Lesson Plans and Resource Guide

2/12/04

Coal Energy:

Lesson Plans and Resource Guide

Authors:

Diane Little- Science Teacher

Janna Match- Reading Specialist

Coal Energy

Background Information

Introduction

As a society, we grapple continually with difficult questions relating to energy resources. As educators, it is vital that we teach our students to think critically about their choices. They must know that, along with the energy-producing benefits of each resource, there are potential liabilities. Public health and safety, efficiency, environmental impacts and economic ramifications all should be considered when making decisions. To come to reasonable conclusions, students need a working knowledge of each resource, including coal.

Coal, the most abundant fossil fuel in the U.S. and the world, has been used for thousands of years as a valuable natural resource. The U.S. has approximately 24% of all the world's known coal reserves. There are enough coal reserves worldwide to supply energy, at the current rate, for over 220 years. With the world's increasing need for energy, coal is a major resource in demand.

The objective of the following lesson plans is to educate elementary through high school students about the practices in developing this massive energy resource. The information, aligned with National Science Education Content Standards and Pennsylvania Academic Standards, will be presented in a hands-on, engaging manner. It will be balanced, coming from a variety of sources.

The lesson plans will investigate the following coal-related topics: formation and identification, mining, energy, environmental impacts and legislation. Also, they will explore advancements in the coal energy industry, including clean coal technologies, cogeneration, waste-coal usage and land reclamation.

Energy Resources

The necessities and luxuries in our everyday lives create the increasing demand for energy resources. The total world consumption of energy is approximately 400 quadrillion (one quadrillion = 1,000,000,000,000,000) BTUs annually. BTUs are British thermal units, which are a measure of heat energy. The heat produced by burning one wooden kitchen match is equal to about one BTU. The United States consumes close to 98 quadrillion BTUs per year, approximately twenty-five percent of the world’s energy supply. Projections indicate that by the year 2025, the world will use 640 quadrillion BTUs annually. These numbers either could rise or fall depending on legislation, weather and consumer choices.

Most of the energy consumed by the world comes from nonrenewable resources, which are limited in quantities and can be depleted. These resources are primarily fossil fuels: petroleum, coal and natural gas. Petroleum accounts for approximately 39% of the world’s energy consumption. Coal and natural gas each supply approximately 23%. Uranium is another nonrenewable energy resource used in nuclear power plants. It is used for approximately 7% of the world’s energy.

Renewable energy resources, of endless supply, account for approximately 8% of the world’s energy consumption. Hydroelectric power, derived from running water, is the most widely used form of renewable energy. These resources also include biomass (from plants, garbage and agricultural waste), solar, geothermal (heat energy within the earth) and wind. Researchers continue to study other sources of energy, among them nuclear fusion and a variety of hydrogen-based technologies.

Coal: A Fossil Fuel

Fossil fuels, fuels derived from plant and animal matter, formed naturally over long periods of time, at least thousands, perhaps millions, of years. These energy-producing fuels are the remains of ancient life that have undergone changes due to heat and pressure. The primary fossil fuels are coal, petroleum and natural gas. Together they account for 85% of the world's energy consumption.

Coal is a dark, combustible material formed, through a process known as coalification, from plants growing primarily in swamp regions. Layers of fallen plant material accumulated and partially decayed in these wet environments to form a spongy, coarse substance called peat. Over time, this material was compressed under sand and mud, and heated by the earth to be transformed into coal. Some scientists refer to coal as sedimentary rock. Coal is primarily composed of carbon, hydrogen, oxygen and nitrogen.

There are several ranks of coal, which are rated according to their carbon content and heating value. The heating value of coal is expressed in BTUs per pound. A precursor to the formation of coal is peat. Peat, with a heating value of approximately 4,500 BTUs, contains up to 60% carbon when dried. Peat hardens over time and under pressure into lignite, a cheap brown coal, containing approximately 70% carbon. Lignite has a heating value of approximately 7,000 BTUs. Sub-bituminous coal, with an approximate heating value of 9,300 BTUs contains about 78% carbon. Bituminous coal is a more developed coal and the most common type. With a heating value that ranges from approximately 11,250 – 14,350 BTUs, it contains about 85% carbon. The hardest and most expensive coal, anthracite, has a heating value of approximately 13,600 BTUs. It contains 92-95% carbon.

