Chapter 14 - Energy Sources and Air Pollution - PDF

## Energy Sources and Air Pollution ### Learning Objectives - Outline the history of human energy use - Understand the challenges to continued reliance on fossil energy - Outline environmental impacts of energy use - Evaluate the different energy sources based on their environmental impact - List...

## Energy Sources and Air Pollution ### Learning Objectives - Outline the history of human energy use - Understand the challenges to continued reliance on fossil energy - Outline environmental impacts of energy use - Evaluate the different energy sources based on their environmental impact - List common air pollutants and their sources - Explain the impact of human activity on the ozone layer - Describe how acid rain forms and causes environmental damage ### Energy Sources Energy sources are the natural resources that provide the power to light, heat and cool buildings, manufacture products, and power transportation systems. - The earth’s core provides **geothermal energy**. - The gravitational pull of moon and sun create **tides**. - The sun emits light, creating **wind**, powering the **hydrologic cycle**, and enabling **photosynthesis**. - Plants, algae, and cyanobacteria utilize solar energy to grow and create **biomass** that can be burned and used for **biofuels**, like wood, biodiesel, bioethanol. - Over millions of years, biomass can create **fossil fuels** through geologic processes. Each of these types of energy can be defined as **renewable** or **non-renewable**. Renewable energy sources can be replenished within human lifespans, like solar, wind, and biomass energy. Non-renewable energy is finite and cannot be replenished within a human timescale, such as nuclear energy and fossil fuels. All energy sources have environmental and health costs, and the distribution of energy is not equally distributed among all nations. ### Non-Renewable Energy Sources Fossil fuels come from the organic matter of plants, algae, and cyanobacteria that was buried, heated, and compressed under high pressure over millions of years. The process transformed the biomass of those organisms into the three types of fossil fuels: oil, coal, and natural gas. #### Petroleum (oil) Petroleum is used for 37% of the world’s energy consumption and 36.35% of the United States energy consumption. It is generally thought that peak oil will be reached by the middle of the 21st Century. The world reserves are 1.3 trillion barrels, or 45 years left at the current level of production. Oil is usually found one to two miles below the Earth’s surface. Once oil is found and extracted it must be refined, which separates and prepares the mix of crude oil into the different types for gas, diesel, tar, and asphalt. Oil refining is one of the top sources of air pollution in the United States for volatile organic hydrocarbons and toxic emissions, and the single largest source of carcinogenic benzene. There are other domestic sources of oil that are being researched as potential conventional resources such as **tar sands** (deposits of moist sand and clay with 1-2 percent bitumen) and **oil shale** (sedimentary rock filled with organic matter that can be processed to produce liquid petroleum). However, the net energy values are low and they are expensive to extract and process. Both of these resources have severe environmental impacts due to strip mining, carbon dioxide, methane and other air pollutants similar to other fossil fuels. #### Coal Coal is another fossil fuel. Due to its relatively low cost and abundance, coal is used to generate about 15.6% of the electricity consumed in the United States. Coal production doubled in the United States between 1950 and 2010. Current world reserves are estimated at 826,000 million metric tons (182 million pounds), with nearly 30% of that in the United States. Coal is plentiful and inexpensive. It produces a multitude of negative externalities that the market cost does not truly capture. Coal emits sulfur dioxide, nitrogen oxide, and mercury, which have been linked to acid rain, smog, and health issues. Burning coal causes higher emissions of carbon dioxide per unit of energy than burning oil or natural gas. Coal accounted for 35% of the total United States emissions of carbon dioxide released into the Earth’s atmosphere in 2010. Ash generated from combustion contributes to water contamination. Some coal mining has a negative impact on ecosystems and water quality, and alters landscapes and scenic views. There are also significant health effects and risks to coal miners and those living in the vicinity of coal mines. Traditional underground mining has a high risk to mine workers due to the risk of entrapment or death. - Twenty-nine miners died on April 6, 2010 in an explosion at the Upper Big Branch coal mine in West Virginia. - In May 