EUES - Nonrenewable Energy Sources, Continued (Lesson)

Nonrenewable Energy Sources, Continued

Natural Gas

Natural gas, often known simply as gas, is composed mostly of hydrocarbon methane. The amount of natural gas being extracted and used in the United States is increasing rapidly.

Natural Gas Formation

Natural gas forms under the same conditions that create oil. Organic material buried in the sediments hardens to become a shale formation that is the source of the gas. Although natural gas forms at higher temperatures than crude oil, the two are often found together.

 

 

 

Watch below to see the formation of an oil and gas deposit that can be mined.

 

 

The largest natural gas reserves in the United States are in the Appalachian Basin, Texas, and the Gulf of Mexico region. California also has natural gas, found mostly in the Central Valley. In the northern Sacramento Valley and the Sacramento Delta, a sediment-filled trough formed along with a location where the crust was pushed together (an ancient convergent margin).

 

Natural Gas Use

Like crude oil, natural gas must be processed before it can be used as a fuel. Some of the chemicals in unprocessed natural gas are poisonous to humans. Other chemicals, such as water, make the gas less useful as a fuel. Processing natural gas removes almost everything except methane. Once the gas is processed, it is ready to be delivered and used. Natural gas is delivered to homes for uses such as cooking and heating. Like coal and oil, natural gas is also burned to generate heat for powering turbines. The spinning turbines turn generators, and the generators create electricity.

Consequences of Natural Gas Use

Natural gas burns much cleaner than other fossil fuels, meaning that it causes less air pollution. Natural gas also produces less carbon dioxide than other fossil fuels do for the same amount of energy, so its global warming effects are less.

Unfortunately, drilling for natural gas can be environmentally destructive. One technique used is hydraulic fracturing, also called fracking, which increases the rate of recovery of natural gas. Fluids are pumped through a borehole to create fractures in the reservoir rock that contains the natural gas. Material is added to the fluid to prevent the fractures from closing.

The damage comes primarily from chemicals in the fracturing fluids. Chemicals that have been found in the fluids may be carcinogens (cancer-causing), radioactive materials, or endocrine disruptors, which interrupt hormones in the bodies of humans and animals. The fluids may get into groundwater or may runoff into streams and other surface waters. Plus, fracking may cause earthquakes.

Coal: The Fossil Fuel that Started the Industrial Revolution

Coal, a solid fossil fuel formed from the partially decomposed remains of ancient forests, is burned primarily to produce electricity. Coal use is undergoing enormous growth as the availability of oil and natural gas decreases and costs increase. This increase in coal use is happening particularly in developing nations, such as China, where coal is cheap and plentiful.

Coal is black or brownish-black. The most common form of coal is bituminous, a sedimentary rock that contains impurities such as sulfur. Anthracite coal has been metamorphosed and is nearly all carbon. For this reason, anthracite coal burns more cleanly than bituminous coal.

 

Coal Formation

Coal forms from dead plants that settled at the bottom of ancient swamps. Lush coal swamps were common in the tropics during the Carboniferous period, which took place more than 300 million years ago. The climate was warmer then. Mud and other dead plants buried the organic material in the swamp, and burial kept oxygen away. When plants are buried without oxygen, the organic material can be preserved or fossilized. Sand and clay settling on top of the decaying plants squeezed out the water and other substances. Millions of years later, what remains is a carbon-containing rock that we know as coal.

Coal Use

Around the world, coal is the largest source of energy for electricity. The United States is rich in coal. California once had a number of small coal mines, but the state no longer produces coal. To turn coal into electricity, the rock is crushed into powder, which is then burned in a furnace that has a boiler. Like other fuels, coal releases its energy as heat when it burns. The heat from the burning coal boils the water in the boiler to make steam. The steam spins turbines, which turn generators to create electricity. In this way, the energy stored in the coal is converted to useful energy like electricity.

 

Global Coal Output as a Percentage of China (top producer) 2005

 

Consequences of Coal Use

For coal to be used as an energy source, it must first be mined. Coal mining occurs at the surface or underground by methods. Mining, especially underground mining, can be dangerous. In April 2010, 29 miners were killed at a West Virginia coal mine when gas that had accumulated in the mine tunnels exploded and started a fire.

