1. Session 7 – Sustainability and
Fossil Fuels

2. Definitions of Sustainability
One definition:
• For renewables: Usage rate < generation rate
• For non-renewables: Usage rate < sustainable use rate of
substituted renewable
• For a pollutant: Emission rate < rate of recycling,
absorption, or neutralization
The ideal requires complete reliance on renewables.
Another definition related to GHGs:
• Sustainability means meeting energy needs w/o adverse
warming

3. Sustainability – Who Cares?
• Life is day-to-day in many countries
• However, all countries face a global
market for primary fuels – price is a force
• Pie charts, p 264: China, Middle
East/Africa will outpace US energy use by
2095 – will all three adopt the ideal?
• If sustainability erodes economies, can we
maintain or improve human condition?

4. A Conundrum
• Human Development Index (HDI) of
United Nations: Humans need > 4 MWh
annually of electricity for well being
• Yet, the UN IPCC predicts temp rises of
1.4 to 5.8 °C by 2100
• Do we meet basic human needs and
suffer climate change consequences, or
leave needs unmet with a more stable
environment?

5. Assessing Technology for
Sustainability
• Engineering may yield an answer that is not
mutually exclusive!
• Comparing conversion systems is difficult
• UN uses three general indicators to measure
sustainability:
• Environmental
• Economic
• Social
• Let’s compare wind and nuclear using these
indicators

6. Cornerstones of Sustainable
Energy Policy
Customers
(Regulatory or
market-based?)
Technology
Capital
(Technically feasible
at required scale?
Public or private
development?)
(Who will invest,
what risk/return
profile?)

7. Fossil Energy
• Recall: About 80% of US energy is fossil; 70%
of US electricity is fossil based
• Recall: Fossil = coal, natural gas, petroleum
• P. 296: “A fossil fuel is a substance that
releases energy by a chemical reaction.”
– This is a necessary but not sufficient definition
– Also needs to be organic, have covalently bonded
Carbon, and be produced over geological time
periods
– Consider how biofuels meet parts of these definitions

8. Fossil Energy Reserves
Example from Sample Problem 7.1
They appear huge . . .
for Coal, 290,000 Quads (roughly)
World annual energy use in 1995 was 325 Q
If rate stayed constant, and if coal used
exclusively,
Reserves would last for 846 years

9. Fossil Energy Reserves
Example from Sample Problem 7.1
However, with 2% annual growth in
consumption, reserves shrink to 144
years.
Are reserves increasing each year?
Are countries and reporting entities trusted
sources for national reserves?

10. Fossil Energy Reserves
North Dakota Lignite Reserves
•351 billion tons of known lignite reserves
•25 billion tons that are economically recoverable – good for 800 years
•32 million tons produced annually – steady production for a decade or more
•At 7000 Btus/pound, North Dakota reserves contain 4.8 E 18 Btus
or 4800 Quads
Enough to power the world for over 10 years.
Source: North Dakota Geological Survey; Lignite Energy Council