Energy: Fossil Fuels
Part II: Natural Gas and Coal
Natural Gas
Natural gas is produced by decomposition of
deeply buried organic matter from plants & animals.
• natural gas is a mixture of 50–90% methane (CH4),
with smaller amounts of ethane (C2H6), propane
(C3H8), & butane (C4H10), and the toxic gas hydrogen
sulfide (H2S);
• when a natural gas field is tapped,
propane & butane gases are removed
as _____________________________
• natural gas is typically transported in
pipelines from oil fields to users;
• since many oil wells are isolated, much of the natural
gas is either _______ or pumped back into the ground
because it is not economically feasible to transport it.
Natural Gas
Carbon dioxide emissions per unit energy
produced is much lower for natural gas, as
compared with other fossil fuels.
Types of Natural Gas
Conventional natural gas:
• trapped above oil deposits and is
usually fairly easy to extract.
Unconventional natural gas:
•
______: gas locked in impermeable
rock (usually sandstone)*
•
______: gas locked in shale beds
(where gas originally formed)*
•
___________________methane
•
Methane ___________ (frozen on
ocean floor)
*Requires Fracking
Natural Gas Reserves
Natural Gas
Reserves and
Demand
Natural Gas Consumption
Natural Gas Extraction: Fracking
_________________: aka Fracking
• rock (often shale) is fractured by
a pressurized liquid made of
water, sand, and chemicals.
• When the hydraulic pressure is
removed from the well, small
grains of proppants (either sand
or aluminum oxide) hold the
fractures open.
Natural Gas Extraction: Fracking
Environmental Concerns:
• The frack fluid mostly contains water (89%), with another 9.3%
of the fluid being sand. The remaining chemicals constitute
1.7%, of the mixture.
• New fractures formed may allow migration of gas, chemicals, or
other materials into drinking water supplies (either below the
surface or in lakes/streams)
• Radioactive tracer elements and ___________ chemicals used
in fracking fluids have also been found in ______________.
Natural Gas Extraction: Fracking
Environmental Concerns: Several studies have found fracking
fluids in the drinking water of nearby towns and residents.
Natural Gas Extraction: Fracking
Environmental Concerns:
• Fracking might cause
earthquakes in the area
• EPA has not regulated the
process, and Obama supports
the process
•https://www.youtube.com/watch?v=LAxsTJd7VCA
•https://www.youtube.com/watch?v=4LBjSXWQRV8
Transporting Natural Gas
• Pipelines extend
for hundreds of
miles, which can
be hazardous
• Pipelines may also
leak
• Natural Gas is also
transported in
ships and trucks
Puget Sound
Energy
• Natural Gas Supply:
Western US = 43%
BC = 35%
Alberta = 22%
• Natural Gas Demand
Residential = 49%
Commercial = 26%
Industrial & Transportation = 25%
Natural Gas Lines: Aging Infrastructure
• Many natural gas lines
to individual homes or
businesses are old and
starting to fail.
• Failure of a gas line
can cause catastrophic
explosions
• A smell is added to the
gas, so that people will
recognize when there’s
gas present.
Natural Gas Explosion: February 7th, 2010
TRADE-OFFS
Conventional Natural Gas
Advantages
Disadvantages
Ample supplies
High net energy yield
Low cost
Less air pollution
than other fossil fuels
Lower CO2 emissions
than other fossil fuels
Easily transported by
pipeline
Nonrenewable
resource
Releases CO2 when
burned
Gas turbine Government subsidies
Environmental costs not
included in market price
Methane (a greenhouse
gas) can leak from
pipelines
Low land use
Difficult to transfer from
one country to another
Good fuel for fuel cells,
gas turbines, and motor
vehicles
Can be shipped across
ocean only as highly
explosive LNG
Methane Hydrates
• Methane hydrates are
methane molecules (CH4)
encased in an ______lattice
• Stable only at ______
pressures and
_____temperatures
• Boils off at STP, and is
extremely _______________
• Formed as a by-product from
microbes living in ocean
floor sediments
Methane Hydrates
• Volume of methane hydrate
is massive, but technology
does not currently exist to
safely or ______________
extract it
Methane Hydrate Deposits
•Fig. S10-7, p. S63
Methane Hydrates
• Catastrophic releases of methane
hydrate have been proposed to have
caused major _________ shifts (due to
massive CO2 release), and possibly
mass extinctions in the past
• In order to mine it,
safe methods need
to be developed
• Various countries
(including US) are
investigating this
potential resource
The Future?
