Evaluation of municipal solid waste (MSW) compost as a soil amendment for acidic, metalliferous mine tailings

Four 0.5 ha plots were established on freshly dried tailings of INCO Ltd. near Sudbury, Ontario, Canada and received the following treatments: 1) 125 t/ha Municipal Solid Waste (MSW) compost, 2) 250 t/ha MSW compost, 3) INCO's standard application of crushed limestone, fertilizer and hay mulch and 4) control - no application of compost. Application of compost at a rate of 250 t/ha yielded the same increase in tailings pH (from 2.80 to 4.65) as that achieved with the typical INCO application of 40 t lime/ha. The INCO treatment with lime and fertilizer resulted in no initial input of organic matter; whereas, a 250 t/ha application of compost increased organic content by 8.3%. Moisture retention in tailings at the two compost-treated plots was significantly higher (26%) than that of the INCO treated plots (<10%). Application of lime as part of the INCO treatment reduced levels of water soluble Cu and Ni from 22.8 μgCu/g to 0.4 μgCu/g and from 35.5 μgNi/g to 5.2 μgNi/g. Similar reductions in water soluble copper and nickel in tailings were achieved with the 250 t/ha application of compost. It was concluded that tailings amelioration with MSW compost is superior to the INCO treatment because it more rapidly increases pH, moisture content and organic content, and reduces concentrations of water soluble (plant available) Cu and Ni.