ENVIRONMENTAL SCIENCE Energy

Energy - 3 Main Ideas E resources should be evaluated on potential supplies how much net useful E they provide Environmental impact of using them

Energy - 3 Main Ideas Using a mix of renewable energy: Sunlight Wind flowing water sustainable biofuels geothermal energy can drastically reduce pollution, greenhouse gas emissions, and biodiversity losses.

Energy - 3 Main Ideas Making transition to more sustainable E future requires sharply reducing E waste using a mix of environmentally friendly renewable E resources, including harmful environmental costs of E resources in their market prices.

Evaluating Energy Resources Energy from the sun Indirect forms of renewable solar energy Wind Hydropower Biomass Commercial energy Fossil fuels – non-renewable Nuclear – non-renewable

Evaluating Energy Resources 75% world’s commercial E comes from non-renewable fossil fuels. Rest comes from non-renewable nuclear fuel renewable sources

Coal Layers of coal Lignite Bituminous Anthracite Lowest Carbon Content Bituminous Layer used to generate electricity Anthracite Layer with the most Carbon

Increasing heat and carbon content Increasing moisture content Peat (not a coal) Lignite (brown coal) Bituminous (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Figure 13.9: Stages in coal formation over millions of years. Peat is a soil material made of moist, partially decomposed organic matter and is not classified as a coal, although it too is used as a fuel. The different major types of coal vary in the amounts of heat, carbon dioxide, and sulfur dioxide released per unit of mass when they are burned. 14

Coal Is a Plentiful But Dirty Fuel Used in electricity production Main use of coal today World’s most abundant fossil fuel U.S. reserves should last ~ 250 years Sulfur and particulate pollutants Mercury and radioactive pollutants Also used to make Steel

Waste heat Cooling tower transfers waste heat to atmosphere Coal bunker Turbine Generator Cooling loop s Stack Pulverizing mill Condenser Filter Figure 13.10: Science: coal-burning power plant. Heat produced by burning pulverized coal in a furnace boils water to produce steam that spins a turbine to produce electricity. The steam is cooled, condensed, and returned to the boiler for reuse. Waste heat can be transferred to the atmosphere or to a nearby source of water. The largest coal-burning power plant in the United States, located in Indiana, burns three 100-car trainloads of coal per day. The photo shows a coal-burning power plant in Soto de Ribera, Spain. Question: Does the electricity that you use come from a coal-burning power plant? Boiler Toxic ash disposal Fig. 13-10, p. 306 16

Coal Is a Plentiful But Dirty Fuel Heavy carbon dioxide emissions Pollution control and environmental costs China major builder of coal plants

The Growing Problem of Coal Ash Highly toxic Black Lung Disease Often stored in ponds Ponds can rupture Groundwater contamination EPA: in 2009 called for classifying coal ash as hazardous waste Opposed by coal companies

Oil Oil Formation

https://visual.ly/community/infographic/science/surprising-products-we-get-crude-oil

How Long Will Crude Oil Supplies Last? Crude oil is the single largest source of commercial energy in world and U.S. Proven oil reserves Can be extracted profitably at today’s prices with today’s technology 80% depleted between 2050 and 2100

Barrels of oil per (billions) 14 13 12 11 10 Projected U.S. oil consumption 9 8 Barrels of oil per (billions) year7 6 5 4 Figure 13.4: The amount of crude oil that might be found in the Arctic National Wildlife Refuge, if developed and extracted over 50 years, is only a tiny fraction of projected U.S. oil consumption. In 2008, the DOE projected that developing this oil would take 10–20 years and lower gasoline prices at the pump by at most 6 cents per gallon. (Data from U.S. Department of Energy, U.S. Geological Survey, and Natural Resources Defense Council) 3 2 Arctic refuge oil output over 50 years 1 2000 2010 2020 2030 2040 2050 Year 24

US Oil Production and Use 93% of energy from fossil fuels 39% from crude oil Produces 9% of world’s crude oil Uses 25% of world production Has 2% of proven crude oil reserves

Oil Sand and Oil Shale Oil sand (tar sand) Bitumen Kerogen Shale Oil World reserves Major environmental problems

Natural Gas Is a Useful and Clean-burning Fossil Fuel Conventional natural gas Unconventional natural gas

Liquefied natural gas (LNG) Less CO2 emitted per unit of Energy than with crude oil, tar sand, shale oil World supply of conventional natural gas: 62-125 years Unconventional natural gas Coal-bed methane gas Methane hydrate

What Are Advantages and Disadvantages of Nuclear Energy? nuclear power fuel cycle: low environmental impact very low accident risk

What Are Advantages and Disadvantages of Nuclear Energy? …but limited because of: high costs low net energy yield long-lived radioactive wastes vulnerability to sabotage potential for spreading nuclear weapons technology.

