Resource consumption
Rates of growth
Linear, exponential, geometric
Some resources are so abundant we don’t think about
exhaustion
Al, Ca, Cl, H, Fe, Mg, N, O, K, Si, Na, S
We should be careful about alarms.
In 1930, it was stated that our resources of copper will last 30
more years.
In 2008 is was stated that our resources of copper will last 30
years.
Annual world production
(tons/yr)
Use of materials by class (tons)
Sources of Energy
Sun
wind
wave
hydro
solar thermal
photovoltaic
Moon
Tidal
Nuclear decay
Energy use by source
(ExoJoules/yr)
Global energy consumption by
source
Global energy consumption by
use
Chemical
Types of Energy
fossil fuels, batteries, refined materials
Radiation
RF, microwave, infrared, optical, X-ray, gamma...
Thermal
high grade and low grade heat
Electrical and Magnetic
static and oscillating fields
Mechanical
potential and kinetic energy
Conversion
Energy can be converted from one form to another.
The efficiency, , tells us how well we convert (and
how much is lost)
Losses
Energy conversion usually has low grade heat as a
by-product, which is lost.
Exception is electrical to thermal, which has 100%
efficiency
Refining of metals, for example, involves conversion
of thermal or electrical energy to chemical energy.
Theoretically that energy could be recovered by
allowing the metal to oxidize again. But the effiency is
too low to be useful.
Conversion Efficiencies
There are limits to the conversion efficiencies.
Consider thermal to mechanical.
Carnot taught us that
where Tin is the temperature entering the heat engine
and Tout is the exit temp.
Carnot Efficiency with 150 C
output
Approximate efficiency factors
Conversion path
Efficiency
kg CO2/MJ
Fossil fuel to thermal (enclosed)
100
0.07
Fossil fuel to thermal (vented)
65-75
0.1
Fossil Fuel to electric
33-39
0.2
Fossil fuel to mechanical (steam
turbine)
28-42
0.17
Fossil fuel to mechanical (gas turbine)
46-50
0.15
Electric to thermal
100
0.2
Electric to mechanical (elec motors)
85-93
0.23
Electric to chemical (battery)
80-90
0.24
Electric to EM radiation (incand lamp)
15-20
1.17
Electric to EM radiation (LED)
80-85
0.23
Light to electric (PV)
10-20
0
Water
Water and materials
Growth of natural materials (some irrigated, some not)
Cooling cycles (with evaporative loss)
Dust suppression
Washing
Water to produce energy
Energy source
Water used (l/MJ)
Grid electricity
24
Industrial electricity
11
Energy direct from coal
0.35
Energy direct from oil
0.3
Reserves
a mineral Reserve, R, is that part of a known deposit
that can be extracted legally and economically at the
time it is determined.
Reserves are an economic construct, which change
depending on economics, technology and
legislation
The Resource Base is the real total. This includes
things we don’t know how to extract and estimates
unknown deposits.
Reserves vs. Resource Base
Rich already
exploited
Reserves
Improved
mining
tech
Increased
prospecting
Resource
Base
Lean
Certain
Geologic Certainty
Uncertain
Reserve movement
Commodity price (increased prices, increases
reserve)
Improved technology (increase reserve)
Production costs (increased costs, reduce reserve)
Legislation (can go either way)
Depletion (if production exceeds discovery, reduces
reserve)
Time to Exhaustion
Balance between supply and demand
Suppose the reserve is R, measured in total tons of
material
Let P be the production rate measured in tons per
year.
The the static index of exhaustion, tex,s will be
tex,s = R/P
Dynamic Index
The static index of exhaustion assumes there is no
growth.
Production rate can increase, for example.
If r is the rate of production increase per year, then
the dynamic exhaustion is
Copper: dynamic and static
indices
Market Efficiency
We are assuming an efficient market - the supply and
demand are in balance
If demand increases, then technology/economics
offset.
What happens if the market forces don’t work?
Market Breakdowns
Supply chain concentration
depend on a few countries/regions... if there are
problems...
Cartel Action
Stock piling
Substitutions
Recycling
Real criticality issues
The criticality of a resource is actually more
complicated.
The resource base is finite (although partly unknown).
The reserves increase for a while and then decrease
when prospecting is saturated.
The exploitation (production) begins to consume the
reserve, reducing it.
At some point, the rate of production exceeds the rate
of discovery. Then prices rise, and criticality is
pending.
Rate (tons/year)
Price
Production rate
Rate of discovery
Time
Indicators of criticality
Rate of growth of discovery falls below rate of growth
of production
Production rate starts to decline
Minimum economic ore grade falls
Prices start to rise
Real curves are not smooth...
Production and discovery
Reserves
Exercise
Consider the following data about a resource (next
slide).
Examine the trends (graph price, production and
reserves vs time). What conclusions can you reach?
Calculate the static index of exhaustion. What does
the result suggest about the reserves?
Resource data for exercise
Year
Price ($/kg)
World production (Mtons/year)
1995
2.93
9.8
310
1996
2.25
10.7
310
1997
2.27
11.3
320
1998
1.65
12.2
340
1999
1.56
12.6
340
2000
1.81
13.2
340
2001
1.67
13.7
340
2002
1.59
13.4
440
2003
1.78
13.9
470
2004
2.86
14.6
470
Reserves (M-tons)