AP Environmental Science. Unit Seven

Transcription

1 AP Environmental Science Unit Seven

2 I. Fossil Fuels

3 Fossil Fuels

4 Overview of Fossil Fuels Energy Sources and Consumption Energy Policy Fossil Fuels Coal Oil and Natural Gas Synfuels ANWR

5 energy consumption and resources

6 Energy Sources and Consumption Energy sources used to be local Now they are worldwide Fossil fuels Nuclear energy Electricity Energy consumption is different between developing and developed nations 20% of world s population use 60% of the world s energy sources

7 Energy Sources and Consumption Energy density Amount of energy contained in a given volume or mass of an energy source Energy efficiency A measure of the fraction of energy used relative to the total energy available in a given source

8 Energy Sources and Consumption Per capita energy consumption of selected developed and developing countries

9 Energy Consumption in the US

10 energy policy

11 US Energy Policy Objective 1: Increase Energy Efficiency and Conservation Requires many unpopular decisions Examples Decrease speed limit to conserve fuel Eliminate government subsidies Objective 2: Secure Future Fossil Fuel Energy Supplies 2 oppositions: environmental and economic

12 US Energy Policy Objective 3: Develop Alternative Energy Sources Who should pay for this? Gas taxes? Objective 4: Meet the First Three Objectives Without Further Damage to the Environment

13 fossil fuels: coal, oil natural gas

14 Fossil Fuels Combustible deposits in the Earth s crust Composed of the remnants (fossils) of prehistoric organisms that existed millions of years ago Includes coal, oil (petroleum) and natural gas Non-renewable resource Fossil fuels are created too slowly to replace the reserves we use

15 How Are Fossil Fuels Formed? 300 million years ago Climate was mild Vast swamps covered much of the land Dead plant material decayed slowly in the swamp environment

16 How Are Fossil Fuels Formed Coal Heat, pressure and time turned the plant material into carbon-rich rock (coal) Oil (petroleum) Sediment deposited over microscopic plants Heat pressure and time turned them into hydrocarbons (oil) Natural Gas Formed the same way as oil, but at temperatures higher than 100 C

17 Coal Most, if not all, coal deposits have been identified Occurs in different grades - based on variations in heat and pressure during burial

18 Coal Worldwide coal deposits are widespread and extensive US has 25% of world s coal supplies Coal is North America s most abundant fossil fuel Known coal deposits could last 200 years At present rate of consumption

19 Coal

20 2 Types of Coal Mining Surface mining (right) Chosen if coal is within 30m of surface Subsurface mining Extraction of mineral and energy resources from deep underground deposits

21 Safety concerns of Mining Coal Significant human safety and health risks 20th century saw 90,000 deaths related to coal mining Accidents Cancer Black Lung Disease: inhalation of coal dust causes inflammation and fibrosis in lungs

22 Environmental Impacts of Mining Coal Surface Mining Control and Reclamation Act (1977) Requires filling (reclaiming) of surface mines after mining Reduces Acid Mine Drainage Requires permits and inspections of active coal mining sights Prohibits coal mining in sensitive areas

23 Mountain Top Removal

24 Environmental Impacts of Burning Coal Releases large quantities of CO 2 into atmosphere Greenhouse gas Releases other pollutants into atmosphere Sulfur oxides (mainly) Mercury Nitrogen oxides Can cause acid precipitation

25 Making Coal Cleaner Scrubbers (remove sulfur oxides) Fluidized Bed Combustion (below)

26 Oil and Natural Gas Oil and gas provide 60% of world s energy They provide 62% of US s energy

27 Petroleum Refining Numerous hydrocarbons present in crude oil (petroleum) are separated Based on boiling point Natural gas contains far fewer hydrocarbons than crude oil Methane, ethane, propane and butane

28 Oil and Natural Gas Exploration Oil and natural gas migrate upwards until they hit impermeable rock Usually located in structural traps

29 Oil Reserves Uneven distribution globally More than half is located in the Middle East Oil Wells usually extract 30-40% of oil in the resavoir

30 Natural Gas Reserves Uneven distribution globally More than half is located in Russia and Iran Natural is most efficient fuel with only 10% of energy content lost in shipping and handling

31 How long will Supplies Last? Difficult to determine and estimates vary Depends on: Locating more deposits Future extraction technologies Changes in global consumption rates Experts indicate there may be shortages in 21 st century

32 Environmental Impacts of Oil and Natural Gas Combustion Increase carbon dioxide and pollutant emissions Natural gas is far cleaner burning than oil Production Disturbance to land and habitat Transport Spills - especially in aquatic systems Ex: Alaskan Oil Spill (1989)

33 1989 Alaskan Oil Spill

34 1989 Alaskan Oil Spill Exxon Valdez hit a reef and spilled 260,000 barrels of crude oil into sound Largest oil spill in US history Led to Oil Pollution Act of 1990

35 ANWAR

36 Case in Point - Arctic National Wildlife Refuge (ANWR)

37 ANWAR Biologically rich and extremely fragile ecosystem located in Alaska Debated over last decades to open the area to exploration and drilling 14 million barrels have already been extracted from Prudhoe Bay but reached peak in 1985 and declined ever since At 50$ a barrel about 7 billion barrels could be profitably extracted Opposition feels that this is a short term and temp fix and

38 fossil fuels: synfuels

39 Synfuel and Other Fossil Fuel Resources Synfuel Synthesized fuel from coal and other naturally occurring sources Used in place of oil or natural gas Include: Tar sands Oil shales Gas hydrates Liquefied coal Coal gas (right)

40 II. Nuclear Energy

41 Nuclear Energy

42 Overview of Nuclear Energy Introduction to Nuclear Power Nuclear Fission Pros and Cons of Nuclear Energy Safety Issues at Power Plants Radioactive Waste Future of Nuclear Power

