Mine Soil Remediation Using Coal Ash and Compost Mixtures

Abstract

Combinations of coal combustion ashes and composted animal manures may accelerate revegetation of drastically disturbed landscapes, such as surface mines. The objective of this study was to evaluate the effect of coal ash plus compost mixtures on soil chemistry and plant growth in acid mine soils. Scrubber sludge (flue gas desulfurization residue + fly ash) or bottom ash was mixed with three types of compost (dairy manure, poultry litter, and biosolids) at rates of 0, 33, 67 and 100% (v/v). The coal ash + compost mixtures were blended with acid mine soil (pH4.0) at rates of 15, 30, and 45% (v/v) (equivalent to 150, 300, and 450 dm³ m⁻³) and placed in pots in a greenhouse. Ryegrass seeds were planted in each pot and harvested after two months growth with no fertilization. Applying scrubber sludge residue alone at rates of 15, 30 and 45% (v/v) decreased ryegrass yield, but increased soil pH from 4.0 to 7.2, 7.1, and 7.6, respectively. The same rates of bottom ash increased soil pH to 5.2, 5.6, and 6.5, respectively, but had little effect on ryegrass yield. Composted dairy manure and biosolids increased ryegrass growth at rates up to 45% (v/v) when applied alone. Composted poultry litter increased ryegrass growth at a 15% rate, but decreased it at rates of 30 and 45% due to excess dissolved salts. Copper and Zn uptake were correlated to organic matter application rate. Leachate concentrations of P were increased by the addition of organic amendments and sulfur concentrations were increased by the addition of scrubber sludge. Bottom ash had no significant effect on heavy metal uptake or leachate composition. The results demonstrate that combinations of animal manure compost with coal combustion ashes can effectively stimulate biomass production in acidic surface mine soils.