REVEGETATION OF COARSE TACONITE IRON-ORE TAILING USING MUNICIPAL SOLID-WASTE COMPOST

On Minnesota's Mesabi Iron Range, coarse taconite iron ore tailing is often used as the principal material in the construction of dams for large tailing impoundments. Mineland reclamation rules in Minnesota require that tailing dams be vegetated to control erosion for dam stability and safety. Coarse taconite iron ore tailing is characterized chemically by an alkaline pH, low organic matter content, lack of plant-essential nutrients, and low cation exchange capacity; physically by its coarse texture, lack of structure, low water-holding capacity, and dark color; and biologically by a lack of microorganisms. To investigate the potential of composted municipal solid waste to ameliorate these conditions and make the material more amenable to plant establishment and growth, the US Bureau of Mines implemented a series of factorial experiments at two active taconite mine sites in northeastern Minnesota. At each experimental site, vegetative cover has improved depending on the type of municipal solid waste compost used and rate of application. At site I, overall plant cover across all treatments has improved from zero prior to experimental manipulation to 72% after four years, with seven treatment combinations exceeding 90% cover. At site II, overall plant cover has improved from zero prior to experimental manipulation to 83% after four years, with 23 treatment combinations exceeding 90% cover. At both sites, total cover has progressively increased over four years and has not reached steady-state conditions. These results suggest a possible new strategy for reclaiming difficult sites through the use of municipal solid waste compost.