Alternatives to fossil fuels

1. Alternatives to fossil fuels • Global economy is powered by fossil fuels • These fuels also power ⅔ of electricity generation • Fossil fuels are limited and pollute • We need to shift

2. Conventional alternatives • We have alternatives to fossil fuels • More expensive in the short term when external costs are not included in prices • The most widely used “conventional alternatives” to fossil fuels: • Nuclear, hydroelectric, and biomass energy

3. Nuclear power • It is free of air pollution produced by fossil fuels • But 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

4. Fission releases nuclear energy • Nuclei of large atoms are bombarded with neutrons, releasing energy and more neutrons • Nuclear fission = the splitting apart of atomic nuclei • The reaction that drives the release of nuclear energy in power plants • This chain reaction keeps a constant output of energy

5. Nuclear energy comes from uranium

6. Nuclear reactors use uranium-235 • Over 99% of uranium occurs as uranium-238 (238U) • It does not emit enough neutrons for a chain reaction • So we use 235U • 235U is enriched to 3% and formed into pellets • Which are incorporated into fuel rods used in nuclear reactors • After several years in a reactor, uranium is depleted • Spent fuel can be reprocessed, but it is expensive • So it is disposed of as radioactive waste

7. Fission in reactors generates electricity • A moderator = a substance (water or graphite) that slows the neutrons bombarding uranium • Control rods = a metallic alloy that absorbs neutrons • 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

8. A typical light water reactor • Not all nations require containment buildings!

9. Fusion not yet feasible • Nuclear fusion = forces together small nuclei of lightweight elements under extremely high temperature and pressure • 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 • Check ITER.org

10. 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

11. Nuclear power goes bad rarely, but… • When it does, it’s bad • The most serious accident in the U.S. = Three Mile Island in Pennsylvania in 1979 • Meltdown = coolant water drained from the reactor • Temperatures rose inside the reactor core … • Melting the metal surrounding the fuel rods … • Releasing radiation

12. Chernobyl was the worst accident yet 1986 explosion and fire at the Chernobyl plant in Ukraine 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 The landscape for 19 miles still remains contaminated The accident killed 31 people directly Thousands more became sick or developed cancer

13. The Chernobyl accident The destroyed reactor was encased in a massive concrete sarcophagus, which is still leaking radioactive material

14. Radioactivity from Chernobyl spread widely Atmospheric currents carried radioactive fallout from Chernobyl across much of the Northern Hemisphere

15. Smaller-scale accidents have occurred • Western reactors are safer than Chernobyl • But smaller accidents have occurred • Aging plants require more maintenance and are less safe • Recent terrorist attacks raised fears that similar attacks could be carried out against nuclear plants • Or stolen radioactive material could be used in attacks • The U.S. “megatons to megawatts” program buys radioactive material from the former Soviet Union • Using it in power plants

16. Fukushima! • ~1/10 the radiation of Chernobyl

17. 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

18. U.S. storage of high-level radioactive waste • Waste is held at 125 sites in 39 states • 161 million citizens live within 75 miles of nuclear waste

19. Waste storage at Yucca Mountain, Nevada • It is safer to store all waste in a central repository • Yucca Mountain, Nevada was chosen for this site • Shut down for political reasons (Obama administration) • So waste will remain at its current locations

20. Dilemmas slow nuclear power’s growth Concerns over waste disposal, safety, and costs have affected nuclear power’s growth It is expensive to build, maintain, operate, and ensure the safety of nuclear facilities Decommissioning plants can be more expensive than construction Power plants serve less than half their expected lifetimes Electricity costs more than from coal and other sources Governments must subsidize nuclear power

21. The future of nuclear energy • 75% of nuclear power plants in Western Europe will be retired by 2030 • Some nations are rethinking this because of concerns over climate change • Asian nations are increasing nuclear capacity • Most of the 60 reactors under construction are in Asia • The U.S. nuclear industry has stopped building plants