2011, three people died and 11 were trapped in a coalmine in Mexico for several days. Coal miners are also at risk of getting **black lung disease** (pneumoconiosis), caused by the inhalation of coal dust over a long period of time. It causes coughing and shortness of breath and is responsible for tens of thousands of deaths per year. **Mountaintop mining (MTM)** is a surface mining practice involving the removal of mountaintops to expose coal seams, and disposing of the associated mining waste in adjacent valleys. This form of mining is very damaging to the environment because it destroys the existing habitat. #### Natural Gas Natural gas is a fossil fuel consisting primarily of methane (CH4). Natural gas leaks are the source of about 25% of total U.S. methane emissions, which translates to three percent of total U.S. greenhouse gas emissions. Natural gas is often considered a preferred fossil fuel compared to oil or coal when considering its environmental impacts. It produces less carbon dioxide, nitrogen oxides, and sulfur dioxide when burned. However, there is still a great deal of environmental damage associated with natural gas production. Most natural gas in the United States is now extracted from deep layers of rocks known as shale. Extraction of shale gas is more problematic than traditional sources due to a process known as **hydraulic fracturing**, or **fracking**. The technique uses high-pressure fluids to fracture the normally hard shale deposits and release gas and oil trapped inside the rock. The considerable use of water can affect the availability of water for other uses. The fluid contains potentially hazardous chemicals such as hydrochloric acid, glutaraldehyde, petroleum distillate, and ethylene glycol. ### Renewable Energy Sources #### Hydropower Hydropower provides about 25% of the United States' renewable energy consumption. Hydropower dams and the reservoirs they create can have environmental impacts. For example, the migration of fish can be obstructed by dams. Reservoirs and operation of dams can also affect aquatic habitats due to changes in water temperatures, water depth, chemistry, flow characteristics, and sediment loads. #### Liquid Biofuels Bioethanol and biodiesel are two types of liquid biofuels manufactured from plants to replace fossil fuels. Bioethanol can be easily fermented from sugar cane juice, as is done in Brazil, and can also be fermented from broken down corn starch, as is mainly done in the United States. The economic and social effects of growing plants for fuels needs to be considered, as the land, fertilizers, and energy used to grow biofuel crops could be used to grow food crops instead. The competition of land for fuel vs. food can increase the price of food, which has a negative effect on society. It could also decrease the food supply increasing malnutrition and starvation globally. #### Geothermal Energy Five percent of the United States' renewable energy comes from geothermal energy. Geothermal systems utilize a heat-exchange system that runs in the subsurface about 20 feet below the surface where the ground is at a constant temperature. The system uses the earth as a heat source (in the winter) or a heat sink (in the summer). Geothermal power plants do not burn fuel to generate electricity so their emission levels are very low. They release less than 1% of the carbon dioxide emissions of a fossil fuel plant. After the steam and water from a geothermal reservoir have been used, they are injected back into the earth. #### Solar Energy Solar power converts the energy of light into electrical energy and has minimal impact on the environment, depending on where it is placed. Solar power generation releases no carbon emissions or other air pollutants, but the manufacturing of photovoltaic (PV) cells generates some hazardous waste from the chemicals and solvents used in processing. Often solar arrays are placed on roofs of buildings or over parking lots or integrated into construction in other ways. However, large systems may be placed on land and particularly in deserts where those fragile ecosystems could be damaged if care is not taken. #### Wind Energy Wind energy is a renewable energy source that is clean and has very few environmental challenges. Wind turbines do not release emissions that pollute the air or water (with rare exceptions), and they do not require water for cooling. Because a wind turbine has a small physical footprint relative to the amount of electricity it produces, many wind farms are located on crop and pasture land. They contribute to economic sustainability by providing extra income to farmers and ranchers. Offshore wind turbines on lakes or the ocean may have smaller environmental impacts than turbines on land. Wind turbines do have a few environmental challenges: - **Aesthetic Concerns**: Some people do not like