Detailed Recommendations for Geothermal Energy

Infrastructure and General Siting Concerns

Typically several wells are drilled to support a geothermal power plant. This points out a potentially important distinction in the infrastructure of geothermal energy production versus some other energy sources: not only is the "fuel" produced on public lands, but in contrast to oil, gas, coal, or uranium, the power plant must be located adjacent to the wells, which as indicated above, may well be on public lands. Photographs of geothermal energy plants appearing on websites indicate they are major industrial facilities. In addition, roads and power lines to support the wells and power plant must be constructed.

Consequently, the environmental impacts of geothermal energy development, especially on public lands, need to be carefully regulated. Agencies should ensure incompatible uses do not occur. Other important public resources, values and assets should be fully considered and protected before geothermal energy development is permitted on public lands. On private lands it is important that geothermal energy development complies with local planning and zoning laws, and it should be compatible with any special land use designations on adjacent lands, such as parks, recreation areas, or wildlife management areas.

Fortunately geothermal power plants themselves require relatively little land compared to fossil fuel and nuclear power plants:

"Ronald DiPippo, a geothermal energy researcher at the University of Massachusetts, has calculated that a typical geothermal power plant requires about 3 acres for every 10 Megawatts of generating capacity, compared to about 100 acres for a coal-fired plant, including the land mined to fuel the plant during a thirty-year operating life." (Richard Golob & Eric Brus, The Almanac of Renewable Energy, p. 78).Moreover, directional drilling can be utilized, and several wells can be drilled from one pad, which minimizes the need for access roads.

With careful attention to siting, Defenders believes geothermal energy can often be developed in an environmentally acceptable way; however, there will be places where geothermal energy development should not be permitted. For example, geothermal energy development adjacent to Yellowstone National Park could adversely affect the park’s world-renowned geothermal features. In some areas, development of geothermal energy could affect unique species of wildlife adapted to thermal pools, so again geothermal energy development could be inappropriate in these areas.

Geothermal Leasing And Siting Concerns On Public Lands

Development of geothermal energy on public lands is done by leasing using a process similar to that used for leasable minerals (oil, gas, and others). Pursuant to the Geothermal Steam Act of 1970 (30 U.S.C. 1001 et seq), BLM can issue leases on lands administered by the Department of the Interior or the Department of Agriculture (with its concurrence). However, National Parks, National Recreation Areas, National Wildlife Refuges, wilderness areas, and wilderness study areas are not available for leasing. Moreover, BLM regulations provide that leasing will not be done where the lease would cause unnecessary or undue degradation to public lands and resources. And in what can only be characterized as confusing provisions, BLM can allow leasing if it is determined that activities under a lease "might adversely affect" a significant geothermal feature in a National Park so long as protective stipulations are attached to the lease; however, if geothermal operations are "reasonably likely to result in a significant adverse effect" on significant geothermal features in a National Park, leasing is not to occur.

Development of geothermal resources on public lands involves many of the infrastructure requirements of oil and natural gas development (roads, well pads, power lines, etc.). And as mentioned, unlike oil, natural gas, and coal, geothermal steam plants need to be located immediately adjacent to the wells, so these industrial facilities need to be built on public land as well. Consequently, geothermal energy development could create many of the impacts that characterize oil and gas development (habitat fragmentation, etc.). BLM regulations make numerous provisions to prevent negative impacts on other resources due to geothermal energy development, and it is imperative that these provisions be enforced. Moreover, as discussed above, in some instances countervailing resource values (for example, critical habitat for endangered species) may make leasing inappropriate even with protective stipulations or other efforts to protect the environment.

Air, Water and Solid Waste Pollution Concerns With Geothermal Energy Development

An important concern relative to the potential environmental impact of geothermal energy development relates to water. Environmental impacts can result from the hot waters and steam used to generate electricity, which often contain many dissolved toxic compounds (see below). Groundwater contamination is an important concern. Generally groundwater pollution can be prevented if the wastewater is disposed of by re-injection, and this approach is usually employed because the water can then potentially be reused once it has been reheated by the earth. It is critical that waste waters be re-injected in a way that ensures groundwater aquifiers are not polluted, including ensuring well casings do not have leaks.

In addition to the potential for contamination of groundwater (or surface waters if re-injection is not employed), a large amount of water is needed for cooling and other purposes in most geothermal plants, which can create problems, especially in arid areas. Heated waters should not be disposed of into naturally cooler streams due to the negative impacts on aquatic ecosystems, and withdrawals of cooling water should not be allowed to de-water streams or otherwise disrupt the ecological functions in aquatic environments. There is also the potential for conflict with other water users for water resources where water is not plentiful, and these concerns need to be addressed.

The amount of air pollution and solid waste resulting from geothermal energy production depends on the type of system employed. Closed-loop geothermal systems have the least impact, because gases and fluids are fully contained throughout the production cycle and are injected back into the ground after their heat energy is gleaned. Again, it is important that the injection be well below fresh water aquifers. Re-injection may also help prevent land from sinking or settling, although this problem has so far only been detected at one site located in New Zealand. Closed-loop systems are more expensive than conventional open-loop systems, but it should be noted that reduced scrubber and solid waste disposal costs could present an economic advantage.

Open-loop systems can generate large amounts of solid waste and noxious fumes. Steam vented at the surface can contain hydrogen sulfide, causing a "rotten-egg" smell, as well as ammonia, methane, nitrogen, hydrogen, and carbon dioxide. Notably, the carbon dioxide emitted at geothermal plants is about 5 percent of that emitted by coal- or oil-fired power plants per kilowatt-hour of energy generated. Geothermal plants emit no nitrogen oxides and low amounts of sulfur dioxide. Scrubbers can reduce air emissions but they produce a sludge that is high in sulfur and the heavy metal vanadium. When steam is condensed, additional sludge is created, which can contain silica compounds, chlorides, arsenic, mercury, nickel, and other heavy metals. This sludge can create solid waste disposal problems that must be dealt with in an environmentally acceptable way. One costly method involves drying the sludge and shipping it to hazardous waste sites. Current research is looking into the possibility of treating the waste with microbes that would recover commercially valuable metals, and render the waste nontoxic. Another approach is to re-dissolve solids so that they can be reinjected.