Coal
Natural gas
•Fig. S10-5, p. S61
Coal
Coal is a fossil fuel,
produced from the
buried remains of
___________ plants
that died during the
Carboniferous period
(geologic era ending
286 million years ago).
Fig.15–13
Stages in the
formation of coal
over millions of
years. Note the
three types of coal.
Coal
Coal is mostly carbon, with
smaller amounts of water,
_________ & trace amounts of
radioactive materials and
elements such as mercury. It is
typically extracted by strip mining
or underground coal mining.
Coal Sources & Uses
About 66% of the world's proven coal reserves and
85% of the estimated undiscovered deposits are in the
United States, the former Soviet Union, and China.
• Coal provides about ______ of the world's commercial
electricity (22% in U.S.);
• used to generate 64% of world's electricity
(57% in U.S.);
• used to make _______ of world's steel;
• China gets _____ of energy from coal, largest
user;
• U.S. second largest user
Coal Sources
Locations of the
major coal fields in
the United States &
Canada.
Fig.15–14
© Brooks/Cole Publishing Company / ITP
Coal: Environmental Concerns
• Mountaintop Removal: The
process of removing the
tops of mountains, mostly in
the _______________s, to
remove the coal seams
beneath them.
• Effects:
• _____for coal miners and
requires fewer men
• Destroys the tops of mountains
• Overburden is pushed into
valleys
• Sediment-laden water is no
longer usable for drinking or fish
• Creates _________ downstream
Coal: Environmental Concerns
•https://www.youtube.com/watch?v=p5RcbPZXUZo
•https://www.youtube.com/watch?v=RPixjCneseE
Mountaintop Removal Mining
Air Pollution from Coal: Acid Rain and Soot
Coal contains sulfur and nitrogen impurities. Sulfur dioxide (SO2)
and nitrogen oxides (NOx) are emitted from coal burning. These
molecules react in the atmosphere to form sulfuric and nitric
_________.
____ of all SO2 and ____of all NOx comes from electricity
generated by fossil fuels (especially coal).
East coast uses a greater percentage of
coal and has more acid rain.
Mercury Emissions from Coal
Coal is naturally contaminated with
mercury, which is released when it
is burned.
Coal-burning power plants and
industrial boilers are the greatest
contributor to mercury pollution.
Waste heat
Coal bunker Turbine
Cooling tower
transfers waste heat
to atmosphere
Generator
Cooling loop
Stack
Pulverizing
mill
Boiler
Condenser
Filter
Toxic ash disposal
Air Pollution from Coal: Soot
Carbon ________ both contributes to global
warming and is a harmful air pollutant (fine
particulate matter.)
Methods of Reducing Air Pollution:
Precipitators
______________
Higher _________ coal
Videos on Coal:
http://www.cbsnews.com/video/watch/?id=4969902n
http://www.cbsnews.com/video/watch/?id=6369590n
http://www.cbsnews.com/video/watch/?id=4969906n
http://www.cbsnews.com/video/watch/?id=5356259n
Scrubbers can reduce Sulfur Dioxide Emissions
Conversion of solid coal to
-Synthetic natural gas (SNG) by coal gasification
- Methanol or synthetic gasoline by coal liquefaction
Advantages
Synthetic fuels
Large potential
supply
Disadvantages
Low to moderate net
energy yield
Higher cost than coal
Vehicle fuel
Requires mining 50%
more coal
Environmental costs not
included in market price
Moderate cost
High environmental impact
Large government
subsidies
Lower air pollution than
coal when burned
High water use
Higher CO2 emissions
than coal
Clean Coal
“Coal is an abundant resource in the world…It is imperative
that we figure out a way to use coal as cleanly as possible.”
