Lecture Outlines Chapter 20 Environment: The Science behind the Stories 4th Edition

1. Lecture Outlines Chapter 20 Environment:The Science behind the Stories 4th Edition Withgott/Brennan

2. Notes HW • Write each slide title on the left side of the paper • Summarize provided information on the right side of the paper • If there are slides with Objectives or “this lecture will help you understand” you do NOT need to write these. • Define any words or answer any questions or fill in the blanks when something appears in red. • Sometimes it is a question linked to a website you should view • Sometime there are comments written in purple. You do not need to write these. They are just my personal commentary  • Be prepared to discuss the questions at the end.

3. This lecture will help you understand: • Reasons for seeking alternative fuels • Contributions to world energy by alternative fuels • Nuclear energy • The social debate over nuclear power • Bioenergy • Hydroelectric power

4. Central Case: Sweden’s search for alternative energy • In 1980, Sweden’s people voted to phase out nuclear energy • The government has promoted hydroelectric, biomass, and wind power • Sweden will still use nuclear power instead of fossil fuels • Public support for nuclear power has increased

5. Alternatives to fossil fuels • What are both graphs telling us?

6. The U.S. relies on fossil fuels • The U.S. relies more on fossil fuels and nuclear power than other countries • The most widely used “conventional alternatives” to fossil fuels: • Nuclear, hydroelectric, and biomass energy • The use of conventional alternatives has been growing more slowly than fossil fuels • What do these graphs tell us?

7. Nuclear power • Nuclear energy occupies an odd and conflicted position in our debate over energy • It is free of air pollution produced by fossil fuels • Yet it has been clouded by weaponry, waste disposal, and accidents • Public safety concerns have led to limited development • The U.S. generates the most electricity from nuclear power • But only 20% of U.S. electricity comes from nuclear • France gets 76% of its electricity from nuclear power • First new plants in U.S. since 1978 were approved March 2012

8. Nuclear energy comes from uranium • Nuclear reactors = ? • Nuclear fuel cycle = the process that begins when uranium is mined • Radioisotopes = emit subatomic particles and high-energy radiation as they decay into lighter radioisotopes • They become stable isotopes • Uranium-235 decays into lead-207

9. Nuclear reactors use uranium-235 • Over 99% of uranium occurs as uranium-238 (238U) • Not used does not emit enough neutrons for a chain reaction • So we use 235U, with a half-life of 700 million years • 235U is enriched to 3% and formed into pellets (UO2) • Which are incorporated into fuel rods used in nuclear reactors • After several years in a reactor, uranium is depleted • The fuel no longer generates enough energy • Spent fuel can be reprocessed, but it is expensive • So it is disposed of as radioactive waste

10. Fission releases nuclear energy Nuclei of large atoms are bombarded with neutrons, releasing energy and neutrons • Nuclear energy =the energy that holds together protons and neutrons within the nucleus of an atom • Nuclear fission = ? • This chain reaction keeps a constant output of energy

11. Fission in reactors generates electricity • A moderator = a substance (water or graphite) that slows the neutrons bombarding uranium • Allows fission to begin in a nuclear reactor • Excess neutrons must be soaked up • Control rods ? • They are placed into the reactor among the water-bathed fuel rods • They are moved into and out of the water to control the rate of the reaction

12. A nuclear power plant • The reactor core is housed in a reactor vessel • The vessel, steam generator, and plumbing are located in a containment building • Containment buildings are constructed to prevent leaks of radioactivity due to accidents or natural catastrophes • Not all nations require containment buildings

13. A typical light water reactor= ? Draw all 5 parts

14. Breeder reactors make better use of fuel • Breeder reactors use 238U (normally a waste product) • A neutron is added to 238U to form 239Pu (plutonium) • They make better use of fuel, generate more power, and produce less waste • But breeder reactors are more dangerous than conventional reactors • Its highly reactive coolant raises the risk of explosions • Plutonium can be used in nuclear weapons • They also are more expensive • Most of the world’s breeder reactors have been closed

15. Fusion remains a dream Tremendous energy is released when deuterium and tritium are fused to form helium • Nuclear fusion = ? • Drives the sun’s output of energy and hydrogen (thermonuclear) bombs • If we could control fusion, we could produce vast amounts of energy from water

16. Nuclear power delivers energy cleanly • Nuclear power helps us avoid emitting 600 million metric tons of carbon each year • Power plants pose fewer health risks from pollution • They are safer for workers than coal-fired plants • Uranium mining damages less land than coal mining • Drawbacks of nuclear power: • Nuclear waste is radioactive • If an accident or sabotage occurs, the consequences can be catastrophic • The world has 436 operating nuclear plants in 30 nations

17. Nuclear power poses small risks # 3 • It poses the possibility of catastrophic accidents • The most serious accident in the U.S. = • Three Mile Island ? • Meltdown = coolant water drained from the reactor • Temperatures rose inside the reactor core … • Melting the metal surrounding the fuel rods … • Releasing radiation into the containment building • The emergency could have been far worse

