Post on 14-Jan-2016
Energy: Fossil FuelsPart II: Natural Gas and Coal
Natural GasNatural 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 GasCarbon dioxide emissions per unit energy produced is much lower for natural gas, as compared with other fossil fuels.
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
Types of Natural Gas
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: FrackingEnvironmental 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: FrackingEnvironmental Concerns: Several studies have found fracking fluids in the drinking water of nearby towns and residents.
Natural Gas Extraction: FrackingEnvironmental 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 GasAdvantages DisadvantagesAmple supplies Nonrenewable
resourceHigh net energy yield
Releases CO2 when burnedLow cost
Gas turbine Government subsidiesLess air pollution than other fossil fuels Environmental costs not
included in market price
Lower CO2 emissions than other fossil fuels Methane (a greenhouse
gas) can leak from pipelinesEasily transported by
pipelineDifficult to transfer from one country to anotherLow land use
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
• Fig. S10-7, p. S63
Methane Hydrate Deposits
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?
• Fig. S10-5, p. S61
Coal
Natural gas
CoalCoal is a fossil fuel, produced from the buried remains of ___________ plants that died during the Carboniferous period (geologic era ending 286 million years ago).
Stages in the formation of coal over millions of years. Note the three types of coal.
Fig.15–13
CoalCoal 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 & UsesAbout 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
© Brooks/Cole Publishing Company / ITP
Locations of the major coal fields in the United States & Canada.
Fig.15–14
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 SootCoal 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 CoalCoal 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
GeneratorCooling loop
Stack
Pulverizing mill
Condenser Filter
Boiler
Toxic ash disposal
Air Pollution from Coal: SootCarbon ________ 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 liquefactionSynthetic fuelsAdvantages Disadvantages
Large potential supply
Low to moderate net energy yield
Higher cost than coal
Vehicle fuelRequires mining 50% more coal
Environmental costs not included in market price
Moderate cost High environmental impact
Large government subsidies
High water useLower air pollution than coal when burned
Higher CO2 emissions than coal
Clean Coal
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
“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 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
Clean Coal
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
Oil rigTanker delivers CO2 from plant to rig
Coal power plant
Tree plantation
CO2 is pumped down from rig for disposal in deep ocean or under seafloor sediments
Abandoned oil field
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
Sequestering Carbon
Can Coal Be Clean?• 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
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)
Coal Pros & Cons
© Brooks/Cole Publishing Company / ITP
Pros:• 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 miners have died in America since 1900
TRADE-OFFS
CoalAdvantages Disadvantages
Severe land disturbance, air pollution, and water pollution
Ample supplies (225–900 years)
High net energy yield
Environmental costs not included in market price
Low cost
Large government subsidies
Well-developed technology High CO2 emissions when
produced and burned
Air pollution can be reduced with improved technology
Severe threat to human health when burned
Radioactive particle and toxic mercury emissions
Fig. 15-14, p. 384
Coal-fired electricity
286%
Synthetic oil and gas produced from
coal
150%
Coal 100%
Oil sand
92%
Oil 86%
Natural gas 58%
Nuclear power fuel cycle
17%
Geothermal 10%
CO2 Emissions per unit of Electrical Energy
Things You Can Do…Cut down waste where you can