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Greenhouse Gas Emissions after Application of Landfilled Paper Mill Sludge for Land Reclamation of a Nonacidic Mine Tailings Site

Faubert, Patrick, Durocher, Simon, Bertrand, Normand, Ouimet, Rock, Rochette, Philippe, Tremblay, Pascal, Boucher, Jean-François, Villeneuve, Claude
Journal of environmental quality 2017 v.46 no.5 pp. 950-960
Trifolium repens, carbon dioxide, climatic factors, emissions factor, greenhouse gas emissions, greenhouse gases, land restoration, landfills, methane, mine tailings, mining, nitrous oxide, pulp and paper industry, pulp and paper mills, pulp and paper sludge, reforestation, soil, sowing
Large areas of mine tailings are reclaimed by applying organic amendments such as paper mill sludge (PMS). Although mining industries can use PMS freshly generated by paper mills, operational constraints on paper industries make temporary landfilling of this material an unavoidable alternative for the paper industries, creating the most prominent PMS source for mining industries. This study aimed to quantify soil greenhouse gas (GHG) emissions (N₂O, CO₂, and CH₄) after application of landfilled PMS (LPMS; i.e., excavated from a landfill site at a paper mill) and LPMS combined with a seeding treatment of white clover (Trifolium repens L.) on nonacidic mine tailings site prior to reforestation. Soil N₂O, CO₂, and CH₄ fluxes were measured after applications of 50 and 100 Mg dry LPMS ha⁻¹ during two consecutive snow-free seasons on two adjacent sites; LPMS was applied once in the first season. The LPMS application increased N₂O emissions (7.6 to 34.7 kg N₂O-N ha⁻¹, comprising 1.04 to 2.43% of applied N) compared with the unamended control during the first season; these emissions were negligible during the second season. The LPMS application increased CO₂ emissions (∼5800 to 11,400 kg CO₂–C ha⁻¹, comprising 7 to 27% of applied C) compared with the unamended control on both sites and in both seasons. Fluxes of CH₄ were negligible. White clover combined with LPMS treatments did not affect soil GHG emissions. These new GHG emission factors should be integrated into life-cycle analyses to evaluate the C footprint of potential symbioses between the mining and paper industries. Future research should focus on the effect of PMS applications on soil GHG emissions from a variety of mine tailings under various management practices and climatic conditions to plan responsible and sustainable land reclamation.