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Environmental Science

Mr. Bugoni

Lesson 93

Sources of Energy

&

Coal, Natural Gas, and Oil (Part 1)

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Objectives:

• Define the term fossil fuels.

• Identify the energy sources that we use.

• Describe the nature and origin of coal, and evaluate its extraction and use.

• Describe the nature and origin of natural gas, and evaluate its extraction and use.

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Define the term fossil fuels.

Fossil Fuels

Forms of stored solar energy created from incomplete biological decomposition of dead organic matter. Include coal, crude oil, and natural gas.

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Identify the energy sources that we use.• A variety of renewable and nonrenewable energy

sources are available to us.• Since the industrial revolution, nonrenewable fossil

fuels have become our primary sources of energy.− Oil, Natural Gas, and Coal

• Fossil fuels are formed very slowly…− Buried organic matter is transformed by…

− heat− pressure− anaerobic decomposition

• In evaluating energy sources, it is important to compare…− Amount of energy obtained from the fuel, to− Amount of energy invested in its extraction.

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We use a variety of energy sources• We use these energy sources in our homes, our machinery, to fuel

our vehicles, and provide the comfort and conveniences • A great deal of energy emanates from Earth’s core, enabling us to

harness geothermal power • An immense amount of energy resides within the bonds among

protons and neutrons in atoms, and this energy provides us with nuclear power

• Most of our energy comes from the Sun - Solar radiation- Photosynthesis- Fossil fuels = highly combustible substances formed from the

remains of organisms

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Fossil fuels are our dominant source of energy

• We use oil, coal, and natural gas • Fossil fuels have replaced biomass as our dominant source of

energy • The high-energy content of fossil fuels makes them efficient to

burn, ship, and store • These fuels generate electricity = a secondary form of energy that

is easier to transfer and apply to a variety of uses

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Resources are renewable or nonrenewable

• Renewable energy = supplies of energy will not be depleted by our use

- Sunlight, geothermal energy, and tidal energy • Nonrenewable energy = at our current rates of

consumption we will use up Earth’s accessible store of these sources in a matter of decades to centuries

- Oil, coal, natural gas, nuclear energy

- To replenish the fossil fuels we have depleted so far would take millions of years

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Fossil fuels are indeed created from fossils

• Fossil fuels we burn today were formed from the tissues of organisms that lived 100-500 million years ago

• Organic material is broken down in an anaerobic environment = one that has little or no oxygen

- Bottoms of deep lakes, swamps, and shallow seas

• Organic matter is eventually converted into crude oil, natural gas, or coal

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Fossil fuel reserves are unevenly distributed

• Some regions have substantial reserves, whereas others have very few

• How long a nation’s reserves will last depends on:

- How much the nation extracts, uses, and exports

- Nearly 67% of the world’s proven reserves of crude oil lie in the Middle East

- The U.S. possesses more coal than any other country

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Developed nations consume lots of energy

• People in developed regions consume far more energy than those in developing nations

• Industrialized nations divide their energy use evenly between transportation, industry, and other uses

- Developing nations use energy for subsistence activities (agriculture, food preparation, and home heating)

- Developing nations use manual or animal energy instead of fossil fuels

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Regions vary greatly in energy consumption

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It takes energy to make energy

• To harness, extract, process, and deliver energy requires substantial inputs of energy

- Roads, wells, vehicles, storage tanks

• Net energy = the difference between energy returned and energy invested

- Net energy = energy returned – energy invested

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Energy returned on investment (EROI)

• Energy returned on investment (EROI) = energy returned/energy invested

- Higher ratios mean we receive more energy than we invest

- Ratios decline when we extract the easiest deposits first and now must work harder to extract the remaining reserves

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Describe the nature and origin of coal, and evaluate its extraction and use.

• Coal is our most abundant fossil fuel.- First used widely for heating homes- Now used principally for electricity generation

• Coal is mined…− underground− strip mined from the land surface

• Coal comes in different types and varieties.

• Combustion of coal is high in contaminants and pollution.

