The environmental impact of ash management in coal-based power generation

The coal-based power generation industry faces increased pressure to improve its environmental performance in the light of concerns over greenhouse gas emissions, water availability and releases of both acid gases and metals to air and water. Assessment of its environmental performance requires a methodology whereby all environmental impacts can be assessed accurately in full cognisance of their spatial and temporal dimensions, while taking into account the social acceptability of technologies employed. In this work, a methodology is developed to determine the environmental impact associated with solid wastes generated by this industry, and the application of this to the specific case of ash management is demonstrated. This methodology involves a consideration of leachate generation processes from ash impoundments, and subsequent mobility of leached components into groundwater, with due attention given to an analysis of pertinent physico-chemical phenomena. This analysis results in the identification of a time-dependent concentration profile of mobile constituents at the interface between the ash impoundment and the surrounding environment. The integration of leachate prediction modelling with plume dispersion modelling tools provides a measure of the extent to which a land mass is affected by any subsequent leachate migration. In this way it is possible to obtain a time dependent footprint of affected land which could be used as a semi-site specific indicator of the environmental impact of solid waste management practices.