ENVIRONMENTAL FACTORS

There are several environmental factors related to geothermal energy projects that can potentially affect their public acceptance. For example:

ATMOSPHERE IMPACTS

• Air pollution: Release of gases in the atmosphere is a phenomenon called degassing and can occur during the geothermal development if the geothermal fluids extracted from the reservoir up to the surface have a gas content.

WATER IMPACTS

• Water usage: Geothermal power plants can require a considerable amount of water throughout the various phases of the asset life.
• Water pollution: Contaminants relevant to water pollution are similar to those of atmospheric pollution (H₂S, Bo, NH³, Hg, As, Pb, Cd, Fe, Zn), with a diverse composition of high-temperature geothermal fluids, depending on the geological setting of the system.

LAND IMPACTS

• Land usage: Land used by geothermal plants includes the area occupied by the drilling pads, the well-heads, the geothermal plant facilities, the geothermal fluid transport pipelines, and the electricity transmission lines.
• Induced seismicity: Geothermal activities are concentrated into natural seismic active zones. Geothermal energy production is related to extensive extraction or circulation of geofluids, and manipulation of the shallow and deep ground, which can lead to environmental effects, such as induced seismicity (Bayer et al. 2013[1]; Evans et al. 2012[2]).
• Land subsidence & deformation: Land subsidence can occur when fluid and steam from geothermal reservoirs is removed, causing the sinking of the geothermal reservoir and potential damages to the built environment in the surrounding area (Cook et al. 2017[3]).
• Solid waste: Typical waste of low temperature geothermal systems include cuttings and residues produced during drilling, steel, copper, scrap metals, excavated soil, as well as plastics from packaging, construction material for buildings and road construction (Manzella et al. 2019[4]). In high temperature geothermal systems, scale from cooling water, scale from maintenance, toxic metals and hazardous waste from geothermal fluids in pipes, vessels filters and other tools can also be found (Vetter 1983[5]).

NOISE, VISUAL POLLUTION, AND RADIOACTIVITY

• Noise pollution: Throughout the life of a geothermal energy system, noise can be created during the well testing, drilling and building activities, operation and decommissioning.
• Visual pollution: Surface disturbances of geothermal plants are associated with landscape effects, land occupation, as well as disturbances associated with road traffic and dust emissions (Manzella and Al. 2019[6]).
• Radioactivity: As the geothermal fluid flows through a fractured granite, naturally enriched in radionuclides such as uranium and thorium, a small fraction is leached by the fluid and can reach the surface. These factors might be related of both deep and shallow geothermal systems, throughout the lifecycle of the project, and each factor has its criticality level in terms of its impact on public acceptance.