Environmental Impact of Geothermal Energy





Geothermal energy, by textbook definition, is reliable energy that is generated from the Earth. It has long been a statute-recognised resource that is not only renewable, but also sustainable. In the United States, the first geothermal power plant was established at The Geysers in the state of California back in 1960 where it has continued to provide huge amounts of energy to this day. The United States is one of the world’s largest producers of electricity sourced from geothermal facilities and it averages about 15 billion kilowatt hours of power every year. Their output of power is almost equal to burning 6 million short tons of coal or 25 million barrels of oil.

Air Emissions from Geothermal Plants and Facilities

Nesjavellir Geothermal Power Plant in Þingvellir, Iceland releases pollution free steam.

Nesjavellir Geothermal Power Plant in Þingvellir, Iceland releases pollution free steam.

Technically, because geothermal power plants do not make use of fuel through the act of burning like fossil fuel plants do, these plants do not produce air emissions. The fumes, which look like smoke and can be observed from the atmosphere surrounding these plants, are most likely to be water vapor. However, there are four known important pollutants that are emitted by these geothermal plants. These pollutants include nitrogen oxide (NOx), sulfur dioxide (SO2), particulate matter (PM) and carbon dioxide (CO2). Of the four substances, carbon dioxide (CO2) is released into the atmosphere at the highest concentration with levels ranging from 0-88.8 lb/MW.

Laboratory and onsite studies have shown that geothermal plants do not emit sulfur dioxide directly into the atmosphere, unlike coal plants. What happens instead is that hydrogen sulfide is released as a gas into the environment, which is then ultimately converted into sulfur dioxide and sulphuric acid. Thus, any substantial amount of the substance sulfur dioxide that is found in the surrounding atmosphere of geothermal plants is simply a derivative of hydrogen sulfide.

Apart from the four harmful chemicals mentioned it has also been determined that mercury is present in areas where geothermal power plants are in operation. In these cases, equipment is specifically designed to reduce the level of the substance in its surrounding environment and to effectively wipe out the emission levels by as much as 90% or more.

Health Effects of the Geothermal Emissions

There are several negative health effects that nitrogen oxide (NOx), sulfur dioxide (SO2), particulate matter (PM) and carbon dioxide (CO2) can have on the general population. Nitrogen oxide has been known to cause varied symptoms of lung irritations such as coughing, wheezing and persistent colds. Nitrogen oxide also causes smog. Also, the quality of the water contaminated by this substance is decreased making it not very safe for humans, especially school aged children. Sulfur dioxide causes more severe effects that lead to wheezing, tightness of the chest, serious respiratory illnesses, and long lasting damage to the ecosystem. Particulate matter (PM) has been known aggravate the symptoms of asthma, and cause bronchitis and certain systemic cancers such as lung cancer. It can lead to atmospheric deposition of the environment and impaired visibility for all types of aircrafts. Global warming is consequently caused by too much carbon dioxide (CO2) in the atmosphere.

Community Issues for Geothermal Power

Apart from the harmful health risks caused by geothermal plants and facilities there are numerous environmental issues that are of concern. For one, geothermal power plants have been observed to utilize around 5 gallons of freshwater for every megawatt hour of energy they produce, while those that are cooled via binary methods do not make use of any water at all. On the other hand, natural gas facilities use about 361 gallons of freshwater per megawatt hour of energy generated, which is a considerable difference when compared to geothermal plants.

Diagram of the Enhanced Geothermal System involving reinjection of used water. Image by Siemens Pressebild License: CC BY-SA 3.0

Diagram of the Enhanced Geothermal System involving reinjection of used water. Image by Siemens Pressebild License: CC BY-SA 3.0 - 1. Reservoir 2. Pump House 3. Heat exchanger 4. Turbine Hall 5. Production Well 6. Injection Well 7. Hot water 8. Porous Sediments 9. Observation Well 10. Bedrock

Generally geothermal fluids that are utilized to produce electricity are injected back into scientifically engineered reservoirs with the use of water wells that are encased in thick coverings. These coverings are installed for the sole purpose of preventing cross contamination between salt water and ground water sources. Ideally, these waters are not supposed to be merged into waterways located on the surface. This method of enclosing the water decreases the occurrence of water contamination and elevates the resiliency of geothermal reservoirs. This provides a more efficient means of producing sustainable energy from geothermal resources. In the United States, this type of water injection technology has been proven to be very effective.

It has been proposed that geothermal plants and facilities be designed in such a way that they do not provide too much of a visual, environmental, and recreational hindrance to the community. Considerable efforts have been made to ensure that geothermal plants are able to be incorporated into areas where recreational activities like hunting, skiing and even farming are being conducted. A geothermal plant utilizes approximately 404 square meters of land per gigawatt hour whereas a coal plant can take up as much as 3632 square meters per gigawatt hour produced.

Another observable phenomenon which is a cause for concern with geothermal plants is gradual downward sinking of land. This is commonly linked to the decline of less efficiently built geothermal reservoirs. Earthquakes are usually known as a natural occurrence and therefore unavoidable in most areas of the globe but geothermal injection methods and production activities have been blamed or associated with low-magnitude earthquakes and micro earthquakes. Typically, these quakes go undetected by the population since their intensities are usually very low. Nevertheless these events are being monitored carefully by geothermal companies in an effort to provide solid reassurances to the government and the community that host their facilities and power plants.

The impact of geothermal plants on the vegetation and wildlife of its surrounding regions have been carefully observed and documented over the years. Typically, before any new construction for geothermal facilities is done an extensive and independent review of the environmental conditions of the area will take place for a period of no less than six months up to a year. This is required in order to provide an in-depth examination of the area in case there are any issues between the proposed facility and the community. Apart from this, potential effects of geothermal activities on the flora and fauna of the region may be predicted after the review, thereby allowing the facilities to implement proper safety measures that will counteract harmful effects and possibly eliminate them.

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