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

23. Overharvesting and developing new sources • Biomass is only renewable if it is not overharvested • Overharvesting causes deforestation, erosion, and desertification • And burning indoors produces indoor air pollution • New biomass sources are being investigated • Biopower = biomass sources are burned in power plants • Generating heat and electricity • Biofuels = liquid fuels used to power automobiles

24. Biopower generates electricity • Waste products of industries or processes • Woody debris, crop residues • Specifically grown crops (fast-growing willow trees, bamboo) • Co-firing combines biomass and coal • Gasification turn biomass to a gas • Pyrolysis produces a liquid fuel

25. Scales of production • Farmers, ranchers, or villages use manure, wood waste, or biogas from waste digestion to generate electricity • Small household biodigesters work in remote areas • Burning crops deprives the soil of nutrients • Relying only on bioenergy is not a sustainable option

26. Ethanol can power automobiles • Ethanol = a biofuel made by fermenting carbohydrate-rich crops • Ethanol is added to U.S. gasoline to reduce emissions • In 2009, 10 billion gallons were made in the U.S. from corn • Congressional mandates will increase ethanol production

27. 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 • Its EROI ratio is about 1.5:1, so it is inefficient

28. Biodiesel powers engines • Biodiesel = produced from vegetable oil, cooking grease, or animal fats • Biodiesel reduces emissions • Its fuel economy is great • It costs a bit more than gasoline • In large scale, crops are specially grown • Using land, deforestation

29. Novel biofuels are being developed • Algae produce oils that can be converted to biodiesel • Can use them to make ethanol too • It can be grown in ponds, tanks, or photobioreactors • 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 • Cellulosic ethanol = produced from plant material that has no food value • Switchgrass provides ethanol, habitat, and high EROI

30. Two novel biofuels Algae! Switchgrass!

31. 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 to grow them (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

32. Hydroelectric power (hydropower) • Hydropower = uses the kinetic energy of moving water to turn turbines to generate electricity • Storagetechnique = 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

33. A typical dam

34. A run-of-river system

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 • The U.S. government built dams to employ people and help end the economic depression of the 1930s • Engineers exported their dam-building techniques

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

38. Hydropower may not expand much more • China’s Three Gorges Dam is the world’s largest dam • It displaced 1 million people • Generates as much electricity as dozens of coal-fired or nuclear plants • Problems… • Most of the world’s large rivers have already been dammed

39. QUESTION: Review Conventional alternative fuels: • Exert less environmental impact than fossil fuels but are currently not feasible • Are intermediate sources of fuel that can help us on our path towards sustainability • Are final sources of fuel that will give us energy independence • Are no longer available for widespread use

40. QUESTION: Review The reaction that drives the release of energy in today’s nuclear power plants is: • Nuclear fission • Nuclear fusion • Control rods • Nuclear emergencies

41. QUESTION: Review Why have nuclear power plants not been popular in the United States? • Fears about accidents or sabotage • Storage of nuclear waste is still not solved • High costs of building and maintaining plants • All are issues regarding nuclear energy

42. 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

43. QUESTION: Review Which of the following is an interesting future biofuel? • Corn • Algae • Nuclear • Shale oil

44. QUESTION: Review Which of the following forms of hydropower is least environmentally destructive? • The storage approach • Run-of-river approach • Bend-of-river approach • All of these are destructive forms and none should be used.

45. QUESTION: Weighing the Issues Given the choice of living next to a coal-burning power plant or nuclear plant, which would you choose? • The nuclear plant, because it’s cleaner. • The coal plant, because it won’t be as likely a target for terrorists. • Neither one; I’d move to another place. • Either one; I don’t care.

46. QUESTION: Interpreting Graphs and Data a) More corn is available for ethanol. b) More competition between food and fuel. c) Less land planted in corn. d) None of these. If ethanol in the United States continues to be produced from corn, a drawback suggested from this graph could be: