Environmental Science: Energy Resources and Consumption

Fossil Fuels

  • Fossil Fuels:
    • Granberg 2009, art.com
    • Environmental Science: Topic 6.1 - Renewable and Nonrenewable Resources
    • Unit 6: Energy Resources and Consumption

Renewable vs. Non-Renewable Energy Sources

  • Renewable Energy Sources:
    • Can be replenished naturally at or near the rate of consumption and reused.
    • Examples: solar energy, wind power.
  • Non-Renewable Energy Sources:
    • Exist in a fixed amount and involve energy transformation that cannot be easily replaced.
    • Examples: coal, nuclear energy.
  • Enduring Understanding:
    • Humans use energy from various sources, leading to positive and negative consequences.
  • Learning Objective:
    • Identify differences between nonrenewable and renewable energy sources.
  • Essential Knowledge:
    • ENG-3.A.1: Nonrenewable energy sources are those that exist in a fixed amount and involve energy transformation that cannot be easily replaced.
    • ENG-3.A.2: Renewable energy sources are those that can be replenished naturally, at or near the rate of consumption and reused.

Nonrenewable Energy Resources

  • Definition: Fossil fuels and nuclear fuel supplies are considered nonrenewable because they cannot be replenished in our lifetimes
  • Supplies: Finite and can be used up
  • Categories: Fossil fuels and nuclear fuels
  • Involve energy transformation that cannot be easily replaced

Potentially Renewable Resources

  • Definition: Energy sources that can be regenerated indefinitely as long as not overharvested.
  • Examples: Forest trees, biofuels.

Nondepletable Resources

  • Definition: Renewable resources that cannot be used up and will typically not run out on human life scales.
  • Examples: Wind, solar, hydroelectric, wave, and geothermal energy.

Renewable Resources

  • Definition: Potentially renewable and nondepletable resources together are known as renewable energy resources.
  • Characteristics: Can be replenished naturally, at or near the rate of consumption, and reused.

Global Energy Consumption

  • Trends (1980-2016):
    • Energy use varies by world region.
  • Enduring Understanding:
    • Humans use energy from various sources, resulting in positive and negative consequences.
  • Learning Objective:
    • Describe trends in energy consumption.
  • Essential Knowledge:
    • ENG-3.B.1: Energy resource use is not evenly distributed between developed and developing countries.
    • ENG-3.B.2: The most widely used sources of energy globally are fossil fuels.
    • ENG-3.B.3: As developing countries become more developed, their reliance on fossil fuels for energy increases.
    • ENG-3.B.4: As the world becomes more industrialized, the demand for energy increases.
    • ENG-3.B.5: Availability, price, and governmental regulations influence which energy sources people use and how they use them.

Basic Units of Energy

  • SI Unit: Joule (J)
  • Common Multiples:
    • 1 Kilojoule (kJ) = 10^3 Joules
    • 1 Megajoule (MJ) = 10^6 Joules
    • 1 Gigajoule (GJ) = 10^9 Joules
    • 1 Terajoule (TJ) = 10^{12} Joules
    • 1 Exajoule (EJ) = 1 billion GJ

Developed vs. Developing Countries

  • Developed Countries:
    • Typically industrialized with a stable economy.
    • Examples: United States, Canada, Australia, Austria, France, Germany, Italy, Japan, United Kingdom.
  • Developing Countries:
    • Non-industrialized, poor, and seeking to develop resources.
    • Examples: India and China.

Developing Countries and Fuelwood

  • Many developing countries depend on fuelwood or other biomass for cooking and heating

Effects of Increasing Development

  • As developing countries become more developed, their use and reliance on fossil fuels increases
  • Some developing countries may bypass heavy fossil fuel use, moving directly to solar or other renewable energies
  • China is trying to reduce its fossil fuel consumption and shift towards solar and wind energy

Types of Energy Sources

  • Commercial Energy Sources:
    • Bought and sold (e.g., oil, coal, natural gas).
  • Subsistence Energy Sources:
    • Gathered by individuals for their own immediate needs (e.g., straw, fuelwood, dried animal dung).

Energy Trends in Developed Countries

  • Developed countries have more energy resources than developing countries.
  • Fossil fuels tend to be the most widely used energy source.
  • As the world becomes more industrialized, the demand for energy increases.
  • Fossil fuels are the largest type of energy consumed worldwide

Energy Trends in the United States

  • The U.S. still gets the largest proportion of its energy from fossil fuels
  • There have been increases in renewable energy in recent years.
  • Wind provides the most renewable energy, followed by wood and other biomass sources, and then hydroelectric.
  • Solar and geothermal currently make up the categories of renewables that are least utilized.

Energy Use in the U.S.

  • Energy is used in both residential and commercial buildings.
  • Areas for personal impact on reducing energy consumption.

Regional and Seasonal Energy Use

  • The Midwest and Southeastern U.S. primarily use coal in energy production.
  • The West and Northeast U.S. use a mix of nuclear, natural gas, and hydroelectric power
  • Highly populated areas use less coal due to air pollution
  • The Northern U.S. uses more energy in the winter for heating.
  • The Southern U.S. uses more energy in the summer for cooling.

Past Energy Consumption in the U.S.

  • Biomass (wood) was a primary energy source until the Industrial Revolution when coal became more extensively used
  • After World War II, petroleum and natural gas usage increased
  • Recent years have seen a shift away from coal to produce electricity with increased reliance on natural gas

Determining Energy Choices

  • Cost, availability, and ease of use are major concerns.
  • Costs include government regulation, extraction, processing, transportation, power plant construction, and operational costs
  • Energy costs depend on location and ease of access to particular energy sources

EROEI (Energy Return On Energy Investment)

  • Definition: The most direct way to account for the energy required to produce a fuel or energy source is to calculate the energy return on the energy investment
  • Concept: Measures how much energy is obtained from a source for every unit of energy expended on its production
  • A larger value for EROEI suggests a more efficient and more desirable type of energy

Why Gasoline is Used in Cars

  • Energy to mass ratio means that a smaller volume of gasoline is needed than many other types of fuels
  • Gasoline allows an engine to start and stop quickly

Drawbacks of Gasoline

  • Gasoline is highly refined from petroleum, which is costly.
  • Refineries release toxic air pollutants during fractional distillation.
  • Burning gasoline creates high amounts of air pollution, including CO_2, particulate matter, and nitrous oxides

Comparing Cost vs. Energy Produced (Weighted)

  • Most renewables can compete with fossil fuels when considering the weighted average of cost versus energy produced
  • The cost of some forms of renewable energy has dropped in recent years.

Energy Choices and Climate Change

  • Increased use of fossil fuels and greenhouse gases emitted during combustion has been linked to climate change.
  • Many developed countries are working to reduce their use of fossil fuels and replace them with renewable energy.
  • If accelerated climate change continues, it will affect food access, water resources, sea-level rise, extreme weather events, and disease distribution.

Health and Safety Concerns

  • Coal mining can be dangerous and deadly.
  • Burning fossil fuels creates and exacerbates air pollution Coal is cheap and abundant.

Coal and Death Rates from Energy Production

  • Coal is linked to the highest death rates (includes deaths from air pollution and accidents related to energy production).
  • Coal is the least safe form of traditional energy.

Topic 6.3 - Fuel Types and Uses

  • Conventional vs Non-Conventional Sources of Energy

Conventional vs. Non-Conventional Sources of Energy

  • Conventional:
    • Coal
    • Wood
    • Nuclear Energy
  • Non-Conventional:
    • Solar Energy
  • Enduring Understanding:
    • Humans use energy from various sources, resulting in positive and negative consequences.
  • Learning Objective:
    • Identify types of fuels and their uses.
  • Essential Knowledge:
    • ENG-3.C.1: Wood is commonly used as fuel in the forms of firewood and charcoal, especially in developing countries.
    • ENG-3.C.2: Peat is partially decomposed organic material that can be burned for fuel.
    • ENG-3.C.3: Three types of coal used for fuel are lignite, bituminous, and anthracite. Heat, pressure, and depth of burial contribute to the development of various coal types and their qualities.
    • ENG-3.C.4: Natural gas, the cleanest of the fossil fuels, is mostly methane.
    • ENG-3.C.5: Crude oil can be recovered from tar sands.
    • ENG-3.C.6: Fossil fuels can be made into specific fuel types for specialized uses.
    • ENG-3.C.7: Cogeneration.

Wood Use in the U.S.

  • Wood use has declined significantly in the U.S. over the last 200 years
  • Wood use is still locally important in some areas

Wood Use Around the World

  • Roughly half the world’s population in developing countries still burn wood and charcoal for heating and cooking
  • This can lead to deforestation and soil erosion

Ranking Coal by Heat Content

  • Peat < Lignite < Bituminous < Anthracite
  • Anthracite coal is the most desirable due to its high heat and low sulfur content and is also the rarest

Coal Formation

  • Peat turns into Lignite, then Bituminous, and finally Anthracite
  • Anthracite coal is the most desirable due to its high heat and low sulfur content and is also the rarest

Coal Abundance

  • Coal is the world’s most abundant fossil fuel
  • Coal has provided the greatest amount of electricity generation in the U.S. for many years
  • Coal power plants are gradually being replaced by natural gas fired power plants

Coal as a Dirty Fuel

  • Coal (besides peat) is the dirtiest fossil fuel to burn
  • Sulfur dioxide, nitrogen oxide, carbon dioxide, and particulate matter are all waste products of coal-fired power plants
  • Mercury and radioactive materials are released when coal is burned
  • amount of coal used for electricity generation in the U.S. has steadily declined from 2007 to now

Coal Reserves

  • About 1/4 of the world’s proven coal reserves are found in the United States
  • Identified coal reserves in the U.S. should last around 300 years or longer if we cut back on our use of them
  • The 4 nations with the largest quantities of proven coal reserves are the U.S., Russia, China, Australia, and India
  • Coal is the conventional fossil fuel resource that the world as a whole has the largest supply of

Advantages and Disadvantages of Coal

  • Advantages:
    • Ample supplies (225-900 years)
    • Energy-dense
    • Plentiful
    • High net energy yield
    • Easy to exploit by surface mining
    • Technological demands are small
    • Low cost (with huge subsidies)
    • Easy to handle and transport
    • Well-developed mining and combustion technology
    • Needs little refining
    • Air pollution can be reduced with improved technology
  • Disadvantages:
    • Severe land disturbance, air pollution, and water pollution
    • Contains impurities
    • High land use
    • Releases impurities into air when burned
    • Trace metals in coal
    • Combustion produces SO_2 and other air pollutants
    • Severe threat to human health
    • High CO_2 emissions
    • Ash is left behind
    • Releases radioactive particles and toxic mercury into air

Natural Gas

  • In its underground gaseous state, natural gas is a mixture of 80-95% methane (CH_4), the simplest hydrocarbon.
  • 5 to 20% is ethane, propane, and butane
  • Conventional natural gas lies above most reservoirs of crude oil
  • Like oil, natural gas was formed from fossil deposits of phytoplankton and animals buried on the seafloor for millions of years and subjected to high temperatures and pressures

Composition of Natural Gas

  • Propane and butane are liquefied and removed as liquefied petroleum gas (LPG) when a natural gas field is tapped
  • The rest of the gas (mostly methane) is dried, cleaned, and pumped into pressurized pipelines for distribution
  • Liquefied natural gas (LNG) can be shipped in refrigerated tanker ships

Natural Gas is Cleaner Than Coal

  • Natural gas has a high net useful energy yield and is the cleanest-burning fossil fuel.
  • Largest uses are for electricity generation and industrial processes in the U.S.
  • Also used for residential heating, clothes dryers, stoves, and water heaters

Natural Gas – A Transition Fossil Fuel

  • Experts predict an increased use of natural gas during this century as we transition to more renewable sources of energy
  • Natural gas may be "cleaner" burning, but that doesn’t mean it’s clean
  • Natural gas (CH4) has 25 times more warming potential than carbon dioxide (CO2)
  • The residence time is the length of time a molecule of gas is expected to remain in the atmosphere and is around 8-10 years for methane

Advantages and Disadvantages of Natural Gas

  • The combustion of natural gas emits about half as much carbon as coal: considered as a potential bridge between an economy that runs mostly on coal and one that runs entirely on renewables

Fracking and Natural Gas

  • Fracking or hydraulic fracturing is the process of drilling down into the Earth before a high-pressure water mixture is directed at the rocks to release the gas inside
  • Water, sand, and chemicals are injected into the rock at high pressure, which allows the gas to flow out to the head of the well

Pros and Cons of Fracking

  • Many people say the pros do not outweigh the harm and that we should transition to renewable energy quickly

Petroleum

  • Petroleum is a gooey liquid consisting primarily of hydrocarbon compounds with small amounts of sulfur, oxygen, and nitrogen impurities
  • It took millions of years and several lucky geological events for oil to form

Disadvantages of Oil

  • Using oil increases the release of heat-trapping carbon dioxide
  • Air pollutants harm people and other species
  • Groundwater can be contaminated with brine and other byproducts of drilling
  • Oil spills are always a possibility

Environmental Costs of Petroleum

  • Oil leaking from pipes or wells
  • Transporting oil around the world with possible accidents and spills
  • Trace metals that are released during combustion
  • Waste oil released into the environment

Petroleum Refining

  • Crude oil is transported to a refinery by pipeline, truck, or ship.
  • At the refinery, it is heated and distilled in gigantic columns to separate it into components with different boiling points
  • The distillation of crude oil can produce asphalt, heating oil, diesel oil, gasoline, etc.

Volatile Compounds

  • Volatile components are those with a tendency to vaporize (turn into a gas)
  • The most volatile compounds distilled from petroleum are those that are highest on the distillation column (like natural gas and gasoline)
  • The least volatile compounds distilled from petroleum are asphalt related products

Why Petroleum is a High-Value Fuel

  • High energy value per unit volume
  • Ability to start and stop quickly
  • Easily transported
  • The primary use is gasoline for transportation

Crude Oil

  • Crude oil can be recovered from tar sands, which are a combination of clay, sand, water, and bitumen
  • This is considered an unconventional source of petroleum
  • Rocks like shale that are fracked for natural gas are known as unconventional sources

Net Useful Energy Yield

  • Shale oil and tar sands have lower net useful energy yields than conventional oil deposits
  • Producing crude oil from tar sands also releases large quantities of air pollution, creates waste-disposal ponds, and uses a lot of energy and water
  • Before 2000, it wasn’t economically feasible to mine tar sands – now, with oil resources depleting, Canada has been actively mining them

Synfuels or Synthetic Fuels

  • Coal can be converted to gaseous and liquid fuels that burn cleaner than coal, but the costs are high
  • Producing and burning synfuels adds more carbon dioxide to the atmosphere than burning coal
  • Synthetic fuels have a large potential supply and can be used as vehicle fuel BUT they have a low net energy yield
  • Synfuels have lower air pollution when burned than coal

Distribution of Natural Energy Resources

  • Natural Gas
  • Petroleum
  • Coal

Distribution of Coal Reserves

  • United States: 271.7 billion tons
  • Australia: 90.4 billion tons
  • China: 126.2 billion tons
  • Russia: 172 billion tons

Distribution of Gas Reserves

  • Russia: 1,659 trillion cubic feet

Distribution of Oil Reserves

  • Middle East: 720.7 billion barrels

Topic 6.4 – Distribution of Natural Energy Resources

  • Enduring Understanding:
    • Humans use energy from a variety of sources, resulting in positive and negative consequences.
  • Learning Objective:
    • Identify where natural energy resources occur.
  • Essential Knowledge:
    • ENG-3.D.1: The global distribution of natural energy resources, such as ores, coal, crude oil, and gas, is not uniform and depends on regions' geologic history.

Abundant Elements in Earth's Crust

  • The crustal abundance of 4 elements makes up greater than 88% of the Earth’s crust
  • The four elements that make up most of Earth’s crust include: oxygen, silicon, aluminum, and iron

Gold in Michigan

  • When rock develops fractures, water from Earth’s surface dissolves valuable metals like gold, silver, and tantalum (used in cell phones)
  • These metals form concentrated deposits called veins
  • There is gold in the Western Upper Peninsula of Michigan– although abandoned today, there is still gold present but it costs more to extract it than what it is worth

Hydrothermal Vents

  • Rich hydrothermal deposits of gold, silver, zinc, and copper are found as sulfide deposits in the deep-ocean floor and around black smokers
  • They form when mineral-rich superheated water shoots out of vents in solidified magma on the ocean floor
  • After mixing with cold seawater, black particles of metal ore precipitate out and build up chimney-like ore deposits around the vent

Mining of Extinct Hydrothermal Vents

  • Right now it costs too much to extract the minerals from extinct hydrothermal vents
  • There is some evidence that the copper, silver, and gold found in the Keweenaw Peninsula of Michigan’s Upper Peninsula are from ancient hydrothermal vents where the Earth’s crust was diverging

Coal Distribution in U.S.

  • The U.S. has the world’s greatest amount of coal deposits
  • The Western U.S. and the Appalachian region of the Eastern U.S. have abundant coal
  • Michigan has coal in the central part of the Lower Peninsula, but it hasn’t been actively mined for many years

Coal Distribution Worldwide

  • U.S. has the most coal, followed by Russia, China, Australia, and India

Petroleum and Natural Gas Formation

  • Petroleum and natural gas form over millions of years from the decomposition, deep burial, intense pressure, and heat of organic matter
  • Petroleum and natural gas can become trapped underground by impermeable layers that keep it from rising to Earth’s surface

Structural Petroleum Trap

  • Petroleum and natural gas form over millions of years from the partial decomposition, deep burial, intense pressure, and heat
  • After oil and natural formed some of it migrated through tiny pores in the surrounding rock: some migrated until it was caught under impermeable layers of rock or clay where it was trapped

Oil Reserves Worldwide

  • Venezuela, Saudi Arabia, Canada, Iran, and Iraq are the countries with the largest proved oil reserves

Natural Gas Reserves Worldwide

  • Russia, Iran, Qatar, United States, and Saudi Arabia have the largest natural gas reserves

Uranium Formation

  • Uranium is thought to have formed in supernovae over 6 billion years ago or from the merger of neutron stars
  • Uranium later became enriched in Earth’s continental crust
  • Its slow radioactive decay provides the main source of heat inside the Earth, causing convection and plate tectonic activity
  • Carnotite (yellow) and Uraninite are ores commonly mined for the uranium they contain.

Uranium Reserves Worldwide

  • Australia, Kazakhstan, Canada, Russia, South Africa, and Namibia have the greatest uranium reserves

Unequitable Distribution of Energy Resources

  • Different regions of the world have access to different renewable and nonrenewable natural resources based on their geographic location and past geologic processes
  • Access contributes to a place’s economic development, political relationships, and culture

Topic 6.5 - Fossil Fuels

  • Fossil Fuels

Topic 6.5 - Fossil Fuels

  • Enduring Understanding:
    • Humans use energy from a variety of sources, resulting in positive and negative consequences.
  • Learning Objective:
    • Describe the use and methods of fossil fuels in power generation.
  • Essential Knowledge:
    • ENG-3.E.1: The combustion of fossil fuels is a chemical reaction between the fuel and oxygen that yields carbon dioxide and water and releases energy.
    • ENG-3.E.2: Energy from fossil fuels is produced by burning those fuels to generate heat, which then turns water into steam. That steam turns a turbine, which generates electricity.
    • ENG-3.E.3: Humans use a variety of methods to extract fossil fuels from the earth for energy generation.
  • Learning Objective:
    • Describe the effects of fossil fuels on the environment.
  • Essential Knowledge:
    • ENG-3.F.1: Hydrologic fracturing (fracking) can cause groundwater contamination and the release of volatile organic compounds.

Formation of Fossil Fuels

  • Fossil fuels are formed from biological material that became fossilized millions of years ago
  • Fuels from this source provide most of the energy used in both developed and developing countries
  • The vast majority of the fossil fuels we use (coal, oil, and natural gas) came from deposits of organic matter that were formed 50 million to 350 million years ago

Aerobic vs. Anaerobic Conditions

  • When organisms die, decomposers break down most of the dead biomass aerobically (with oxygen) and it quickly reenters the food web
  • In anaerobic (without oxygen) environments, a large amount of detritus may build up quickly
  • Under these conditions, decomposers cannot break down all of the detritus
  • As this material is buried under succeeding layers of sediment and exposed to heat and pressure, the organic compounds within it are chemically transformed into high-energy solid, liquid, and gaseous components that are easily combusted

Nonrenewable Energy Resources

  • Fossil fuels cannot be replenished once used, making them nonrenewable
  • Factors determining energy use rates include resources available and affordable
  • Environmental impacts are an increasingly considered factor in energy-use decisions

Complete Combustion

  • In complete combustion, oxygen combines with a hydrocarbon to form water and carbon dioxide and produces heat
  • Fuels are combusted to make energy

Incomplete Combustion

  • Incomplete combustion takes place when not enough O_2 is present, so “leftover” carbon gets released at soot and CO (carbon monoxide)

Energy Carrier (Electricity)

  • Coal, oil, and natural gas are primary sources of energy
  • Electricity is a secondary source of energy, obtained from the conversion of a primary source
  • Electricity is an energy carrier, moving and delivering energy in a convenient, usable form
  • Approximately 40% of the energy consumed in the U.S. is used to generate electricity. About 13% of this energy is available for end uses due to conversion losses during the electricity generation process

Electricity as Clean Energy

  • Electricity is clean at the point of use.
  • When electricity is produced by combustion of fossil fuels, pollutants are released at the location of its production.
  • Regardless of what fuel is used, all thermal power plants work in the same basic way–they convert the potential energy of a fuel into electricity

Thermal Power Plant

  • Coal (also natural gas or petroleum can be used) is delivered to a boiler, where it is burned
  • The energy is transferred to water to produce steam
  • The kinetic energy is transferred to the blades of a turbine

Electricity Generation

  • Steam turns the turbine, which turns the generator to generate electricity
  • Electricity is transported along transmission lines (electrical grid) and connects with end users
  • After steam passes through the turbine it is condensed back into water.

Coal Extraction

  • Coal is removed by either surface or underground mining
  • Surface mining uses machinery to remove overburden in strips.
  • Area strip mining is used where the terrain is fairly flat.

Overburden

  • In surface mining, mechanized equipment strips away the soil and rock that lies on top of the mineral deposits being removed–this material is referred to as the overburden
  • The overburden is sometimes referred to as mining spoils or tailings

Overburden Disposal

  • The overburden is filled in the trench that the mineral deposit once filled
  • A new cut is made parallel to the previous ones and the process is repeated over the entire site
  • Area strip mining leaves spoil banks, which are wavy and erodible hills of rubble

Advantages and Disadvantages of Coal

  • Advantages:
    • Energy-dense
    • Plentiful
    • Easy to exploit by surface mining
    • Technological demands are small
    • Economic costs are low
    • Easy to handle and transport
    • Needs little refining
  • Disadvantages:
    • Contains impurities
    • Release impurities into air when burned
    • Trace metals in coal
    • Combustion produces SO_2 and other air pollutants
    • Ash is left behind
    • Carbon is released into the atmosphere, which contributes to climate change

Coal Ash

  • After burning coal anywhere from 3 to 20% remains behind after burning as ash
  • The Kingston Fossil Plant ash/water spill near Knoxville took 5 years and at least 1 billion dollars to clean up.

Petroleum (Crude Oil)

  • Petroleum is a liquid mixture of hydrocarbons (such as oil, gasoline, and kerosene), water, and sulfur that occurs in underground deposits
  • Liquid petroleum that is removed from the ground is known as crude oil
  • The word petroleum is typically used synonymously with oil, although technically, petroleum is a compound that contains many hydrocarbons and can be distilled into oil, kerosene, and gasoline
  • Petroleum products are more suitable for mobile combustion applications, such as in vehicles.

Petroleum Formation

  • Petroleum is formed from the remains of ocean-dwelling phytoplankton (microscopic algae) that died 50 million to 150 million years ago
  • Deposits of phytoplankton are found in locations where porous sedimentary rocks, such as sandstone, are capped by nonporous rocks
  • Petroleum forms over millions of years and fills the pore spaces in the rock
  • Geologic events related to plate tectonics deform the rock layers so that they form a dome: the petroleum migrates upward toward the highest point in the porous rock, where it is trapped by the nonporous rock.

Petroleum Extraction

  • Petroleum producers must drill wells into a deposit and extract the petroleum with pumps
  • Petroleum must be transported to a petroleum refinery by pipeline if the well is on land, or by supertanker if the well is underwater.

Advantages and Disadvantages of Petroleum

  • Oil spills are a huge disadvantage of petroleum extraction
  • Some notable large oil spills in the United States include the 1989 Exxon Valdez oil tanker accident in Alaska and the Deepwater Horizon oil spill off the coast of Louisiana in 2010.

Natural Gas: Cleanest Fossil Fuel

  • Natural gas is 80 to 95% methane (CH_4) and 5 to 20% ethane, propane, and butane
  • Natural gas exists as a component of petroleum in the ground as well as in gaseous deposits found separately from petroleum
  • Natural gas is extracted in association with petroleum, and recently there has been exploration specifically for natural gas.

Uses of Natural Gas

  • The two largest uses of natural gas in the United States are for electricity generation and industrial process
  • Natural gas is used to manufacture nitrogen fertilizer and is used in homes as an efficient fuel for cooking, heating, and operating clothes dryers and water heaters

Other Uses of Natural Gas

  • Compressed natural gas can be used as a fuel for vehicles, but because it must be transported by pipeline, it is not accessible in all parts of the U.S.
  • Liquefied petroleum gas (LPG) is similar to natural gas but is in a liquid form and is a slightly less energy-dense substitute
  • LPG fuel can be transported via train or truck and stored at the point of use in tanks
  • Natural gas and LPG currently supply 29% of the energy used in the United States

Advantages and Disadvantages of Natural Gas

  • While natural gas releases less carbon dioxide than other fossil fuels when combusted, unburned natural gas (methane) that escapes into the atmosphere is a potent greenhouse gas because it is 25 times more efficient at absorbing infrared energy than CO_2
  • Natural gas leaks after extraction are a suspected contributor to the steep rise in atmospheric methane concentrations that was observed in the 1990s.