TYLER MILLER SCOTT E. SPOOLMAN

Transcription

1 LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER SCOTT E. SPOOLMAN 15 Nonrenewable Energy

2 Core Case Study: Is the United States Entering a New Oil and Natural Gas Era? Oil and natural gas Two most widely used natural resources in the U.S. Oil consumption is increasing New extractions from oil shale cause environmental harm Burning oil and natural gas will continue adding greenhouse gases to the atmosphere

3 Natural gas 28% Nuclear power 8% Coal 22% Oil 37% Hydropower 3% Geothermal, solar, wind biomass 2% Fig. 15-1a, p. 374

4 Fig. 15-1b, p. 374

5 15-1 What is Net Energy and Why Is It Important? Energy resources vary greatly in their net energy yields

6 Net Energy Is the Only Energy That Really Counts Net energy yield Total amount of useful energy available from a resource minus the energy needed to make the energy available to consumers Energy return on investment Energy obtained per unit energy used to obtain it

7 Net Energy Is the Only Energy That Really Counts (cont d.) First law of thermodynamics: It takes high-quality energy to get high-quality energy Pumping oil from ground, refining it, and transporting it Second law of thermodynamics Some high-quality energy is wasted at every step

8 Some Energy Resources Need Help to Compete in the Marketplace Cannot compete in open markets with alternatives that have higher net energy yields Need subsidies from taxpayers Nuclear power The uranium fuel cycle is costly

9 15-2 What Are the Advantages and Disadvantages of Oil? Conventional crude oil is abundant and has a medium net energy yield, but using it causes air and water pollution and releases greenhouse gases to the atmosphere Unconventional heavy oil from oil shale rock and tar sands exists in potentially large supplies but has a low net energy yield and a higher environmental impact than conventional oil

10 We Depend Heavily on Oil Crude oil (petroleum) Peak production time after which production from a well declines Global peak production for all world oil Crude oil cannot be used as it comes out of the ground Must be refined Petrochemicals byproducts

11 Lowest Boiling Point Gases Gasoline Aviation fuel Heating oil Diesel oil Naphtha Heated crude oil Grease and wax Furnace Asphalt Highest Boiling Point Fig. 15-4a, p. 377

12 Fig. 15-4b, p. 377

13 Are We Running Out of Conventional Oil? Availability determined by: Demand Technology Rate at which we remove the oil Cost of making oil available Market price Proven oil reserves available deposits Profitable

14 Are We Running Out of Conventional Oil? (cont d.) Unconventional heavy oil Higher environmental cost; production cost Three major options: Live with much higher oil prices Extend oil supplies Use other energy sources

15 Barrels of oil per year (billions) Projected U. S. oil consumption Arctic refuge oil output over 50 years Year Fig. 15-5a, p. 379

16 Fig. 15-5b, p. 379

17 Use of Conventional Oil Has Environmental Costs Land disruption, greenhouse gas emission, air pollution, water pollution, and loss of biodiversity Burning oil accounts for 43% of global CO 2 emissions

18 Trade-Offs Conventional Oil Advantages Ample supply for several decades Net energy yield is medium but decreasing Low land disruption Efficient distribution system Disadvantages Water pollution from oil spills and leaks Environmental costs not included in market price Releases CO 2 and other air pollutants when burned Vulnerable to international supply interruptions Fig. 15-6, p. 380

19 Case Study: Oil Production and Consumption in the United States The U.S.: Produces 9% of the world s oil and uses 23% of world s oil Has about 2% of world s proven oil reserves Imports 52% of its oil Should we look for more oil reserves? Extremely difficult Expensive and financially risky

20 Heavy Oil From Oil Shale Rock Oil shales contain kerogen After distillation shale oil 72% of the world s reserve is in arid areas of western United States Locked up in rock Lack of water needed for extraction and processing Low net energy yield

21 Fig. 15-7, p. 381

22 Heavy Oil from Tar Sands Tar sand contains bitumen Extensive deposits in Canada and Venezuela Oil sands have more oil than in Saudi Arabia Extraction Serious environmental impact before stripmining Low net energy yield

23 Fig. 15-8, p. 381

24 Trade-Offs Heavy Oils from Oil Shale and Tar Sand Advantages Large potential supplies Easily transported within and between countries Disadvantages Low net energy yield Releases CO 2 and other air pollutants when produced and burned Efficient distribution system in place Severe land disruption and high water use Fig , p. 382

25 15-3 What Are the Advantages and Disadvantages of Using Natural Gas? Conventional natural gas: Is more plentiful than oil Has a medium net energy yield and a fairly low production cost Is a clean-burning fuel However, producing it has created environmental problems

26 Natural Gas Is a Useful, Clean-Burning, but Not Problem-Free Fossil Fuel Natural gas 50-90% methane CH 4 Conventional natural gas Liquefied petroleum gas (LPG) Stored in tanks Liquefied natural gas (LNG) Low net energy yield Makes U.S. dependent upon unstable countries like Russia and Iran

27 Natural Gas Is a Useful, Clean-Burning, but Not Problem-Free Fossil Fuel (cont d.) The U.S. produces gas conventionally and from shale rock Increasing environmental problems with shale rock extraction

28 Trade-Offs Conventional Natural Gas Advantages Ample supplies Versatile fuel Medium net energy yield Emits less CO 2 and other air pollutants than other fossil fuels when burned Disadvantages Low net energy yield for LNG Production and delivery may emit more CO 2 and CH 4 per unit of energy produced than coal Fracking uses and pollutes large volumes of water Potential groundwater pollution from fracking Fig , p. 383

29 Case Study: Natural Gas Production and Fracking in the U.S. Fracking Drilling wells; using huge amounts of water, sand, and chemicals; dealing with toxic wastewater; transporting the natural gas Drinking water contaminated with natural gas can catch fire Fracking has several harmful environmental effects Fracking

