Station 1: Fill in the Carbon Cycle Diagram using the word bank to the right. Each option is only used once.

Station 2: Coal Formation

Coal forms in swampy areas as the result of the decay of plants in the absence of oxygen. Biochemical changes produced by bacteria release oxygen and hydrogen and concentrate carbon. Coal goes through several changes during formation. With increased pressure and time, impurities and moisture are removed. In swamps where coal forms, other sediment, such as sand, clay, and silt, also is deposited. The weight of the sediment compresses the underlying organic matter. During this process, moisture and other materials are squeezed out, leaving a high carbon concentration.

The first stage in coal formation is material composed of about 75 to 90 percent water plus twigs, leaves, branches, and other plant debris. Although peat itself is not coal, it is an important fuel used in Ireland and the Soviet Union.

The second stage of coal formation is brown coal composed of compressed woody matter that has lost most of its moisture. It is used for local fuels in homes and industry. Germany uses its lignite to provide synthetic petroleum.

The third stage of coal formation is a dense, dark, brittle material that has lost all its moisture and most other impurities. It is ignited easily by a flame. Although bituminous coal is an efficient heating material, it produces a smoky yellow flame, ash, and sulfur compounds when it is burned. Strict emission laws have limited the amount of pollutants industries can release when this coal is burned. Bituminous coal is mined throughout the United States with major fields in the Appalachians, the Great Plains, and the Colorado Plateau.

Anthracite, sometimes called "hard coal," is the fourth and final stage in coal formation. Lignite coal and bituminous coal are sedimentary rocks. Anthracite is a metamorphic rock. It is found only in areas of mountain building where heat and pressure were great. Anthracite is the cleanest of all coals with the least impurities because it is mostly carbon. It does not produce as much heat as bituminous coal, but it is preferred because it burns cleaner and longer. Anthracite fields occur in northeastern Pennsylvania, Great Britain, and parts of the Soviet Union.

Station 3: Clean Coal Technology

Coal is the dirtiest of all fossil fuels. When burned, it produces emissions that contribute to global warming, create acid rain and pollute water. With all of the hoopla surrounding nuclear energy, hydropower and biofuels, you might be forgiven for thinking that grimy coal is finally on its way out.

But coal is no sooty remnant of the Industrial Revolution -- it generates half of the electricity in the United States and will likely continue to do so as long as it's cheap and plentiful [source: Energy Information Administration]. Clean coal technology seeks to reduce harsh environmental effects by using multiple technologies to clean coal and contain its emissions.

Coal is a fossil fuel composed primarily of carbons and hydrocarbons. Its ingredients help make plastics, tar and fertilizers. A coal derivative, a solidified carbon called coke, melts iron ore and reduces it to create steel. But most coal -- 92 percent of the U.S. supply -- goes into power production [source: Energy Information Administration]. Electric companies and businesses with power plants burn coal to make the steam that turns turbines and generates electricity.

When coal burns, it releases carbon dioxide and other emissions in flue gas, the billowing clouds you see pouring out of smoke stacks. Some clean coal technologies purify the coal before it burns. One type of coal preparation, coal washing, removes unwanted minerals by mixing crushed coal with a liquid and allowing the impurities to separate and settle.

Other systems control the coal burn to minimize emissions of sulfur dioxide, nitrogen oxides and particulates. Wet scrubbers, or flue gas desulfurization systems, remove sulfur dioxide, a major cause of acid rain, by spraying flue gas with limestone and water. The mixture reacts with the sulfur dioxide to form synthetic gypsum, a component of drywall.

Low-NOx (nitrogen oxide) burners reduce the creation of nitrogen oxides, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process. Electrostatic precipitators remove particulates that aggravate asthma and cause respiratory ailments by charging particles with an electrical field and then capturing them on collection plates.

Gasification avoids burning coal altogether. With integrated gasification combined cycle (IGCC) systems, steam and hot pressurized air or oxygen combine with coal in a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity. The heat energy from the gas turbine also powers a steam turbine. Since IGCC power plants create two forms of energy, they have the potential to reach a fuel efficiency of 50 percent [source: U.S. Department of Energy].

Where do the emissions go?Carbon capture and storage -- perhaps the most promising clean coal technology -- catches and sequesters carbon dioxide (CO2) emissions from stationary sources like power plants. Since CO2 contributes to global warming, reducing its release into the atmosphere has become a major international concern. In order to discover the most efficient and economical means of carbon capture, researchers have developed several technologies.

