Grant: Alliance Grants

Reduced sulfur compounds (RSC) such as hydrogen, carbon and methyl sulfide and disulfide are mostly gaseous pollutants that contain sulfur in its reduced state. They are implicated in odor production and have effects on human health and the environment. RSC along with biogenic methane (CH4) are associated with the storage and management of oil sands fluid fine tailings (FFT), a huge amount of waste produced during bitumen recovery from oil sands ore. Effective management of FFT is important for sustainable oil sands development in Alberta to meet energy demand. Untreated FFT or FFT treated with coagulant (gypsum or alum; sulfate-bearing compounds) are reclaimed by creating end-pit lakes (EPLs) and wetlands (as components of mine closure landform) where methanogenesis and sulfate reduction are the key anaerobic microbial processes. Anaerobic microbial metabolism of residual hydrocarbons in FFT generates CH4, and produces RSC in the presence of sulfate. Microbial pathways of RSC production and RSC distribution in gaseous, aqueous and solid phases in FFT have not been studied yet. The aim of this study is to investigate: (1) microbial metabolism of different types of organic compounds such as petroleum hydrocarbons sourced to diluents used in bitumen extraction process and bitumen itself, and polyacrylamide used as a flocculent in FFT treatment under sulfate-reducing conditions that will be created using gypsum or alum used as coagulants in FFT reclamation; (2) geochemical interactions (reactions) of RSC species with FFT constituents and RSC distribution in different FFT (aqueous, gaseous and solid) phases; and (3) entagled carbon, sulfur and iron cycling to assess RSC and methane (CH4) emissions as sulfate-reducing conditions with gypsum or alum can inhibit methanogenesis, a source of CH4 emissions to the atmosphere. Research findings will provide industry with scientific knowledge to devise/amend strategies to manage RSC and CH4 emissions from ponds, end-pit lakes and wetlands, meeting objectives of Alberta's air quality management system and Environment and Climate Change Canada for Canada's 2030 Emission Reduction Plan.