18. Fukishma Second worst accident Tell me about it?!

19. Chernobyl was the worst accident yet 1986 explosion at the Chernobyl plant in Ukraine The most severe nuclear plant accident ever seen It was due to human error and unsafe design For 10 days, radiation escaped while crews tried to put out the fire More than 100,000 residents were evacuated 1000 square miles originally contaminated The landscape for 19 miles still remains contaminated The accident killed 31 people directly Thousands more became sick or developed cancer This is my crazy friend Bryan that visited Chernobyl on vacation

20. Waste disposal remains a problem Spent fuel rods and all other waste must be put in a safe location Where leaking radioactivity will not harm future generations Waste is held in temporary storage Spent rods are stored in water U.S. plants are running out of room Waste is now stored in thick barrels of steel, lead, and concrete

21. Waste storage at Yucca Mountain, Nevada • It is safer to store all waste in a central repository • It can be heavily guarded • Yucca Mountain, Nevada was chosen for this site • President Obama’s administration does not support it • So waste will remain at its current locations • Do you agree or disagree with the Presidents decision to not open Yucca Mtn? Explain

22. The future of nuclear energy • 75% of nuclear power plants in Western Europe will be retired by 2030 • Asian nations are increasing nuclear capacity • 56 plants are under construction • The U.S. nuclear industry has stopped building plants • Expanding nuclear capacity would decrease reliance on fossil fuels and cut greenhouse gas emissions

23. Bioenergy Bioenergy (biomassenergy) = energy obtained from organic material that makes up organisms Wood, charcoal, agricultural crops, manure, trees Bioenergy has great potential for addressing our energy challenges Over 1 billion people use wood for heat, cooking, and light

24. Overharvesting and developing new sources • Biomass is only renewable if it is NOT overharvested • Considered carbon neutral since no NET carbon increase • Overharvesting causes deforestation, erosion, and desertification • Heavily populated arid regions are most vulnerable • Cooking produces indoor air pollution • New biomass sources are being developed • Biopower = biomass sources are burned in power plants • Generating heat and electricity • Biofuels = liquid fuels used to power automobiles

25. Biopower generates electricity • Waste products of industries or processes • Woody debris, crop residues • Specifically grown crops (fast-growing willow trees, bamboo) • Biomass fuels provided about 4% of the energy used in the United States in 2010. Of this, about 46% was from wood and wood-derived biomass, 43% from biofuels (mainly ethanol), and about 11% from municipal waste

26. Scales of production • Farmers, ranchers, or villages use manure, wood waste, or biogas from digestion to generate electricity • Small household biodigesters work in remote areas • The U.S. has dozens of biomass-fueled power plants • Biomass power increases efficiency and recycling • It reduces CO2 emissions and dependence on imported fossil fuels • It is better for health and supports rural economies • But burning crops deprives the soil of nutrients • Relying only on bioenergy is not a sustainable option

27. Ethanol can power automobiles • Ethanol = ? • Ethanol is added to U.S. gasoline to reduce emissions • Flexible-fuel vehicles run on E-85 • 85% ethanol, 15% gasoline • 8 million cars are in the U.S. • Most gas stations do not yet offer this fuel

28. Ethanol may not be sustainable • Environmental scientists don’t like corn-based ethanol • Growing corn impacts ecosystems • Pesticides, fertilizers, irrigation • Takes up land that could be left unfarmed • Ethanol competes with food and drives up food prices • As farmers shifted to ethanol, corn for food dropped • Mexicans could not afford tortillas, and so they rioted • Growing corn requires energy for equipment, pesticides, and fertilizers • it is inefficient

29. Biodiesel powers engines • Biodiesel = produced from vegetable oil, cooking grease, or animal fats • Vehicles can run on 100% biodiesel • B20 = 20% biodiesel • Biodiesel reduces emissions • Its fuel economy is good • It costs a bit more than gasoline • Crops are specially grown • Using land, deforestation

30. Novel biofuels are being developed • Algae produce lipids that can be converted to biodiesel • Their carbohydrates can be fermented to make ethanol • It can be grown in ponds, tanks, possibly sewage treatment tanks • Algae grows fast and can be harvested every few days • It can use wastewater, ocean or saline water • It can capture CO2 emissions to speed its growth • Biofuels from algae are currently expensive • Cellulosic ethanol = produced from structural plant material (e.g., corn stalks) that has no food value • Switchgrass provides ethanol, habitat, and high EROI

31. Carbon neutral What is Carbon Neutral = ? I need to build one of these lawn mower cages for my bunny, LuLu.

32. Is bioenergy carbon-neutral ? • In principle, biomass energy releases no net carbon • Photosynthesis removes carbon that is released when biomass is burned • Burning biomass is not carbon-neutral: • If forests are destroyed to plant bioenergy crops • If we use fossil fuel energy (tractors, fertilizers, etc.) • The Kyoto Protocol gives incentives to destroy forests for biofuel crops • Only emissions from energy use (not land-use changes) are “counted” toward controlling emissions

