Direct use and its possible environmental effects
In principle, the environmental impacts of direct use are in the same categories as with power generation. However, but the degree to which utilization affects the environment is proportional to its scale. As the various phases of direct utilization are on a much smaller scale and the heat/fluid production from the subsurface are considerably less than in power generation, the environmental effects of direct use are correspondingly smaller. Possible effects are listed i Table 3.
Table 3: Potential environmental impacts of direct use geothermal projects: probability and severity (from Lunis 1989)
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Environmental regulation, avoidance/remediation/mitigation measures
Although environmental legislation for geothermal development in various countries based on similar principles, their formulation and implementation can vary from country to country (Rybach 2003). There is a main similarity that the legal provisions extend during all development phases, from an environmental impact analysis in the planning and feasibility phases over construction and operation permits to the monitoring of production. Also there are specific regulations that limit the quantities of pollutants that may be emitted to the atmosphere or discharged to land and water. Some legislative sources from the USA, Philippines, New Zealand and Italy are given in Table 4.
Table 4: Examples for legislation relevant to geothermal development. From Brown (1995).
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For geothermal projects it is advisable to declare and assess for all development phases the possible environmental impacts (direct/indirect, short term/long term, reversible/irreversible, significant/negligible). As an example, Table 5 shows the environment compartments and aspects considered for the Deep Heat Mining project in Switzerland. In Switzerland, all geothermal installations > 5 MWt must turn in an environmental impact report.
Table 5: The environmental compartments and aspects investigated for an Environmental Impact Report (after Minder 2002).
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Most countries have developed or adopted criteria to protect their own environment. The criteria are usually designed to specifically protect native species or ecosystems. There aren key sets of criteria on which most others are at least partially based on:
• air quality;
• drinking water protection;
• aquatic life protection;
• stock watering and irrigation.
There are numerous ways and means to avoid or at least mitigate the environmental effects and impacts of geothermal activities.
Table 6: Potential impacts of large-scale geothermal development.
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Reference :
Rybach, L. (2003): Geothermal energy: sustainability and the environment. Geothermics
Tags: deep heat mining, Environmental effects, environmental impacts, geothermal development, geothermal projects