Coal mining exposes minerals and rocks from underground to air and water at the surface. Many of these minerals contain the element sulfur, which mixes with air and water to make sulfuric acid, a highly corrosive chemical. If the sulfuric acid gets into streams, it can kill fish, plants, and animals that live in or near the water.

Biomagnification and Sources of Mercury

The diagram to the right shows another environmental consequence of burning coal, our primary fuel source for electrical power. Mercury, arsenic, sulfur, other heavy metals like cadmium, lead, and uranium as well as carbon dioxide, carbon monoxide, VOCs, particulates, and nitrogen and sulfur oxides are all produced from the combustion of coal.

How much is left?

The answer to that question depends on what we as a society are willing to do to get fossil fuels. How much are we willing to damage the environment to extract and transport fossil fuels? How much are we willing to raise atmospheric greenhouse gas levels and further alter climate? The Keystone Pipeline would bring crude oil from tar sands to the U.S., but for the time being, that project is on hold.

 

Fossil Fuel Reserves

Fossil fuels provide about 85% of the world's energy at this time. Worldwide fossil fuel usage has increased many times over in the past half-century (coal - 2.6x, oil - 8x, natural gas - 14x) because of population increases, because of increases in the number of cars, televisions, and other fuel-consuming uses in the developed world, and because of lifestyle improvements in the developing world.

 

Worldwide Oil Reserves

 

Alternative Fossil Fuels

As the easy-to-reach fossil fuel sources are depleted, alternative sources of fossil fuels are increasingly being exploited. These include oil shale and tar sands. An oil shale is a rock that contains dispersed oil that has not been collected in reservoirs. To extract the oil from the shale requires enormous amounts of hot water. Tar sands are rocky materials mixed with very thick oil. The tar is too thick to pump and so tar sands are strip-mined. Hot water and caustic soda are used to separate the oil from the rock.

The environmental consequences of mining these fuels, and of fossil fuel use in general, along with the fact that these fuels do not have a limitless supply, are prompting the development of alternative energy sources in some regions.

Nuclear Energy (Nuclear Fission)

Nuclear energy is produced by splitting the nucleus of an atom. This releases a huge amount of energy.

How Nuclear Power Plants Work

Nuclear power plants use uranium that has been concentrated in fuel rods. The uranium atoms are split apart when they are hit by other extremely tiny particles. These particles must be controlled or they would cause a dangerous explosion.

Nuclear power plants use the energy they produce to heat water. The water turns into steam, which causes a turbine to spin. This in turn produces electricity.

Conversion of Yellow Cake Uranium to Uranium Hexafluoride (UF6)

Nuclear Power as a Resource

Many countries around the world use nuclear energy as a source of electricity. For example, France gets about 80% of its electricity from nuclear energy. In the United States, a little less than 20% of electricity comes from nuclear energy.

Nuclear energy does not pollute. If there are no accidents, a nuclear power plant releases nothing but steam into the air. But nuclear energy does create other environmental problems. Splitting atoms creates dangerous radioactive waste. These wastes can remain dangerous for hundreds of thousands of years. Scientists and engineers are still looking for ways to keep this waste safely away from people.

Consequences of Nuclear Power

Nuclear power is clean. It does not pollute the air. However, the use of nuclear energy does create other environmental problems. Uranium must be mined. The process of splitting atoms creates radioactive waste. This waste may be dangerous for thousands or hundreds of thousands of years. As yet, there is no long-term solution for storing the radioactive waste.

 

 

For three decades new nuclear power plants were not built in the U.S. Accidents at Three Mile Island and Chernobyl, Ukraine made people nervous about harnessing nuclear power. Because nuclear energy is clean, nuclear power was making a comeback. But the 2011 disaster at the Fukushima Daiichi Nuclear Power Plant in Japan changed attitudes back. This accident seems to have resulted in a new fear of nuclear power. The disaster was caused by a 9.0 magnitude earthquake and tsunami. These events seriously damaged the plant.

Nuclear power is a controversial subject. Nuclear power has no pollutants. Nuclear power does not produce greenhouse gases. However, accidents do happen and they can be devastating. The long-term disposal of wastes is a problem that has not yet been solved. The future of nuclear power is murky.

Where could long-term nuclear waste go?

That's a very good question. For years, a waste facility was in development in Nevada. The site at Yucca Mountain was canceled due to public outcry. Now there is no facility for storing long-term nuclear waste from most sources. No facilities are currently being developed either.  

 

 

 

RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.