Environmental Impacts

WG 1- Environmental Impacts of Geothermal Energy Development

Operating Agent: GNS Science, New Zealand

Working Group Leader: Chris Bromley, GNS Science, New Zealand. Email: c.bromley@gns.cri.nz

Status: Ongoing

Participants: Australia, Iceland, Italy, Japan, New Zealand, Norway, Switzerland, United States

Description

Geothermal is a renewable energy source, has significant benefits relative to fossil fuels with respect to global carbon dioxide emissions, and accordingly has significant potential for reducing global warming effects. Its use is mostly environmentally benign. However, there are some local environmental problems associated with geothermal utilization.  To further the use of geothermal energy, it is important to identify possible adverse and beneficial environmental effects, and devise and adopt measures to avoid or minimize adverse impacts, while encouraging the benefits.

The goals of Working Group 1 are: to encourage the sustainable development of geothermal energy resources in an economic and environmentally responsible manner; to quantify and balance any adverse and beneficial impacts that geothermal energy development may have on the environment, and to identify ways of avoiding, remedying or mitigating adverse effects. Activites include five Tasks.

Task A- Impacts on Natural Features

Impacts of geothermal developments on natural geothermal features such as geysers,hot springs and fumaroles are documented.  Methods are devised to accurately monitor changes and to avoid or mitigate the adverse impacts of development on these geothermal features, which often have significant economic value for tourism and cultural value for indigenous peoples.

Task B- Discharge and Reinjection Problems

Better methods of overcoming adverse impacts of geothermal developments on aspects of the environment are developed.  These include the effects of gas emissions from geothermal power plants on air quality; the effects of toxic chemicals in waste fluid that may be discharged into the ground or into rivers; and the effects of ground subsidence resulting from pressure decline. Projects examine the problems associated with disposal of waste geothermal fluids and the effects of CO2, Hg and H2S gas emissions, along with mechanisms and mitigation options such as using injection to mitigate ground subsidence.

Task C- Methods of Impact Mitigation and Environmental Procedures

The objective of this task is to reduce the risks of adverse effects by developing an effective, standard, environmental analysis process.  By reducing the costs of environmental compliance, and stream-lining the process for project consenting, this will contribute to the responsible and timely deployment of future geothermal energy projects. Strategies that result in improved environmental outcomes from field management are identified and publicized. Successful mitigation schemes that provide developers and regulators with options for compensating unavoidable effects are also identified, documented and publicized.

Task E- Sustainable Utilization Strategies

Case histories of reservoir models of geothermal developments are studied to see what strategies have been successful. Additional modelling of long term reservoir behaviour is undertaken to select optimum future strategies given different recharge and resource size scenarios.  Different sustainable development scenarios are compared to determine relative environmental and economic benefits. Different conceptual and hypothetical reservoir model predictions are compared using long-term scenarios. Long-term reservoir behaviour, recharge factors, recovery times, and optimised cyclic or staged operation strategies are investigated.