Conference Agenda

Two full-scale demonstration projects using coal combustion residues (CCRs) to reclaim abandoned mines were carried out near the Conesville and Cardinal coal-fired power plants located in eastern Ohio. Water quality data collected over ten year period from 2010 to 2020 were analysed to assess the environmental impacts associated with this mine reclamation approach. Statistically significant water quality changes were observed at both sites after reclamation began. By using linear discriminant analysis on the hydrogeochemcial characteristics of the water samples, we identified if the backfilled CCRs have observable influences on the water qualities of the underlying shallow aquifers.

Leachate from 26 decadal-duration laboratory tests on tailings isolated the time-dependence of sulfide mineral oxidation from field scale sources of variability. Time series from all tests show a three-phase evolution, with an order-of-magnitude decrease in sulfate release rate during the second phase. The first phase is relatively short (0.7-yr avg.), with large, quasi-steady release rates. In the second phase—of two- to six-years duration—release rates show a power-law dependence on time. Third-phase release rates are near detection limits and quasi-steady or slowly decaying. We attribute the second evolutionary phase to an accumulation of weathering products that hinders sulfide oxidation.

Two hundred years of hard coal mining in Germany ended in 2018. During the phasing out process one of many challenges will be the reduction of the environmental impact of organic substances. Operating fluids which had to be used in the past for safety reasons (e.g. non-inflammable hydraulic liquids containing polychlorinated biphenyls (PCB)) which are now known as toxic.

With regard to the Water Framework Directive and the resulting German surface water regulation, the quality of surface water needs to be improved. RAG addresses this task by deriving a multi-lane concept in cooperation with DMT and the water authorities.

Hard coal mining is one of the major source for anthropogenic methane emissions. Even after mine closure, methane is still released over a longer period. Experts assume that methane degassing will gradually drop due to the water rising because hydrostatical pressure will reduce the desorption from the seams. However, some scientists have already proved that mine water can contain methane-producing bacteria. This secondary methane geneses potential has not been analysed since then. The authors postulate that bacteria can generate recent methane even in mine water rebound processes. In this paper, they describe their approach to support this thesis.