Coal Mining

The two main types of coal mining are surface (strip) mining and underground mining. Strip mining involves the removal of coal deposits close to earth's surface (usually no more than 100 feet from the surface). Topsoil and rocks are removed from the surface to expose the coal deposits. Explosives and heavy machinery are used to break up and remove layers of coal.

Underground mining involves the removal of coal deposits, often hundreds of feet below the earth's surface. (Some mines may be close to 2,000 feet deep.) Shafts or tunnels are dug into the coal layers and widened to allow room for the miners and coal cars or conveyor belts. Additional shafts may be excavated to increase air ventilation for the miners.

The history of coal mining is rife with tragic occurrences. Mining accidents, methane gas explosions, violence fueled by labor strikes, and respiratory ailments -primarily Black Lung Disease- were common in the past. Over 100,000 miners have been killed in coal-mining accidents in the U.S. since 1900. The United Mine Workers of America Union was formed in 1890 to promote safer working conditions. Years later, the U.S. Coal Mine Health and Safety Act of 1969 created strict standards for miner safety and health. New technologies in mining and safety regulations have greatly improved conditions for miners. Since 1993, there have been fewer than 370 accidental coal-mining fatalities. Since 1969, the number of fatalities related to Black Lung Disease has dropped by two-thirds. Still, between one and two thousand miners die each year from complications associated with this disease.

Coal Uses

Coal is used to generate heat, produce electricity, and make steel and industrial products. It is used worldwide as a fuel, second only to petroleum as the most consumed energy resource.

Simple burning of coal produces heat for homes and industries. Coal is a major fuel for producing electricity. The coal is burned to turn water into steam. The steam turns the blades of a turbine, which drives a generator to produce electricity. Coal is used for approximately 50% of the U.S. electricity production and 40% of the world's electricity.

Coke is a hard material produced when coal is heated without air at approximately 1000o C (1832o F). Coke (which is almost pure carbon) is used to smelt iron ore for the production of steel. Coal tar, a sticky black liquid derived from coke, is used for paving roads and tarring roofs. The extraction and distillation of coal tar into separate compounds produces a variety of products for making drugs, plastics, paints and synthetic fibers.

Coal gas, composed of methane and hydrogen, is a by-product of burning coal. Coal gas was used in the 1940s for residential lighting and cooking, but it was phased out because it was expensive. Today, coal gasification processes are being developed to be more cost effective. Methanol is now being developed and used as a fuel for engines.

Coal Energy: Environmental Impacts and Modern Technology

The mining and burning of coal has a long history of negative environmental impacts. Land, water and air pollution standards were not part of the coal industry's early history. Over the past several decades, attempts have been made to mitigate these effects.

In 1955, the Air Pollution Control Act (now known as the Clean Air Act) was created. This legislation raised the nation’s awareness of industrial coal pollution.

In 1977, the Surface Mining Control and Reclamation Act (SMCRA) was passed, requiring that coal-mining sites be restored to natural areas or productive land. By that time, there were over one million acres of abandoned coal mine sites in the United States, among them underground mines, strip-mining pits, acid mine drainage sites and coal refuse (culm) banks. These sites have had a detrimental effect on water quality, public health and safety, economics and aesthetics. Since the SMCRA, mine operators have been required to pay taxes. These taxes are placed into a fund that pays for reclamation of lands abandoned prior to SMCRA’s enactment. The SMCRA also has mandated that today’s coal companies pay directly for reclamation of lands affected by their own operations.

In 1978, the Public Utility Regulatory Policies Act (PURPA) was enacted. This federal law requires regulated utility companies to buy power from qualified independent generators.

Regulations and environmental awareness have helped to improve the coal industry, but problems still exist. Due to loopholes in the amended Clean Air Acts of 1970 and 1977, older, often larger, coal-fired power plants are exempt from instituting many emissions upgrades. These plants continue to pollute at rates up to ten times greater than newer ones. Meanwhile, newer operations have been employing positive environmental techniques including cogeneration, waste-coal usage, clean coal technologies, remining and land reclamation.