33. Hydroelectric power (hydropower) • Hydropower = ? • Storage technique = water stored in reservoirs behind dams passes through the dam and turns turbines • Run-of-river approach generates electricity without disrupting the river’s flow • Flow water over a small dam that does not impede fish passage • Useful in areas away from electric grids

34. A typical dam: Draw a dam with its parts?

35. Hydroelectric power is widely used • Hydropower accounts for 2.2% of the world’s energy supply • And 15.6% of the world’s electricity production • Nations with large rivers and economic resources have used dams • However, many countries have dammed their large rivers • People want some rivers left undammed Made my family take pictures too

36. Hydropower is clean and renewable • Hydropower has two clear advantages over fossil fuels for producing electricity: • It is renewable: as long as precipitation fills rivers we can use water to turn turbines • It is clean: no carbon dioxide is emitted • Hydropower is efficient • It has an EROI of 10:1 • As high as any modern-day energy source

37. Hydropower has negative impacts • Damming rivers destroys wildlife habitats • Upstream areas are submerged • Downstream areas are starved of water • Natural flooding cycles are disrupted • Downstream floodplains don’t get nutrients • Downstream water is shallower and warmer • Periodic flushes of cold reservoir water can kill fish • Dams block passage of fish, fragmenting the river and reducing biodiversity • Large dams can cause earthquakes or collapse • http://www.youtube.com/watch?v=tgUxTLEa9Zw • Describe the video link above?

38. Hydropower may not expand much more • What is the world’s largest dam? • It displaced 1 million people • Generates as much electricity as dozens of coal-fired or nuclear plants • Most of the world’s large rivers have already been dammed • People have grown aware of the ecological impact of dams and resist more construction • Developing nations with rivers will increase hydropower

39. CH20-A • 1) How much of our global energy supply do nuclear power, bioenergy, and hydroelectric power contribute? How much of our global electricity do these three conventional energy alternatives generate? Why are the two numbers different? • 2) What is the difference between nuclear fusion and nuclear fission? Describe how nuclear fission works. How do nuclear plant engineers control fission and prevent a runaway chain reaction? • 3) In terms of greenhouse gas emissions, how does nuclear power, hydropower, and bioenergy compare to coal, oil, and gas? • 4) Describe each of the following events: Three Mile Island, Chernobyl, and Fukushima. What consequences resulted from each?

40. CH20-B • 5) List several concerns of the disposal of radioactive waste. What has been done so far about disposing of radioactive waste? • 6) List five sources of bioenergy. What is the world’s most used source of bioenergy? How does bioenergy usage vary between developed and developing countries? • 7) What are the benefits and drawbacks of bioenergy? • 8) Describe how a dam works. List 3 positives and 3 negatives associated with hydropower.

41. QUESTION: Review Which of the following is NOT considered a conventional alternative fuel? • Nuclear power • Biomass • Photovoltaic solar power • Hydropower

42. QUESTION: Review Which of the following is NOT considered a conventional alternative fuel? Nuclear power Biomass Photovoltaic solar power Hydropower

43. The reaction that drives the release of energy in nuclear power plants is: • Nuclear fission • Nuclear fusion • Control rods • Nuclear emergencies

44. The reaction that drives the release of energy in nuclear power plants is: Nuclear fission Nuclear fusion Control rods Nuclear emergencies

45. QUESTION: Review Why are nuclear power plants NOT supported in the United States? • Fears about accidents • Nuclear waste issues • High costs of building and maintaining plants • All are issues regarding nuclear energy

46. QUESTION: Review Why are nuclear power plants NOT supported in the United States? Fears about accidents Nuclear waste issues High costs of building and maintaining plants All are issues regarding nuclear energy

47. QUESTION: Review Yucca Mountain, Nevada, is the site selected for permanent radioactive waste disposal. Which of the following is NOT a reason for selecting this site? • It is remote. • Its wet climate should minimize water contamination. • The water table is deep underground. • It has minimal risk of earthquakes.

48. QUESTION: Review Yucca Mountain, Nevada, is the site selected for permanent radioactive waste disposal. Which of the following is NOT a reason for selecting this site? It is remote. Its wet climate should minimize water contamination. The water table is deep underground. It has minimal risk of earthquakes.

49. QUESTION: Review Ethanol in the United States is made mainly from ______, and is used to ______. • Soybeans, heat homes • Sugarcane, drive cars • Corn, drive cars • Willow trees, make electricity

50. QUESTION: Review Ethanol in the United States is made mainly from ______, and is used to ______. Soybeans, heat homes Sugarcane, drive cars Corn, drive cars Willow trees, make electricity