Advances in Environmental Management of Geothermal Developments

Abstract

Over the past five years, advances have been made in environmental management of geothermal developments, worldwide, and particularly within those countries participating in an Environmental Annex of the Geothermal Implementing Agreement of the International Energy Association. This reflects a gradual change that has occurred in the philosophy of geothermal environmental management. The strategies developed include regulatory policies to achieve more efficient and sustainable use of renewable geothermal resources, while avoiding or minimizing adverse effects on the surface environment. Issues such as net changes in CO2 and H2S gas emissions, from natural vents and boreholes, are being addressed in terms of the global as well as the local effects. A key objective when undertaking environmental impact assessments is achieving a balance between adverse and beneficial effects through practical mitigation schemes. Production and reinjection strategies have evolved to be more flexible in order to react to adverse effects, such as major reductions in natural surface discharges and subsidence, without compromising the efficient utilization of the resource. The benefits of a well designed environmental monitoring program have been clearly demonstrated. Examples of positive environmental benefits arising from these changes have been documented. They include: hot stream restoration, the creation of new thermal features using waste hot water, subsidence-induced wetlands, increases in steam heated ground resulting from pressure drawdown, and increases in hot spring activity stimulated by shallow reinjection. These increases have subsequently created enhanced ecological habitats for rare thermophilic organisms and thermally tolerant vegetation.