Environmental Engineering Reference
In-Depth Information
Table 15.1
World reserves and production of several metals that may become limited in the next few
decades.
Confirmed estimated
world reserves (thousand
metric tons)
Production in 2010
(thousand metric tons)
Depletion time according to
current estimated reserves
(years)
Lead
a
80,000
4,100
20
Silver
510,000
22,200
23
Copper
630,000
16,200
39
Zinc
b
250,000
12,000
21
Tin
5,200,000
261,000
20
Gold
51,000
2,500
20
a
New reserves of lead has been recently discovered associated with zinc, silver, and copper deposits.
b
Identified new zinc deposits increase the potential availability to 1.9 billion tons.
Data from US Geological Survey, 2011.
Almost exclusively, polymers used for plastics come from oil and natural gas. In the case
of oil-based plastics, feedstocks are a derivative of the distillation process to produce gasoline.
So, as far as oil is available to produce gasoline, feedstocks are going to be accessible to pro-
duce plastics. If the concept of the biorefinery proves to be successful, plastics could possibly
be obtained from biomass in the future.
The environment
The environment is the life support system. Ultimately, natural ecosystems provide services to
replace the resources consumed and to process waste streams. Some of the services provided
by nature include carbon storage, production of oxygen, water cycling, water filtration, flood
control, coastal protection, nutrients cycling, pollination, animal habitats, seed dispersion,
pest and disease control, and climate control. Therefore, preservation of natural ecosystems is
more than vital for long-term sustainability.
THE PEAKS IN THE PATHWAY OF SUSTAINABILITY
Peak oil
Peak oil is the point at which the maximum rate of oil production is reached and after that it
starts to decline. Reaching peak oil is not a matter of if but a matter of when, and its prediction
is as politicized as climate change. On one side, the pessimistic camp sustains that the peak
has been reached and from here production is going to start declining. The other side somehow
agrees that oil is a limited resource but believes that there are undiscovered reserves and that
human ingenuity will solve the problem with new exploration techniques, advanced drilling
procedures, and exploitation of unconventional sources.
The pessimistic view of peak oil is supported by the work of King Hubbert who in 1956
predicted that US oil production would peak around 1970 and then start declining. As is
shown in Figure 15.3, oil peaked in 1971 and after that the United States has relied heavily on
imports. And with exception of the Middle East, most countries of the rest of the world have
already passed the peak (Government Accountability Office [GAO], 2007).
Following Hubbert's models, other scientists refined his methodology and made predic-
tions about the global oil peak and decline. Most studies indicate that oil will peak sometime
