Carbon dioxide emissions from the combustion of fossil fuels are directly linked to global warming and climate change. In 2010, the Carbon-dioxide emission was about 81.6 percent according International Energy Agency, and the emission was primarily due to the energy production and consumption. By 2020, the amount of Carbon emission will increase to 43.2 billion metric tons. It becomes necessary that we move towards relatively cleaner forms of energy. One such examples, is the Geothermal energy, which involves drilling into the earth’s surface to gain access to the heat from the hot molten rocks. Various technologies drive a geothermal plant. In terms of the techniques they use to convert resources to electricity, they can be categorized into-direct steam, flash and binary. Based on the variations in the cooling techniques, there are two types of geothermal plants-water cooled and air cooled. Each of these has different impacts on the environment.
Geothermal energy has a major influence on the quality of water. For the purpose of cooling and also reinjection, water is used. In the developed countries like the United States advanced wet recirculating technology is used along with the cooling towers. On an average a geothermal plant uses about 1700-4000 gallons of water, for every megawatt hour. These plants use geothermal fluids rather than fresh water, which reduce water wastage. Additionally geothermal plants reinject the water into the reservoir, after usage which prevents the subsidence of the land and its contamination. It is necessary that the amount of water in the reservoir in kept at constant levels, which would mean that at times water from outside would be required, but fresh water resources would not be required for this purpose, like ,most geothermal plants in California use wastewater that is treated to maintain the reservoir water levels.
The percentage emissions by geothermal plants depend on the type, whether it is open loop type or closed loop type. In closed loop systems the emissions produced during the plant operations are not released into the atmosphere, instead their temperatures are brought down and are administered back into the ground. In contrast to this, the open loop systems release Carbon dioxide, Ammonia, Methane, Boron and Hydrogen Sulphide. When the Sulphides are in contact with the atmospheric air, they get converted into Sulphur dioxide, which tends to cause acid rains. There is also a risk of Mercury emission in small percentage with a geothermal plant operations, but with efficient filter technology these can be brought down by a large extent.
The impact of geothermal energy on land varies with the type. The largest plant in the world named “The Geysers”, in California has a capacity of 1517MW and occupies an area of 13 acres per MW energy generated. Few geothermal plants increase risk of earthquakes, like with Enhanced geothermal plants, fracturing of rocks occurs with water pumped with extreme pressures. It thus becomes mandatory to properly select sites for setting up a geothermal plant. Certain amount of distance has to be maintained from any major fault lines, along with regular maintenance of the plant and the sites.
If a life cycle of Global warming emissions has to be considered for Geothermal, then for open loop type 10 percent emission of Carbon dioxide are common, while with enhanced geothermal 0.6 -2 pounds per kilowatt-hour, Carbon impurities are generated. If a conclusion has to be drawn, then geothermal energy is a cleaner alternative to fossils fuels