The feasibility of an organic residual cover on mine tailings for the growth of biofuel crops

Mine tailings with an organic residual cover from the pulp and paper industry was used to test the development of an alternative land use for the growth of biofuel crops. In Northern Ontario, crops of short rotation dwarf corn and a northern variety of canola were grown on a mine tailings site and on an agricultural reference site for two growing seasons (2008 & 2009), to determine if this alternative land use could be feasible. The plant growth parameters measured, indicated that the crops grown at the tailings site had greater plant heights (p<0.01), biomass yields that were greater than, or equal to, those at the agricultural site (p<0.05), and greater grain yields for corn and seed yields for canola (p<0.05). Total and potentially bioavailable element levels were also determined for the organic residual cover. All total potential contaminant levels were below guidelines, with the exception of arsenic, but its bioavailability was low, and all total element levels were within typical ranges for soils in the northern Ontario mining community. The total element levels were also determined for both crops, and their various components. The root and shoot metal contents typically had the highest metal concentrations, but metals were not always excluded from the grain and seed portions. The metal concentrations within plant components were similar between both sites, with the agricultural site sometimes having higher levels. The high pH and organic matter content of the organic residuals aided in making the metals less bioavailable to the crops. No metal toxicity symptoms were observed for either crop.