Energy: Fossil Fuels Part II: Natural Gas and Coal

Transcription

1 Energy: Fossil Fuels Part II: Natural Gas and Coal

2 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 (CH 4 ), with smaller amounts of ethane (C 2 H 6 ), propane (C 3 H 8 ), & butane (C 4 H 10 ), and the toxic gas hydrogen sulfide (H 2 S); 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.

3 Natural Gas Carbon dioxide emissions per unit energy produced is much lower for natural gas, as compared with other fossil fuels.

4 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

5 Natural Gas Reserves

6 Natural Gas Reserves and Demand

7 Natural Gas Consumption

8 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.

9 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.

10 Natural Gas Extraction: Fracking Environmental Concerns: Several studies have found fracking fluids in the drinking water of nearby towns and residents.

11 Natural Gas Extraction: Fracking Environmental Concerns: Fracking might cause earthquakes in the area EPA has not regulated the process, and Obama supports the process

12 Natural Gas is also transported in ships and trucks Pipelines extend for hundreds of miles, which can be hazardous Pipelines may also leak Transporting Natural Gas

13 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.

14 TRADE-OFFS Conventional Natural Gas Advantages Disadvantages Ample supplies High net energy yield Low cost Less air pollution than other fossil fuels Lower CO 2 emissions than other fossil fuels Easily transported by pipeline Low land use Gas turbine Nonrenewable resource Releases CO 2 when burned Government subsidies Environmental costs not included in market price Methane (a greenhouse gas) can leak from pipelines 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

15 Methane Hydrates Methane hydrates are methane molecules (CH 4 ) 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

16 Methane Hydrates Volume of methane hydrate is massive, but technology does not currently exist to safely or extract it

17 Methane Hydrates Catastrophic releases of methane hydrate have been proposed to have caused major shifts (due to massive CO 2 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

18 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 Stages in the formation of coal over millions of years. Note the three types of coal.

19 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.

20 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

21 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

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23 Mountaintop Removal Mining

24 Air Pollution from Coal: Acid Rain and Soot Coal contains sulfur and nitrogen impurities. Sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) are emitted from coal burning. These molecules react in the atmosphere to form sulfuric and nitric. of all SO 2 and of all NO x comes from electricity generated by fossil fuels (especially coal). East coast uses a greater percentage of coal and has more acid rain.

25 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.

26 Waste heat Coal bunker Turbine Cooling tower transfers waste heat to atmosphere Generator Cooling loop Pulverizing mill Boiler Condenser Filter Stack Toxic ash disposal

27 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:

28 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 13 th, 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 CO 2 on global climate

29 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 CO 2

30 Carbon Sequestration Involves injection of CO 2 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 CO 2 produced from coal plants for long periods of time Norwegian company, Statoil, is injecting 1 million tons of recovered CO 2 into the Utsira Sand Saline Formation. This is the equivalent to the output of a 150-megawatt coal-fired plant

31 Sequestering Carbon Oil rig Tanker delivers CO 2 from plant to rig Coal power plant Tree plantation CO 2 is pumped down from rig for disposal in deep ocean or under seafloor sediments Abandoned oil field Switchgrass CO 2 is pumped underground Crop field Spent oil or natural gas reservoir Spent coal bed cavern Deep, saltwater-filled cavern = CO 2 pumping = CO 2 deposit

32 Coal puts more CO 2 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?

33 Problems with carbon capture and storage Power plants using CCS Would be more to build Unproven technology Stored CO 2 would have to remain sealed forever: no Large inputs of to work Increasing CO 2 emissions, negating some of carbon offset Promotes the continued use of coal (world s dirtiest fuel)

34 Pros: Coal Pros & Cons most fossil fuel; U.S. has major reserves, will last 300 years at current consumption rates; net energy yield; Cons: 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

35 TRADE-OFFS Coal Advantages Ample supplies ( 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 CO 2 emissions when produced and burned Radioactive particle and toxic mercury emissions

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37 Fig , p. 384 Coal-fired electricity Synthetic oil and gas produced from coal Coal 100% 150% 286% Oil sand 92% Oil 86% Natural gas 58% CO 2 Emissions per unit of Electrical Energy Nuclear power fuel cycle 17% Geothermal 10%

38 Cut down waste where you can Things You Can Do