Abstract

Re-vegetation on closed mining-sites for carbon sequestration and/or bio-energy production is one of the strategies of addressing the world-wide issues of energy crisis and global warming. However, mine soils including coal-mining refuse usually have poor quality and are unfavorable to plant growth. Thus, the major objective of this study was to improve quality of coal-mining refuse under laboratory conditions using zeolite, flue gas desulfurization gypsum (FGD), flyash, and biosolids at 10% (w/w) rate. Chemical analysis did not indicate any significantly high concentrations of toxins in the solid or the solution phase, suggesting that soil acidity was the principal chemical constraint hindering re-vegetation. In this context, FGD was the best among the tested materials for increasing soil pH and improving lettuce (Lactuca sativa) seed germination, while application of biosolids significantly enhanced soil aggregate stability. Specifically, laboratory tests showed that application of FGD increased pH of the acidic coal refuse samples from initial 3.80-4.66 to 5.70-6.60 and enhanced the growth of germinated lettuce seedlings in mine soil solution from 2.9-4.4 cm to 5.9-8.6 cm. The biosolids amendment increased the geometric mean diameter of the mine soil aggregates from the antecedent 0.93-0.99 mm to 1.13-1.25 mm. However, use of zeolite and fly-ash did not significantly improve the soil quality.

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