How Does a Nuclear Fission Reactor Work? Light-water reactors Boil water to produce steam to turn turbines to generate electricity Radioactive uranium as fuel Control rods, coolant, and containment vessels

storage of radioactive Small amounts of radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Waste heat Heat exchanger Steam Turbine Generator Hot coolant Useful electrical energy About 25% Hot water output Pump Pump Coolant Pump Pump Waste heat Cool water input Figure 13.14: Science: light-water-moderated and -cooled nuclear power plant with a pressurized water reactor. Some nuclear plants withdraw water for cooling from a nearby source of water and return the heated water to that source, as shown here. Other nuclear plants that do not have access to a source of cooling water transfer the waste heat to the atmosphere by using one or more gigantic cooling towers, as shown in the inset photo of the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania (USA). A serious accident there in 1979 almost caused a meltdown of the plant’s reactor. Question: How does this plant differ from the coal-burning plant in Figure 13-10? Moderator Shielding Pressure vessel Coolant passage Water Condenser Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Water source (river, lake, ocean) Fig. 13-14, p. 310 36

Safety and Radioactive Wastes On-site storage of radioactive wastes Safety features of nuclear power plants Nuclear fuel cycle Reactor life cycle Large amounts of very radioactive wastes

Fig. 13-15, p. 311

Fig. 13-15, p. 311

of spent fuel assemblies underwater or in dry casks Decommissioning of reactor Fuel assemblies Reactor Enrichment of UF6 Fuel fabrication (conversion of enriched UF6 to UO2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies underwater or in dry casks Uranium-235 as UF6 Plutonium-239 as PuO2 Conversion of U3O8 to UF6 Spent fuel reprocessing Low-level radiation with long half-life Figure 13.16: Science: the nuclear fuel cycle. As long as a reactor is operating safely, the power plant itself has a fairly low environmental impact and a very low risk of an accident. But considering the whole nuclear fuel cycle, costs are high, radioactive wastes must be stored safely for thousands of years, several points in the cycle are vulnerable to terrorist attack, and the technology used in the cycle can also be used to produce material for nuclear weapons (Concept 13-3). Also, an amount of energy equal to about 92% of the energy content of the nuclear fuel is wasted in the nuclear fuel cycle. Question: Do you think the market price of nuclear-generated electricity should include all the costs of the fuel cycle or should governments pay much of these costs as they do now? Explain. Geologic disposal of moderate and high-level radioactive wastes Mining uranium ore (U3O8 ) Open fuel cycle today Recycling of nuclear fuel Fig. 13-16, p. 312 40

What Happened to Nuclear Power? Optimism of 1950s is gone Comparatively expensive source of power No new plants in U.S. since 1978 Disposing of nuclear waste is difficult Three Mile Island (1979)

Three Mile Island: Chernobyl March 28, 1979 near Harrisburg, Pa. stuck valve in cooling system. $500 million cleanup of site thru 1993. Chernobyl 26 April 1986 plume of highly radioactive smoke fallout. 50 to 200 thousand deaths.

Fukushima Daiichi nuclear disaster 11 March 2011 Reactors 1, 2 & 3 experienced full meltdown. Measurements taken by the Japanese science ministry and education ministry in areas of northern Japan 30–50 km from the plant showed radioactive caesium levels high enough to cause concern.[17] Food grown in the area was banned from sale. Based on worldwide measurements of iodine-131 and caesium-137, it was suggested that the initial daily release of those isotopes from Fukushima are of the same order of magnitude as those from Chernobyl in 1986[18][19], and that the total release of radioactivity is about one-tenth that from the Chernobyl disaster[20]; Tokyo officials temporarily recommended that tap water should not be used to prepare food for infants.[21][22] Plutonium contamination has been detected in the soil at two sites in the plant,[23] although further analysis revealed that the detected densities are within limits from fallout generated from previous atmospheric nuclear weapons tests.[24] Two workers hospitalized with non-life threatening radiation burns on 25 March had been exposed to between 2 and 6 Sv of radiation at their ankles when standing in water in Unit 3.[25][26][27] Follow up examination at 11 April from National Institute of Radiological Sciences was without confirmation.[28] Japanese officials initially assessed the accident as Level 4 on the International Nuclear Event Scale (INES) despite the views of other international agencies that it should be higher. The level was successively raised to 5 and eventually to 7, the maximum scale value.[29][30] The Japanese government and TEPCO have been criticized in the foreign press for poor communication with the public[31][32] and improvised cleanup efforts.[33] Foreign experts have said that a workforce in the hundreds or even thousands would take years or decades to clean up the area

Nuclear Power Is Vulnerable to Terrorist Acts Insufficient security On-site storage facilities U.S.: 161 million people live within 75 miles of an above-ground nuclear storage site

Dealing with Radioactive Wastes High-level radioactive wastes Long-term storage: 10,000–240,000 years Deep burial Detoxify wastes?

Case Study: Dealing with Radioactive Wastes in the United States Yucca Mountain, Nevada Concerns over groundwater contamination Possible seismic activity Transportation accidents & terrorism 2009: Obama ends Yucca funding

What Do We Do with Worn-Out Nuclear Power Plants? Decommissioning old nuclear power plants Dismantle power plant and store materials Install physical barriers Entomb entire plant Chernobyl sarcophagus

What Is the Future for Nuclear Power? Reduce dependence on foreign oil Reduce global warming Advanced light-water reactors Nuclear fusion How to develop relatively safe nuclear power with a high net energy yield?