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Coal

• The world’s most abundant fossil fuel

• Coal = organic matter (woody plant material) that was compressed under very high pressure to form dense, solid carbon structures

- Very little decomposition occurred

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Coal use has a long history

• The Romans used coal for heating in the second and third centuries in Britain

• The Chinese have used coal for 2,000 - 3,000 years

• Commercial mining began in the 1700s

- The invention of the steam engine expanded coal’s market

• Coal helped drive the Industrial Revolution and the steel industry

• In the 1880s, people used coal to generate electricity

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Coal is mined from the surface and below ground

• Subsurface mining = underground deposits are reached by digging networks of tunnels deep underground

• Strip mining = heavy machinery removes huge amounts of earth to expose and extract the coal

- Mountaintop removal = in some cases, entire mountaintops are cut off to obtain the coal

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Two forms of coal mining

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Coal varies in its qualities

• Coal varies from place to place

- Water quantity and amount of potential energy it has

• Peat = organic material that is broken down anaerobically but remains wet, near the surface and not well compressed

- Widely used as a fuel in Britain

• Additional pressure turns peat into coal

- Lignite = least compressed

- Sub-bituminous and bituminous

- Anthracite = most compressed; has the most energy

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Coal contains impurities

• Sulfur, mercury, arsenic, and other trace metals

• Sulfur content depends on whether coal was formed in salt water or freshwater

- Coal in the eastern U.S. is high in sulfur because it was formed in marine sediments

• When high-sulfur coal is burned, it released sulfate air pollutants, which contribute to smog and acidic deposition

- Mercury can bioaccumulate

• Ways to reduce pollution must be found

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Describe the nature and origin of natural gas, and evaluate its extraction and use.

• Natural gas consists mostly of methane and is formed in two ways...- Biogenic gas: formed by the underground anaerobic

decomposition of organic matter.- Thermogenic gas: formed by pressure and heat.

• Use of natural gas is growing.− Burns cleaner than oil or coal

• Natural gas also occurs with oil and coal deposits.

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Natural gas

• The fastest growing fossil fuel in use today

• Provides 25% of global commercial energy consumption

• World supplies are projected to last about 60 more years

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Natural gas is formed in two ways

• Natural gas = consists of methane (CH4) and other volatile hydrocarbons

• Biogenic gas = created at shallow depths by bacterial anaerobic decomposition of organic matter

- “swamp gas”

• Thermogenic gas = results from compression and heat deep underground

• Kerogen = organic matter that results when carbon bonds begin breaking

- Source material for natural gas and crude oil

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Natural gas is often wasted

• Coalbed methane = from coal seams, leaks to the atmosphere during mining

• In remote oil-drilling areas, natural gas is flared: simply burned off

- In Alaska, gas captured during oil drilling is being reinjected into the ground for future use

• Landfills produce biogenic natural gas

- Operators are capturing and selling it

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Natural gas has only recently been widely used

• Plutarch called naturally burning gas in Iraq “eternal fires”

• The first commercial extraction occurred in 1821 but was only used locally, because it could not be transferred safely

• First used to light street lamps, then for heating and cooking

• After thousands of miles of pipes were laid, natural gas transport became safer and more economical

• Liquefied natural gas (LNG) = liquid gas that can be shipped long distances in refrigerated tankers

• Russia has the largest deposits, and Russia and the U.S. lead the world in production and consumption, respectively

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Natural gas extraction becomes more challenging

• The first gas fields simply required an opening and the gas moved upward

• Most remaining fields require pumping by horsehead pumps

• Most accessible reserves have been depleted

- Gas is accessed by sophisticated techniques such as fracturing, which pumps high-pressure salt water into rocks to crack them

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Offshore drilling produces much of our gas

• Drilling takes place on land and in the seafloor on the continental shelves

- Technology had to come up with ways to withstand wind, waves, and currents

- Platforms are either strong fixed platforms or floating platforms

- 25% of our natural gas comes from offshore drilling

- Hurricanes can devastate drilling platforms, and prices rise accordingly