43 Introduction to Nuclear Energy

44 Introduction to Nuclear Energy Nuclear Energy - the energy released by nuclear fission or fusion Henri Becquerel Marie Curie (right) Ernest Rutherford

45 Introduction to Nuclear Energy Nuclear energy Energy released by nuclear fission or fusion Nuclear fission Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy Nuclear fusion Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

46 Atoms and Radioactivity Nucleus Comprised of protons (+) and neutrons (neutral) Electrons ( ) orbit around nucleus Neutral atoms Same # of protons and electrons

47 Atoms and Radioactivity Atomic mass Sum of the protons and neutrons in an atom Atomic number Number of protons per atom Each element has its own atomic number Isotope Atom where the number of neutrons is greater than the number of protons

48 Radioactive Isotope Unstable isotope Radioactive Decay Emission of energetic particles or rays from unstable atomic nuclei Example Uranium (U-235) decays over time to lead (Pb-207) Each isotope decays based on its own half-life

49 Radioactive Isotope Half-lives

50 Nuclear Fission

51 Nuclear Fission Nuclear Fuel Cycle processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes Uranium is extensively processed to clean and purify it

52 Nuclear Fission

53 How Electricity is Produced

54 How Electricity is Produced Fuel Rods closed tubes about 12 ft long that hold Uranium pellets each rod contains hundreds of pellets, each pellet contains equivalent energy of 1 ton of coal Fuel Assemblies hold fuel rods a typical nuclear reactor holds about fuel assemblies Reactor Core location of fission reactions

55 How Electricity is Produced Control Rods special metal alloy that absorbs neutrons Turbine uses steam to generate electricity Condenser cools steam and converts back to liquid

56 How Electricity is Produced PWR (pressurized water reactors) and BWR (boiling water reactors) both use Uranium 235 as their fuel 2/3 of all reactors in U.S. are PWR

57 Breeder Reactors & Nuclear Fission A type of nuclear fission in which nonfissionable (spent) U-238 is converted into fissionable Pu-239

58 Pros and Cons to Nuclear Energy

59 Breeder Reactors & Nuclear Fission Pros Makes more fissionable fuel than it uses Has potential to generate electricity for our country for centuries to come Cons Uses liquid sodium as its coolant which has its own safety and weapons concerns liquid sodium reacts explosively with water liquid sodium burns spontaneously in air loss of this coolant would certainly result cause a loss of containment and release of radiation into the atmosphere

60 Pros and Cons of Nuclear Energy Pros Less of an immediate environmental impact compared to fossil fuels Carbon-free source of electricity May be able to generate H-fuel Cons Generates radioactive waste Many steps require fossil fuels (mining and disposal) Expensive

61 Pros and Cons of Nuclear Energy

62 Cost of Electricity from Nuclear Energy Cost is very high 20% of US electricity is from Nuclear Energy Affordable due to government subsidies Expensive to build nuclear power plants Long cost-recovery time Fixing technical and safety issues in existing plants is expensive

63 Safety Issues

64 Safety Issues in Nuclear Power Plants Meltdown (most likely disaster) At high temperatures the metal encasing the uranium fuel can melt, releasing radiation cooling systems fail causing overheating Probability of meltdown is low Public perception is that nuclear power is not safe Sites of major accidents: Three Mile Island Chernobyl (Ukraine)

65 Three-Mile Island most serious reactor accident in US 50% meltdown of reactor core Containment building kept radiation from escaping No substantial environmental damage No human casualties Elevated public apprehension of nuclear energy Led to cancellation of many new plants in US

66 Chernobyl worst accident in history 1 or 2 explosions destroyed the nuclear reactor Large amounts of radiation escaped into atmosphere Spread across large portions of Europe

67 Chernobyl Radiation spread was unpredictable and uneven Death toll is 10, ,000

68 Nuclear Energy and Nuclear Weapons 31 countries use nuclear energy to create electricity These countries have access to spent fuel needed to make nuclear weapons Safe storage and handling of these weapons is a concern

69 Radioactive Waste

70 Radioactive Wastes Low-level radioactive waste Radioactive solids, liquids, or gases that give off small amounts of ionizing radiation High-level radioactive waste Radioactive solids, liquids, or gases that give off large amounts of ionizing radiation

71 Radioactive Wastes (solutions) Possible Long term solution to waste Deep geologic burial Yucca Mountain As of 2004, site must meet EPA million year standard (compared to previous 10,000 year standard) Other Possibilities: Above ground mausoleums Arctic ice sheets Beneath ocean floor Soviet Union was dumping radioactive waste into the oceans until very recently

72 Radioactive Waste Temporary storage solutions exist today In nuclear plant facility (require high security) Under water storage Above ground concrete and steel casks Need approved permanent options soon.

73 Case-In-Point Yucca Mountain 70,000 tons of highlevel radioactive waste Tectonic issues have been identified

74 Decommissioning Nuclear Power Plants Licensed to operate for 40 years Several have received 20-year extensions Power plants cannot be abandoned when they are shut down Three solutions Storage Entombment Decommissioning (dismantling)

75 Attitudes Towards Nuclear Power NIMBY - Not In My BackYard Citizens to not want a nuclear facility or waste disposal site near their home Dad- Decide, Announce, Defend Pronuclear advocates Based on the science, not fears

76 Future of Nuclear Energy

77 Fusion Fuel= isotopes of hydrogen

78 Fusion (the ideal solution) Way of the future? Produces no high-level waste Fuel is hydrogen Problems (currently unachievable) It takes very high temperatures (millions of degrees) to make atoms fuse Confining the plasma after it is formed plasma superheated ionized gas which has tendency to expand but (containers will not work) Scientists have yet to be able to create energy from fusion