Flue-gas separation removes CO2 with a solvent, strips off the CO2 with steam, and condenses the steam into a concentrated stream. Flue gas separation renders commercially usable CO2, which helps offset its price. Another process, oxy-fuel combustion, burns the fuel in pure or enriched oxygen to create a flue gas composed

primarily of CO2 and water -- this sidesteps the energy-intensive process of separating the CO2 from other flue gasses. A third technology, pre-combustion capture, removes the CO2 before it's burned as a part of a gasification process.

After capture, secure containers sequester the collected CO2 to prevent or stall its reentry into the atmosphere. The two storage options, geologic and oceanic, must contain the CO2 until peak emissions subside hundreds of years from now. Geologic storage involves injecting CO2 into the earth. Depleted oil or gas fields and deep saline aquifers safely contain CO2 while un-minable coal seams absorb it. A process called enhanced oil recovery already uses CO2 to maintain pressure and improve extraction in oil reservoirs.

Ocean storage, a technology still in its early stages, involves injecting liquid CO2 into waters 500 to 3,000 meters deep, where it dissolves under pressure. However, this method would slightly decrease pH and potentially harm marine habitats. All forms of CO2 storage require careful preparation and monitoring to avoid creating environmental problems that outweigh the benefits of CO2 containment.

Since alternative forms of energy cannot yet replace a power source as cheap and plentiful as coal, clean coal technology promises to mitigate the increasingly severe climactic effects of coal emissions. Utility companies and businesses do not, however, always accept technology purely for the sake of the environment -- the technology must first make economic sense.

Cleaning coal and sequestering its emissions significantly raises the per-BTU price of what would otherwise be an inexpensive fuel. While selling byproducts like gypsum or commercial CO2 for sodas and dry ice can offset the price of clean coal technologies, a charge on carbon could make emission-reduction financially realistic.

Station 4: Crude Oil: Energy Source Fact File!

What is crude oil? How does crude oil generate electricity? Is crude oil a fossil fuel or a renewable?

Description

Crude oil is a dark liquid. It is found in reservoirs deep under the ground.

How was it formed?

Millions of years ago the world’s oceans were filled with plants and plankton. When these died they fell to the bottom of the seas. Over millions of years, these remains were buried under layers of sand and mud. Heat and pressure turned the remains into oil and natural gas.

Where do you find crude oil?

Oil reserves can be found all over the world, including the North Sea, Saudi Arabia, Russia, the United States, Iran, Iraq and China.

How is it made into electricity?

The oil is burned to heat water and produce steam. This steam propels the blades of a turbine. This is attached to a generator, which produces

What are the advantages of using crude oil?

Oil can easily be transported by a network of pipelines. Oil-fired power stations can, in theory, be built almost anywhere.

What are the disadvantages of using crude oil?

Oil is a non-renewable source of energy. This means that one day we will probably run out of crude oil.

Burning oil produces carbon dioxide gas. This is a greenhouse gas that contributes towards climate change.

Burning oil can pollute the air. Much of our oil has to be imported and it is becoming more and more expensive as reserves

reduce and imports increase. Producing electricity from crude oil is expensive compared to other fossil fuels such as coal

or gas.

Station 5: Nuclear Energy

Nuclear energy is sometimes called atomic energy. However, atoms can be the source of both nuclear and chemical energy. Nuclear energy involves the atom's nucleus; chemical energy involves the atom's electrons—subatomic particles that surround the nucleus. Pound for pound, a nuclear fuel (a material used as a source of nuclear energy) will produce several million times as much energy as a chemical fuel such as gasoline. Nuclear fuels yield so much energy that even a heavy ship such as an aircraft carrier powered by nuclear energy can operate many years without refueling.

How Nuclear Energy Is ReleasedFission

The fission of a heavy atom usually results in the formation of two lighter nuclei of approximately equal mass and in the release of several neutrons. The total mass of the fission products is less than the mass of the original nucleus; the "lost" mass has been converted into energy. The fissioning of a single uranium atom releases about 200 MeV of energy; about 177 MeV of this total is the kinetic energy (energy of motion) of the fission products, the remainder is radiant energy in the form of gamma rays. The average binding energy of the two lighter nuclei formed by fission is higher than the average binding energy of the original nucleus.