Cogeneration is a technology that has experienced resurgence beginning in the 1980’s. Cogeneration plants (cogens) use coal as a fuel for both heat and power. In a traditional coal-fired plant, steam produced by the combustion process turns the turbine, which drives a generator to produce electricity. In a cogen plant, as the steam turns the turbine, it also provides direct heat to another user. Among the beneficiaries of the cogens’ heat are prisons, fish farms and greenhouses.

Waste-coal-fired power plants utilize new technology to burn coal refuse that, due to its low carbon content, could not have been used in traditional coal-fired plants. The coal is gathered from culm banks, also known as gob piles; some of these toxic mounds are over 200 feet high. In order to combust the waste, plants use a circulating fluidized bed boiler, a boiler of moving air.

Clean coal technologies (CCTs), encouraged by a government and industry initiative that began in 1984, help to reduce the emission of sulfur dioxide, nitrogen oxide, mercury, a host of other elements, and to a lesser extent, carbon dioxide. Sulfur dioxide and nitrogen oxide contribute to the formation of “acid rain," which can damage plant and animal life. Mercury is a health threat to people when they eat fish contaminated by polluted water. According to many scientists, carbon dioxide mixes with oxygen to cause global warming, a situation in which the earth’s heat is trapped in the atmosphere, creating the "greenhouse effect.” These scientists believe that, unabated, global warming could lead to worldwide catastrophic weather changes.

Several modifications have been made to improve sulfur emissions from coal-fired power plants. First, washing the coal before it is sent to a power plant removes some of the impurities. At some power plants, crushed coal is mixed and burned with limestone in a fluidized bed boiler. This process allows the limestone to combine with sulfur particles to form a compound, which is then extracted.

Another method reduces sulfur dioxide gases after the coal is burned. This process takes place in "scrubbers," or flue gas desulfurization units. A combination of water and crushed limestone is sprayed into the coal gases as they rise in the smokestacks. The limestone absorbs much of the sulfur dioxide before the gases are expelled into the environment. To decrease the emission of nitrogen oxide, coal is burned at lower temperatures. Together, these practices remove more than 95% of the pollutants caused by sulfur and nitrogen.

Mercury is removed by calcium-based absorbents (sorbents). Other methods are being developed to further reduce mercury emissions.

Coal gasification, one of the most advanced clean coal technologies, uses a coal conversionprocess. Coal,combined with steam and oxygen, is heated at high temperatures, changing itinto synthesis gas. By using this process, 99% of the sulfur content can be removed from the coal. Carbon monoxide and hydrogen gases can be collected to make useful products. Methanol fuel, produced in coal-gasification plants, can be used as a fuel for vehicles. Many such plants use an integrated gasification combined-cycle process (IGCC) to further reduce pollution and waste. Hot coal gases are used to run a gas turbine for producing electricity, and theresidual heat is used to boil water for a traditional steam generator and to produce electricity.

A number of other CCTs exist, some of which, while not in widespread use at this time, are being broadly researched. One of them, coal liquefaction is a conversion technique in which coal is changed into a liquid. Another, carbon sequestration, is a process that significantly reduces the amount of carbon dioxide emissions, thus, minimizing the amount of greenhouse gases in the atmosphere. Currently, due to economic and technological constraints, carbon dioxide emissions continue to cause significant problems in many traditional and waste-coal-fired plants.

Even as new CCTs are being studied, efforts are being made to remine abandoned sites, and to reclaim land and water damaged by the coal industry. Remining operations involve extracting the remaining coal from previously mined areas. Land reclamation programs funded by government sources, coal operators, and private organizations are many and varied. In one example, waste-coal processing facilities use the alkaline ash, residue from the combustion process, to fill surface mine and underground mine sites. After surface mines are filled, the land is restored. Out of the ashes, meadows, forests, recreational sites, and areas for development are rising.

In other examples, water pollution issues are being addressed. In an attempt to neutralize acid mine drainage into nearby water sources, the water is being treated with limestone in order to increase its alkalinity. Also, runoff holding areas are being built for the acid waters so that smaller amounts move into nearby streams. In other cases, lands are being regraded to approximate their original routes so that dried-up streams, cut off from their sources by coal mines, can flow once again.