Environment

N O N R E N E W A B L E E N E R G Y

R E S O U R C E S

L E C T U R E 1 3

WHAT T YPES OF ENERGY RESOURCES DO WE USE?

90% of the commercial energy used in the world comes from

nonrenewable resources

• Oil, natural gas, and coal

Energy resources vary greatly in their net energy

• Amount of energy available from a resource minus the amount of energy needed to make it available

WHERE DOES THE ENERGY WE USE COME FROM?

N ET E N E R G Y : I T TA K E S E N E R G Y T O G ET E N E R G Y

• Each step in making energy available uses high-quality energy

– Example: oil must be found, pumped, transferred to a refinery, converted to gasoline, and delivered to consumers

• Net energy yield – Amount of high-quality energy available from a

resource minus the high-quality energy needed to make the energy available

NET ENERGY: IT TAKES ENERGY TO GET ENERGY • Net energy ratio

– Also called energy returned on investment

– Energy obtained per unit energy used to obtain it

• Energy density – Amount of energy available per kilogram of the

resource

NET ENERGY: IT TAKES ENERGY TO GET ENERGY

WE DEPEND HEAVILY ON OIL • Crude oil (petroleum)

– Contains combustible hydrocarbons

• Peak production – Time after which production from a well declines

• Crude oil cannot be used as it comes out of the ground – Must be refined using high-quality energy

– Petrochemicals–byproducts

WE DEPEND HEAVILY ON OIL

IS THE WORLD RUNNING OUT OF CRUDE OIL?

• Proven oil reserves–available deposits – 12 OPEC countries have 82% of the world’s proven crude

oil reserves

• These countries play a role in regulating global prices by agreeing to increase or decrease the amount produced

• Increasing shortage of cheap oil – Easy-to-reach deposits are quickly being depleted

O I L P R O D U C T I O N A N D C O N S U M P T I O N I N T H E U N I T E D S T AT E S

 U.S. commercial energy sources

• 80% from fossil fuels

• Largest portion comes from crude oil

 U.S. oil consumption exceeds domestic production

• Must import oil

 Recent rise in domestic production of tight oil from shale rock

• Likely to peak around 2020 and then decline

USE OF HEAV Y OIL HAS A HIGH ENVIRONMENTAL IMPACT

• Shale oil – Oil that is integrated within bodies of shale rock

• As opposed to being trapped between layers of rock

– Production involves mining, crushing, and heating the rock

• Extracts kerogen that can be distilled

USE OF HEAV Y OIL HAS A HIGH ENVIRONMENTAL IMPACT

• Oil sands (tar sands) another source of heavy oil – Contains bitumen

– Extensive deposits in Canada

• Extraction – Clear-cutting forests and strip-mining the land

– Drilling vertical wells

– Low net energy yield

– Requires much water

– Emits pollutants

NATURAL GAS IS A VERSATILE AND WIDELY USED FUEL • Liquefied petroleum gas (LPG)

– Stored in pressurized tanks for use in rural areas

• Liquefied natural gas (LNG) – Can be transported across oceans

– Medium net energy yield

– The United States currently exports to other nations

ENVIRONMENTAL EFFECTS OF NATURAL GAS PRODUCTION AND FRACKING IN THE U.S. • Fracking has several harmful environmental

effects – Requires enormous volumes of water

– Produces hazardous wastewater • Earthquakes could release wastewater into

groundwater

– Failure of well-casing cement causes contaminated ground water

• Natural gas fracking excluded from EPA regulations in 2005

CAN NATURAL GAS HELP TO SLOW CLIMATE CHANGE?

• Emits less CO2 per unit of energy than coal • Low price could slow shift to other renewable

energy resources

• Methane a much more potent greenhouse gas than CO2

– Drilling, production, and distribution of natural gas releases large quantities of methane

COAL IS A PLENTIFUL BUT DIRT Y FUEL

• Coal – Solid fossil fuel formed from remains of

land plants

• Burned in power plants – Generated 37% of the world’s electricity

in 2017

• Largest consumers of coal – China, India and the United States,

COAL IS A PLENTIFUL BUT DIRT Y FUEL

COAL IS A PLENTIFUL BUT DIRT Y FUEL • Environmental costs of burning coal

– Mining coal severely degrades land

– Water and air pollution

• Soot and CO2 • Trace amounts of mercury and radioactive materials

– Scrubbers remove some pollutants before they leave smokestacks

• Produces coal ash that must be safely stored

WE ARE NOT PAYING THE FULL COST OF USING COAL

• Harmful environmental and health costs – Not included in market price of coal-generated

electricity

• Ways to implement full-cost pricing – Phase out subsidies and tax breaks

– Require stricter air pollution controls

– Tax CO2 emissions

– Regulate coal ash as a hazardous waste

THE FUTURE OF COAL • U.S. coal use dropped 18% between 2007

and 2013 – Increased competition from natural gas,

wind, and solar power

– Grassroots political opposition

• Natural gas should overtake coal as largest electricity source by the 2030s

• U.S. coal producers are exporting coal – Use is expanding in India, China and other

countries in Africa and Asia

W E C A N C O N V E R T C O A L I N T O G A S E O U S A N D L I Q U I D F U E L S

• Conversion of solid coal to synfuels – Synthetic natural gas (SNG) by coal

gasification

– Methanol or synthetic gasoline by coal liquefaction

• Producing synfuels requires mining of 50% more coal

– Lower net energy and cost more to produce than coal

HOW DOES A NUCLEAR FISSION REACTOR WORK?

• Controlled nuclear fission reaction in a reactor – Light-water reactors

– Boil water to produce steam to spin a turbine

– Fueled by uranium ore mined from the earth’s crust

• Enriched uranium packed as pellets in fuel rods and fuel assemblies

– Control rods absorb neutrons

HOW DOES A NUCLEAR FISSION REACTOR WORK? • Water is the usual coolant • Containment shell around the core for

protection

• Emergency core cooling system • Typical cost to construct

– $9–27 billion

• United States, France, China and Russia – Leading producers of nuclear power in 2017

W H AT I S T H E N U C L EA R F U EL C Y C L E? • Mining the uranium • Processing and enriching the

uranium to make fuel

• Using it in a reactor • Safely storing the radioactive waste • Retiring the worn-out plant

– Storing its high- and moderate-level radioactive parts safely

DEALING WITH RADIOACTIVE NUCLEAR WASTES

• Rods must be replaced every three to four years

• Stored in water-filled pools for several years to cool

• Transferred to dry casks • Can be processed to remove plutonium

– Reprocessing reduces storage time from 240,000 years to about 10,000 years

– Costly and produces weapons material

D E A L I N G W I T H R A D I O A C T I V E N U C L E A R W A S T E S

• No permanent, secure repository exists today

• Retiring nuclear plants • Enormous costs

CONTROVERSY ABOUT THE FUTURE OF NUCLEAR POWER

• Nuclear reactors produced 20% of U.S. electricity in 2017 and 9% energy

• 59 new nuclear reactors under construction worldwide in 2018

• U.S. government provides subsidies, tax breaks, and insurance for the nuclear industry

• Accidents have dampened public confidence in nuclear power

CONTROVERSY ABOUT THE FUTURE OF NUCLEAR POWER • New technologies

– Advanced light-water reactors

• Built-in safety features

– Smaller, modular light water reactors

• Not yet built and evaluated

– Thorium-based reactors

• Less costly and safer