One of the best sources of green technology information and their impact on climate change is the National Resources Defense Council (NRDC). According to the NRDC “geothermal energy, which taps into reservoirs of steam and hot water beneath the earth's surface, is among the least explored sources of renewable energy in the United States. In 2005, geothermal energy produced just 0.36 percent of the electricity used in this country, about 3,000 megawatts of energy.” The potential for geothermal development as an energy source could provide as much as 100,000 megawatts of power by 2025 according to the National Renewable Energy Laboratory.
So what are the drawbacks to utilizing our vast reservoirs of geothermal energy?
Geothermal power works very much like the steam engines of old that most of us are familiar with. Heat up a boiler tank of water and the pressure built up will be released as energy that then by design can move mechanical parts to serve various tasks. But unlike steam engines utilizing bio-mass materials to create the heat for steam power, geothermal sources are stationary and the means to move the force of that energy to areas that need to be served will require a large investment up front. The return on this economic expense will be quickly gained but once these initial costs are sourced the environmental concerns that geothermal energy creates needs to be dealt with.
Most geothermal sources in America are in our Western States. They happen to reside in what are also some of our most beautiful and pristine habitats that are protected by law, like Yellowstone National Park and the Cascade Mountains. Extracting this source of energy from certain sensitive sites would not only draw public opposition but risks harming these protected areas permanently. Thus any compromise that governments and entrepreneurs create to develop geothermal power supplies in these areas must work through the delicate issues of preserving habitats centuries old and the rare species that dwell there.
Costs will be affected by plant site locations in order to avoid distracting from or damaging the ecosystems where efforts are made to gain the greatest access and benefit from geothermal reservoirs. Transmission lines will have to be planned to avoid similar ecological destruction as they carry this power source from the generator station to the distribution sources. Further environmental damage can also result from the type of extraction process used.
In the process of taking geothermal steam or hot water and converting it into electricity, some waste products will be created. How much and what kind depends on the method used. There is the more expensive “closed looped” system that contains pretty much all of the gases and fluids it extracts from a well and re-injects them after it removes the heat. Essentially nothing is lost.
“Open-loop systems, on the other hand, can generate large amounts of solid wastes as well as noxious fumes. Metals, minerals, and gases leach out into the geothermal steam or hot water as it passes through the rocks. The large amounts of chemicals released when geothermal fields are tapped for commercial production can be hazardous or objectionable to people living and working nearby.” (Cool Energy: Renewable Solutions to Environmental Problems, by Michael Brower, MIT Press, 1992)
To first time visitors at California’s The Geysers, the country’s largest geothermal development, the odor of “rotten eggs” will hit you almost instantly. This comes from the hydrogen sulfide (H2S) that comes with the steam vented near the surface, along with elements of ammonia, methane, and carbon dioxide. Though the CO2 that is emitted from these open-loop systems can make their way into the atmosphere they make up only 10% of the CO2 that are generated through the use of any coal-fired or oil-fired power plant.
Other waste issues that can occur are the result of “scrubbers”; a means to reduce air emissions. Watery sludge high in sulfur and vanadium, a toxic substance in high concentrations, can be produced through scrubbing and needs to be managed through a costly drying process that allows this toxic mix to be transported to licensed hazardous waste sites.
Clearly the safer method is the closed-loop system that recycles all waste products back to their source. Care must be taken however to inject this waste by-product “well below fresh water aquifers to make certain that there is no communication between the usable water and waste-water strata. Leaks in the well casing at shallow depths must also be prevented.” (Ibid)
Water conservation can be an issue also with developing geothermal sites. It requires tons of water for cooling and other purposes to operate a geothermal power plant. Limited resources of water in a given area could be the single biggest environmental concern when it comes to a decision of where geothermal wells can be dug.
Though faced with these environmental conflicts, geothermal energy is still environmentally much safer and cleaner than extracting coal and oil. It is not only a source of job creation but one where worker safety is more pronounced. It is an abundant resource and unlike solar and wind, it is a renewable source of energy that is constant. With careful and thoughtful planning the prospects for adding geothermal energy to the nation’s often-stretched electrical grid will put us that much closer to lowering our carbon footprint and ending our dependence on foreign oil.
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