how wind turbines look on the landscape. - **Noise**: Some people do not like the sound that wind turbine blades make. - **Bird and Bat Deaths**: Turbines have been found to cause bird and bat deaths, particularly if they are located along their migratory path. - **Construction Impacts**: There are some small impacts from the construction of wind projects or farms, such as the construction of service roads, the production of the turbines themselves, and the concrete for the foundations. ### Air Pollution Air pollution can manifest in many forms, generally as gases and particulate contaminants present in the earth’s atmosphere. Chemicals discharged into the air that have a direct impact on the environment are called primary pollutants. These combine with other chemicals in the atmosphere to form secondary pollutants. **Six of the most common air pollutants are considered to be harmful to human health.** ###### **Carbon monoxide (CO)** is a colorless, odorless, and toxic gas that is produced by the incomplete combustion of fossil fuels. It reduces oxygen delivery to the body's organs by binding to hemoglobin in the blood. It can be found in vehicle exhaust, industrial emissions, and smoke from fires. ###### **Sulfur dioxide (SO2)** is a colorless gas with a pungent odor that is produced primarily by the burning of sulfur-containing fossil fuels. It is the main cause of acid rain. It can be found in emissions from power plants, industrial facilities, and vehicles. ###### **Nitrogen oxides (NOx)** are a group of highly reactive gases that include compound such as nitrogen dioxide (NO2), and nitrous oxide (N2O). NOx are a major contributor to smog and acid rain. They are produced by the combustion of fossil fuels, including gasoline, diesel, and natural gas. ###### **Volatile organic compounds (VOCs)** are a large group of man-made and natural chemicals that contribute to smog formation. They come from a variety of sources, including vehicle exhaust, industrial emissions, and solvents from paints, adhesives, and cleaners. ###### **Particulate matter (PM)** is a mixture of solid particles and liquid droplets that are suspended in the air. It is categorized by size including PM10 and PM2.5. The smaller the particulate, the more readily it can travel into the lungs. They are produced by a variety of sources, including power plants, industrial processes, construction activities, and vehicle exhaust. ###### **Ozone (O3)** is a colorless gas with a pungent odor that is produced when nitrogen oxides and volatile organic compounds react in the presence of sunlight. It is the primary component of **smog** and can cause respiratory problems, chest pain, and coughing, and it can also damage crops and other vegetation. ###### **Acid rain** refers to precipitation that is more acidic than normal, with a pH of less than 5.0. The chemicals that cause acid rain come from both natural sources such as volcanoes, decaying vegetation, and human-made sources, primarily emissions of sulfur dioxide (SO₂) and nitrogen oxides (NOx) resulting from fossil fuel combustion. ### Ozone Depletion - The ozone is a chemical compound of oxygen that naturally exists in the stratosphere. It acts as a shield, absorbing harmful ultraviolet rays from the sun to protect life on Earth. - The release of chlorofluorocarbons (CFCs), into the atmosphere caused a thinning of the ozone layer in the stratosphere, especially over Antarctica, called the “ozone hole.” ### Acid Rain Acid rain forms when sulfur dioxide and/or nitrogen oxides are released into the atmosphere and combine with water droplets to form acids. - **The ecological effects of acid rain are most clearly seen in aquatic environments**, such as streams, lakes, and marshes. The primary acidic compounds are sulfuric and nitric acids, and aluminum (which is highly toxic to many aquatic organisms). - **Acid rain also causes slower growth, injury, or death of forests.** - **Acid rain and the dry deposition of acidic particles contribute to the corrosion of metals**, and paint and stone. ### The Clean Air Act Government regulation has been one of the most effective methods of reducing air pollution. The Clean Air Act was passed in the United States in 1970 to regulate air pollutants such as lead, particulate matter, and carbon monoxide. The law was amended in 1990 to control acid rain-causing sulfur dioxide and nitrogen oxides. Due to the implementation of this law and further regulation, emissions of several major air pollutants have fallen since 1990 and are currently below levels that are considered unsafe. The EPA estimates that this reduction in air pollution prevents over 200,000 premature deaths and about 17 million lost work days per year. It has also found that the economic benefits of the Clean Air Act have been more than 30 times greater than the costs of implementing it.