30 Fig , p. 384

31 Fig , p. 385

32 Unconventional Natural Gas Coal bed methane gas In coal beds near the earth s surface; in shale beds High environmental impacts of extraction Methane hydrate Trapped in icy water; in permafrost environments; on ocean floor Costs of extraction is currently too high

33 15-4 What Are the Advantages and Disadvantages of Coal? Conventional coal is plentiful and has a high net energy yield at low costs, but using it results in a very high environmental impact We can produce gaseous and liquid fuels from coal, but they have lower net energy yields and using them would result in higher environmental impacts than those of conventional coal

34 Coal Is a Plentiful but Dirty Fuel Coal Solid fossil fuel Burned in power plants Generates 42% of the world s electricity Abundant world s largest coal reserves United States Russia China

35 Coal Is a Plentiful but Dirty Fuel (cont d.) Environmental costs of burning coal Severe air pollution Sulfur released as SO 2 Large amount of soot CO 2 Trace amounts of mercury and radioactive materials Coal Ash - LINK

36 Increasing moisture content Increasing heat and carbon 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 Fig , p. 386

37 Waste heat Coal bunker Turbine Cooling tower transfers waste heat to atmosphere Generator Cooling loop Pulverizing mill Boiler Condenser Filter Stack Ash disposal Fig a, p. 387

38 Fig b, p. 387

39 The Clean Coal Campaign Coal companies and energy companies has fought: Classifying carbon dioxide as a pollutant Classifying coal ash as hazardous waste Air pollution standards for emissions The 2008 clean coal campaign Note: there is no such thing as clean coal

40 Trade-Offs Coal Advantages Ample supplies in many countries Medium to high net energy yield Low cost when environmental costs are not included Disadvantages Severe land disturbance and water pollution Fine particle and toxic mercury emissions threaten human health Emits large amounts of CO 2 and other air pollutants when produced and burned Fig , p. 389

41 15-5 What Are the Advantages and Disadvantages of Using Nuclear Power? Nuclear power has a low environmental impact and a very low accident risk, but its use has been limited by: A low net energy yield, high costs, fear of accidents, and long-lived radioactive wastes Its role in spreading nuclear weapons technology

42 How Does a Nuclear Fission Reactor Work? Controlled nuclear fission reaction in a reactor Light-water reactors Very inefficient Fueled by uranium ore and packed as pellets in fuel rods and fuel assemblies Control rods absorb neutrons

43 How Does a Nuclear Fission Reactor Work? (cont d.) Water is the usual coolant Containment shell around the core for protection Water-filled pools or dry casks for storage of radioactive spent fuel rod assemblies

44 Uranium fuel input (reactor core) Small amounts of radioactive gases Control rods Containment shell Heat exchanger Steam Turbine Waste heat Generator LINK Hot coolant Hot water output Useful electrical energy about 25% Shielding Pressure vessel Coolant Moderator Coolant passage Water Condenser Cool water input Waste heat 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 a, p. 390

45 Fig b, p. 390

46 What Is the Nuclear Fuel Cycle? Mine the uranium Process the uranium to make the fuel Use it in the reactor Safely store the radioactive waste Decommission the reactor

47 Fuel assemblies Decommissioning of reactor Enrichment of UF 6 Fuel fabrication Reactor Conversion of U 3 O 8 to UF 6 (conversion of enriched UF 6 to UO 2 and fabrication of fuel assemblies) Uranium-235 as UF 6 Plutonium-239 as PuO 2 Spent fuel reprocessing Temporary storage of spent fuel assemblies underwater or in dry casks Low-level radiation with long half-life Mining uranium ore (U 3 O 8 ) Open fuel cycle today Recycling of nuclear fuel Geologic disposal of moderate and high-level radioactive wastes Fig , p. 392

48 Trade-Offs Conventional Nuclear Fuel Cycle Advantages Low environmental impact (without accidents) Disadvantages Low net energy yield High overall cost Emits 1/6 as much CO 2 as coal Low risk of accidents in modern plants Produces long-lived, harmful radioactive wastes Promotes spread of nuclear weapons Fig , p. 392

49 Fig , p. 393

50 Dealing with Radioactive Nuclear Wastes Is a Difficult Problem High-level radioactive wastes Must be stored safely for 10, ,000 years Where can it be stored? Deep burial: safest and cheapest option Would any method of burial last long enough? There is still no facility Shooting it into space is too dangerous

51 Dealing with Radioactive Nuclear Wastes Is a Difficult Problem (cont d.) Plans in the U.S. to build a repository for high-level radioactive wastes in the Yucca Mountain desert region (Nevada) Many problems including: Cost of $96 billion Rock fractures Earthquake zone Decrease national security

52 Dealing with Radioactive Nuclear Wastes Is a Difficult Problem (cont d.) Dealing with old nuclear power plants: Decommission or retire the power plant Dismantle the plant and safely store the radioactive materials Enclose the plant behind a physical barrier with full-time security until a storage facility has been built Enclose the plant in a tomb Monitor this for thousands of years

53 Can Nuclear Power Help Reduce Climate Change? Nuclear power plants no CO 2 emission Nuclear fuel cycle emits CO 2 Need high rate of building new plants, and a storage facility for radioactive wastes

54 Case Study: The 2011 Nuclear Power Plant Accident in Japan Triggered by a major offshore earthquake and resulting tsunami Four key human-related factors: No worst-case scenarios Seawalls too short Design flaws Relationship between plant owners and government

55 Fig , p. 396

56 Is Nuclear Fusion the Answer? Fusion Two isotopes fused together to form a heavier nucleus Releases energy Technology is very difficult to develop