-- Dr. Steven Chu, Secretary of Energy at his Senate
Confirmation Hearing, January 13th, 2009
Clean coal technologies aim to sharply reduce air
emissions and other pollutants from coal plants
• Early clean coal efforts in the late 1980’s and early
1990’s focused on reducing acid rain through reduction
of sulfur _____________
• New concerns include impacts
of trace amounts of ________
and the effects of CO2 on
global climate
Clean Coal
Clean Coal Power Initiative (CCPI):
• Provides government co-financing for new coal
technologies that can help utilities cut sulfur, nitrogen, and
mercury pollutants from power plants, as well as improve
efficiency
• 2003: Eight projects selected. Two are currently in the
operational phase; one has been completed; and the other 5
have been discontinued
• 2004: Four projects selected. One is in the operational
phase; two are under development; one has been withdrawn.
• A third solicitation for projects is underway and is focused
on developing projects that utilize carbon sequestration
technologies and/or beneficial reuse of CO2
Carbon Sequestration
Involves injection of CO2 into geologic formations such as oil
and gas reservoirs, unmineable coal seams, and deep saline
reservoirs
• Injection into ________________deposits can enhance
recovery of oil and natural gas
• May be able to store CO2 produced from coal plants for long
periods of time
• Norwegian company,
Statoil, is injecting 1 million
tons of recovered CO2 into
the Utsira Sand Saline
Formation. This is the
equivalent to the output of
a 150-megawatt coal-fired
plant
Sequestering Carbon
Oil rig
Tanker delivers
CO2 from plant Coal power
to rig
plant
CO2 is pumped
down from rig for
disposal in deep
ocean or under
seafloor sediments
Abandoned
oil field
Tree plantation
Switchgrass
Crop field
CO2 is
pumped
underground
Spent oil or
natural gas
reservoir
Spent coal
bed cavern
Deep, saltwater-filled cavern
= CO2 pumping
= CO2 deposit
• Coal puts more CO2
into the atmosphere
than any other fossil
fuel
• More than 60% of
coal mined in US
comes from _______
mines
• Coal Sequestration
is a new technology
that is a long way from
being implemented on
a large scale in the US
and is not currently
economically viable
without large
government subsidies
Can Coal Be Clean?
Problems with carbon
capture and storage
– Power plants using CCS
• Would be more
___________ to build
– Unproven technology
– Stored CO2 would have
to
remain sealed forever:
no __________
– Large inputs of __________
to work
• Increasing CO2 emissions, negating some of “carbon
offset”
– Promotes the continued use of coal (world’s dirtiest fuel)
Pros:
Coal Pros & Cons
• most abundant fossil fuel;
• U.S. has major reserves, will last 300 years at current
consumption rates;
• high net energy yield;
Cons:
• dirtiest fossil fuel, in terms of air pollution & carbon dioxide
released;
• major environmental degradation
that result from extraction,
processing, transport, & use;
• burning coal is major threat to
human health –– estimated to kill
or cause chronic respiratory disease for large numbers of people.
• Coal Mining is a hazardous profession: more than 104,000
© Brooks/Cole Publishing Company / ITP
miners have died in America since 1900
TRADE-OFFS
Coal
Advantages
Ample supplies (225–900
years)
High net energy yield
Low cost
Well-developed
technology
Air pollution can be
reduced with improved
technology
Disadvantages
Severe land
disturbance, air
pollution, and water
pollution
Severe threat to human
health when burned
Environmental costs
not included in
market price
Large government
subsidies
High CO2 emissions
when produced and
burned
Radioactive particle and
toxic mercury emissions
Coal-fired
electricity
286%
Synthetic oil and
gas produced from
coal
150%
Coal
100%
Oil
sand
92%
Oil
86%
Natural gas
Nuclear power
fuel cycle
58%
CO2 Emissions per
unit of Electrical
Energy
17%
Geothermal 10%
Fig. 15-14, p. 384
Things You Can Do…
Cut down waste
where you can