Emissions and pollution are a key concern with traditional power sources. The coal-fired plants that dominate U.S. energy production also produce more emissions than any other energy source. Emissions are measured in pounds of emissions per megawatt-hour of energy produced. Coal generates 2,249 pounds of carbon dioxide, 13 pounds of sulfur dioxide and 6 pounds of nitrogen oxides for every megawatt-hour of energy generated. Natural gas the second most common source of energy in the U.S. fares better with respect to emissions, producing 1,135 pounds of carbon dioxide, 0.1 pounds of sulfur dioxide and 1.7 pounds of nitrogen oxides per megawatt-hour.
Solar, wind and geothermal power sources produce no emissions. Biomass produces nitrogen oxides and small amounts of sulfur dioxide. The amount of carbon dioxide produced does not exceed that of the Earth’s normal carbon cycle and is considered negligible.
The most common forms of traditional energy production are coal, natural gas and nuclear, all utilize water during mining processes and for cooling during combustion. The U.S. Environmental Protection Agency states that water removal for traditional energy use can damage wildlife populations of rivers and lakes. Burning biomass requires a supply of water and has an impact similar to traditional energy sources. Solar, wind and geothermal systems require little or no water and often reuse water supplies to minimize the impact.
Coal, natural gas and nuclear power all add pollutants to water that, if discharged into a lake or stream, can negatively impact water quality and harm wildlife. Energy generation from biomass presents similar concerns. Drilling geothermal wells can cause groundwater contamination if proper management practices are not observed. Wind and solar energy systems do not result in water pollution. Coal produces a solid waste called ash in addition to the pollution created during the mining process. Nuclear energy is another traditional system that results in large amounts of solid waste, which can take thousands of years to diminish. Natural gas produces no solid wastes. Biomass also produces ash, although the ash contains few hazardous materials. Solar cell manufacturer generates small amounts of hazardous materials, but they generate none during use. Wind and geothermal systems generate no solid waste that can act as a potential pollutant.
However, renewable sources such as wind, solar, geothermal, biomass, and hydropower also have environmental impacts, some of which are significant. The exact type and intensity of environmental impacts vary depending on the specific technology used, the geographic location, and a number of other factors. By understanding the current and potential environmental issues associated with each renewable energy source, we can take steps to effectively avoid or minimize these impacts as they become a larger portion of our electric supply.
Harnessing power from the wind is one of the cleanest and most sustainable ways to generate electricity as it produces no toxic pollution or global warming emissions. The wind is also abundant, inexhaustible, and affordable, which makes it a viable and large-scale alternative to fossil fuels. Despite its vast potential, there are a variety of environmental impacts associated with wind power generation that should be recognized and mitigated.
Like wind power, the sun provides a tremendous resource for generating clean and sustainable electricity. The environmental impacts associated with solar power can include land use and habitat loss, water use, and the use of hazardous materials in manufacturing, though the types of impacts vary greatly depending on the scale of the system and the technology used—photovoltaic (PV) solar cells or concentrating solar thermal plants (CSP) .
The most widely developed type of geothermal power plant (known as hydrothermal plants) is located near geologic “hot spots” where hot molten rock is close to the earth’s crust and produces hot water. In other regions enhanced geothermal systems (or hot dry rock geothermal), which involve drilling into the earth’s surface to reach deeper geothermal resources, can allow broader access to geothermal energy. Geothermal plants also differ in terms of the technology they use to convert the resource to electricity (direct steam, flash, or binary) and the type of cooling technology they use (water-cooled and air-cooled). Environmental impacts differ depending on the conversion and cooling technology used.
Biomass power plants share some similarities with fossil fuel power plants: both involve the combustion of a feedstock to generate electricity. Thus, biomass plants raise similar, but not identical, concerns about air emissions and water use as fossil fuel plants. However, the feedstock of biomass plants can be sustainably produced, while fossil fuels are non-renewable. Sources of biomass resources for producing electricity are diverse; including energy crops (like switchgrass), agricultural waste, manure, forest products, and waste, and urban waste. Both the type of feedstock and the manner in which it is developed and harvested significantly affect land use and life-cycle global warming emissions impacts of producing power from biomass.
Hydrokinetic energy, which includes wave and tidal power, encompasses an array of energy technologies, many of which still in the experimental stages or in the early stages of deployment. While actual impacts of large-scale operations have not been observed, a range of potential impacts can be projected.