Recycling Solutions - Thanatia: The Destiny of the Earth's Mineral Resources - page 435

velocities. It shows that although the proportion of recycled aluminium has in-
creased since the 1950s, secondary aluminium amounts to only 38% of the total
available on the market today as global demand for aluminium has grown concur-
rently.

100

100%

90% Primary Metal (%)

90

80% 80

70% 70

60% 60

50% 50

Total Metal Production

40% 40

30% 30

Recycled Metal (%)

20%

20

10%
0%

10
0

1950 1960 1970 1980 1990

2000 2010 2020

Fig. 14.3 Historic evolution of recycled aluminium and its primary production. Adapted from
Gerber (2007)

Based on Fig. 14.3, the reader is asked to suppose that in the period 1950-2020,
demand (denoted D) for aluminium grew annually by 2%, whilst the secondary
production (denoted R) grew by 0.25%. If one then goes on to understand that
this velocity will continue into the future, a simple calculation using an exponential
analysis indicates that some 250 years would be needed to obtain 98% e ciency
recovery rates 3 . Demand on the other hand would double close to around every 40
years 4 . If there were not any form of recycling at all, extraction (denoted M) would
double every 35 years (just five years earlier than if recycling exists). Furthermore,
upon reaching the ceiling of 98% recycling e ciency, should demand still continue to
grow at a 2% annual rate, extraction will still, despite all recycling attempts, double
every 35 years. Extraction of aluminium as a function of demand and recycling rates
is mathematically expressed in Eq. (14.1).

D(0) e (0:02t)
1 + R(0) (1 + 0:0025t)

M(t) = (14.1)

3 Recycling rates grow lineally with time and thus if today aluminium recycling rates are at 35%,
98% will be attained in: (98-35)/0.25=253 years.
4 Sagar and Frosch (1997) studied an exceptional case of recycling in New England, where over 95%
of the metal remains in the scrap recycling system. This is a considerable effort that leaves only
5% metal loss. However, this figure also means that, even when maintaining the same conditions,
within 15 years, all that is currently extracted will be dispersed.