Although several types of heavy nuclei can be made to fission by bombarding them with neutrons, only three—those of uranium 235, uranium 233, and plutonium 239—are relatively easy to split and can be produced in quantity. The fission of all the nuclei contained in one kilogram of uranium 235 would yield about 23,000,000 kilowatt-hours of energy.

Uranium 235 occurs in nature, but forms less than one per cent of naturally occurring uranium. For commercial use, the uranium 235 content of natural uranium is usually increased, a process called uranium enrichment. Plutonium 239 and uranium 233, which do not occur in nature, are created in nuclear reactors. When the nucleus of one element changes into the nucleus of another element, it is known as transmutation.

Chain Reactions

On the average, two or three neutrons are released in each individual fission reaction. In a given quantity of matter containing fissionable material, some of the neutrons will cause the splitting of other fissionable nuclei, some will escape, and some will be captured (absorbed) by nuclei that do not undergo fission. If, on the average, at least one neutron from each fission reaction causes one other nucleus to undergo fission, the sequence of fission reactions is self-sustaining and is called a chain reaction.

The quantity of material required for a chain reaction to occur is called the critical mass. It varies with the nature and shape of the fissionable material. The bombarding particle causes the fission material to undergo fission. In most nuclear reactors, neutrons are used as bombarding particles. The target material is the substance that is bombarded; in most cases it is uranium. This is because uranium can release neutrons constantly, keeping up a flow of energy.

In a fission weapon, a quantity of fissionable material in excess of the critical mass is brought together very rapidly, and almost every neutron released in each fission reaction causes another nucleus to fission. As a result,

the number of fission reactions increases so rapidly that within a fraction of a second most of the nuclei have undergone fission and a vast quantity of energy is released.

In a nuclear reactor, on the other hand, the fissionable material is dispersed within other matter so that such a rapid, explosive reaction will not occur. The chain reaction in a nuclear reactor is controlled so that, on the average, just one neutron from each fission reaction causes another nucleus to undergo fission.

Moderators

Slow-moving neutrons are captured by fissionable nuclei several hundred times more easily than are fast-moving neutrons. The neutrons that are released when fission occurs move very fast, but a moderator may be used to slow them down. Typical moderators are ordinary water, heavy water (water that contains deuterium, a rare and heavy form of hydrogen, in place of ordinary hydrogen), beryllium, paraffin, or graphite.

When a fast neutron passes through a moderator, it collides with the moderator's atoms. Each collision reduces the neutron's speed. By the time the neutron has passed through the moderator and reached the fissionable material, its speed has been reduced enough so that it can be readily captured. Moderators must be able to reduce the speed of fast neutrons rapidly without an excessive number of collisions, and must be poor absorbers of slow neutrons.

Power Reactors

Power reactors use the heat produced by nuclear fission to form steam. In a nuclear power plant (as opposed to power plants that burn coal or petroleum), the steam is used to drive turbines that generate electricity. Many large nuclear plants generate more than 1,000 megawatts (1,000 million watts) of electricity. In a nuclear ship, the steam is used to drive a turbine that turns the ship's propellers. The different parts of a nuclear reactor are housed in different parts of the nuclear plant. One building contains the nuclear reactor proper, while other structures contain the turbines and other parts. Within the plant grounds are storage facilities for spent fuel.

Most power reactors use ordinary water as the coolant. They are called light-water reactors to distinguish them from reactors that use heavy water as a moderator. In light-water reactors, the reactor core is surrounded by the coolant under pressure within a container called the pressure vessel. The nuclear fuel is enriched uranium containing 2 to 4 per cent uranium 235. For use in the fuel rods, the uranium is converted into uranium dioxide.

There are two major types of light-water reactors.

In boiling-water reactors, the water heated in the core boils, forming steam. The steam is fed through pipes from the pressure vessel to the turbine. It is then cooled, condensing into water, which is pumped back to the core.

In pressurized-water reactors, the water is kept under very high pressure so that it cannot turn into steam as it is heated in the core. The heated water is pumped from the pressure vessel to a heat exchanger, where it flows through a system of narrow pipes surrounded by water. The hot, pressurized water gives up its heat to the water outside the pipes. As it is heated, this water boils, forming steam that is fed to the turbine. The steam is then condensed into water and returned to the heat exchanger. Meanwhile, the pressurized water circulates back to the pressure vessel, where it picks up more heat from the core.

