Visiting Speaker - Dr. Daniel S. Grégoire

Geological Sciences and Geological Engineering Distinguished Speaker Program presents Dr. Daniel S. Grégoire 

On Tuesday, February 7, Dr. Daniel S. Grégoire, Carleton University, Department of Chemistry, will be giving a talk for the Queen's Department of Geological Sciences and Geological Engineering.

Biography: I have over 15 years of experience conducting research in the academic, private, and public sectors. My research focusses on the role microbes play in controlling the fate of contaminants in the environment. For my Ph.D. at the University of Ottawa, I worked with Dr. Alexandre Poulain and discovered new pathways for mercury cycling controlled by photosynthetic microbes. I translated these discoveries into bioremediation strategies for mining effluent through our company Microbright. After my Ph.D., I contributed to advancing open data policies with the International Development Research Centre before starting a Banting Postdoctoral Fellowship with Dr. Laura Hug at the University of Waterloo. My work with Dr. Hug leveraged whole-community DNA approaches such as metagenomics alongside geochemical analyses to characterize microbes involved in contaminant cycling in landfills and mining sites. Since then, I’ve started the Environmental Biogeochemistry and Biotechnology research group at Carleton. My lab focusses on using metagenomics and enrichment culturing to develop sustainable waste reclamation strategies for one of Earth’s fastest growing waste streams: e-waste.

Abstract: Landfills generate outsized environmental footprints due to microbial degradation of organic matter in municipal solid waste, which produces the potent greenhouse gas methane. With global solid waste production predicted to increase 69% by the year 2050, there is a pressing need to better understand the biogeochemical processes that control microbial methane cycling in landfills. In this study, we had the rare opportunity to characterize the microbial community responsible for methane cycling in landfill waste covering a 39-year timeframe. We coupled long term geochemical analyses to whole-community DNA (i.e., metagenomic) sequencing and identified key features that shape methane cycling communities over the course of a landfill’s lifecycle. Anaerobic methanogenic microbes are more abundant, diverse, and metabolically versatile in newer waste, fueling rapid methane production early in a landfill’s lifecycle. Aerobic methanotrophs were repeatedly found in leachate where low levels of oxygen were present and exhibited adaptations that aid survival under steep redox gradients in landfills. The potential for anaerobic methane oxidation, which has historically been overlooked despite anoxic habitats dominating landfills, was prevalent in a 26-year-old landfill cell which was in a state of slow methanogenesis. Finally, we identified the metabolic potential for methane oxidation in lineages that are widespread in aquatic and terrestrial habitats, whose capacity to metabolize methane remains poorly characterized. Ultimately, this work expands the diversity of methane cycling guilds in landfills and outlines how these communities can curb methane emissions from municipal solid waste.