Promoting Terrestrial Carbon Sequestration On Reclaimed Mine Land through the Use of Coal-Fired Electric Power Generation by-Products.

Since 2000, the Tennessee Valley Authority, the Electric Power Research Institute, and the Department of Energy - National Energy Technologies Laboratory have been evaluating and demonstrating the integration of terrestrial carbon sequestration and the use of two electric power generation by-products: Flue Gas Desulfurization gypsum and ash pond process water. Through a series of greenhouse studies, American sycamore (Platanus occidentalis L.) and sweet gum (Liquidambar styraciflua L.) were chosen due to their tolerance to boron (phytotoxic and a major component of the FGD process), drought tolerance, growth rate and commercial value.  In 2002, the Carbon Capture and Water Emissions Treatment System (CCWESTRS) project was established on marginally reclaimed surface coal mine lands near TVA’s Paradise Fossil Plant in Muhlenberg County, Kentucky.

The primary measure of system effectiveness has been the ability of the system to sequester carbon, measured by assessing survival and growth response of plants within the CCWESTRS project.  Additionally, site soils and subsurface materials are being evaluated for their effectiveness at treating the irrigation water for various pollutants.  As early as three years after the initial field planting, American sycamore biomass had increased significantly as a function of greater mulch depth and total irrigation.  Sweet gums have not exhibited a similar response.  Below-ground carbon stocks decreased initially primarily due to the conversion from grasses and forbs to trees, but this trend has slowly reversed.  The greatest changes in soil chemistry across the site have been due to the use of FGD gypsum mulch and ash pond irrigation water which has resulted in higher levels of calcium and sulfur with depth.  Although boron levels in the irrigation water have reached concentrations as high as 8 mg/l and some leaf tissue concentrations have exceeded 250 ppm, very little toxicity symptoms have appeared in either tree species.