Station 6: What is renewable energy?Unlike fossil fuels, which are finite, renewable energy sources regenerate.

There are five commonly used renewable energy sources:

Biomass Biomass is organic material that comes from plants and animals, and it is a renewable source of energy. Biomass contains stored energy from the sun. Plants absorb the sun's energy in a process called photosynthesis.

When biomass is burned, the chemical energy in biomass is released as heat. Biomass can be burned directly or converted to liquid biofuels or biogas that can be burned as fuels

Hydropower Hydropower is the largest renewable energy source for electricity generation in the United States. In 2016,

hydropower accounted for about 6.5% of total U.S. utility-scale electricity generation and 44% of total utility-scale electricity generation from all renewable energy.

Because the source of hydroelectric power is water, hydroelectric power plants are usually located on or near a water source.

Geothermal The word geothermal comes from the Greek words geo (earth) and therme (heat). Geothermal energy is heat

within the earth. People can use this heat as steam or as hot water to heat buildings or to generate electricity.

Geothermal energy is a renewable energy source because heat is continuously produced inside the earth

Wind Wind is caused by uneven heating of the earth's surface by the sun. Because the earth's surface is made up of

different types of land and water, it absorbs the sun's heat at different rates. One example of this uneven heating is the daily wind cycle.

During the day, air above the land heats up faster than air over water. Warm air over land expands and rises, and heavier, cooler air rushes in to take its place, creating wind. At night, the winds are reversed because air cools more rapidly over land than it does over water.

Today, wind energy is mainly used to generate electricity. Water pumping windmills were once used throughout the United States and some still operate on farms and ranches, mainly to supply water for livestock

Solar The sun has produced energy for billions of years and is the ultimate source for all of the energy sources and

fuels that we use today. People have used the sun's rays (solar radiation) for thousands of years for warmth and to dry meat, fruit, and grains. Over time, people developed devices (technologies) to collect solar energy for heat and to convert it into electricity.

An example of an early solar energy collection device is the solar oven (a box for collecting and absorbing sunlight). In the 1830s, British astronomer John Herschel used a solar oven to cook food during an expedition to Africa. People now use many different technologies for collecting and converting solar radiation into useful heat energy for a variety of purposes.

Solar photovoltaic (PV) devices, or solar cells, change sunlight directly into electricity. Small PV cells can power calculators, watches, and other small electronic devices. Arrangements of many solar cells in PV panels and arrangements of multiple PV panels in PV arrays can produce electricity for an entire house. Some PV power plants have large arrays that cover many acres to produce electricity for thousands of homes.

What role does renewable energy play in the United States?

Up until the mid-1800s, wood supplied nearly all of the nation's energy needs. As more consumers began using coal, petroleum, and natural gas, the United States relied less on wood as an energy source. Today, the use of renewable energy sources is increasing, especially biofuels, solar, and wind.

In 2016, about 10% of total U.S. energy consumption was from renewable energy sources (or about 10.2 quadrillion British thermal units (Btu)—1 quadrillion is the number 1 followed by 15 zeros). About 55% of U.S. renewable energy use is by the electric power sector for producing electricity, and about 15% of U.S. electricity generation was from renewable energy sources in 2016.

Renewable energy plays an important role in reducing greenhouse gas emissions. When renewable energy sources are used, the demand for fossil fuels is reduced. Unlike fossil fuels, non-biomass renewable sources of energy (hydropower, geothermal, wind, and solar) do not directly emit greenhouse gases.

The consumption of biofuels and other non-hydroelectric renewable energy sources more than doubled from 2000 to 2016, mainly because of state and federal government mandates and incentives for renewable energy. The U.S. Energy Information Administration (EIA) projects that the use of renewable energy in the United States will continue to grow through 2040.

Why don't we use more renewable energy?In general, renewable energy is more expensive to produce and to use than fossil fuel energy. Favorable renewable resources are often located in remote areas, and it can be expensive to build power lines from the renewable energy sources to the cities that need the electricity. In addition, renewable sources are not always available:

Clouds reduce electricity from solar power plants. Days with low wind reduce electricity from wind farms. Droughts reduce the water available for hydropower.