Flowchart to calaulate
the Lifetime
of
a Non-Renewable
Resource