Microbial methane from subsurface organic-rich units such as coals and shale support approximately 5% of the United States and Canada's energy needs. In the deep subsurface, microbial methane is formed by the metabolism of primarily CO2, H2, and acetate by methanogens. These metabolites are the by-products of multi-step biodegradation of complex organic matter by microbial consortia. This study investigates microbial methane in the Illinois Basin, which is present in organic-rich shallow glacial sediments (surficial), Pennsylvanian coals (up to 600 m depth), and the Upper Devonian New Albany Shale (up to 900 m depth). Findings from the study show that hydrogeochemical conditions are favorable for methanogenesis in each reservoir, with a decrease in groundwater flushing rates corresponding to a decrease in average reservoir depth and an increase in carbon isotopic fractionation. The deeper reservoirs (coals and shale) were paleopasteurized, necessitating re-inoculation by methanogens. The microbes were likely advectively transported from shallow sediments into the coals and shale, where areas of microbial methanogenesis correlate with freshwater recharge. The recharge in the shale was primarily sourced from paleoprecipitation with minor contributions from glacial meltwater during the Pleistocene (4He ages). All areas sampled in the shale were affected by Pleistocene recharge, however groundwater ages in areas of microbial methanogenesis are younger (average 0.33 Ma) than areas with thermogenic methane (average 1.0 Ma). Estimates of in-situ microbial methane production rates for the shale (10-1000 TCF/Ma) are 104-106 times slower than laboratory rates. Only limited biodegradation is observed in the shale. In-situ stimulation of methane production may be most effective if aimed at increasing production of the supporting microbial consortia as well as methanogens. Trace metal concentrations in the shale are below known levels of inhibition or enhancement, with the exception of Fe, suggesting that microbial methanogenesis is not repressed by any of the measured trace metals and may be improved with the addition of Ag, Co, Cr, Ni, and Zn.

Hydrochloric acid leaching of saprolite nickel ores has been proposed as an effective means of recovering nickel and cobalt. However, the leach produces a concentrated brine of magnesium chloride which must be hydrolyzed to recover the HCl lixiviant. The processing of carnallite similarly produces a concentrated MgCl2 brine; converting this brine into HCl and MgO provides an attractive way of adding value while effectively disposing of this waste product. Direct pyrohydrolysis of magnesium chloride brines by the reaction, MgCl2,a + H2Oa  MgOs + 2HClg is energy-intensive as large volumes of water must be evaporated. The energy cost is high, and the HCl stream produced is limited to approximately 20 wt% HCl. This thesis explores alternative methods of obtaining HCl from aqueous magnesium chloride solutions. Two methods are considered: the hydrolysis, under autogenous pressure, of concentrated MgCl2 molten salt hydrates; and the precipitation of magnesium hydroxychloride compounds such as 2MgO·MgCl2·6H2O and 3MgO·MgCl2·11H2O, which are subsequently decomposed at high temperature. Considerable experimental difficulties were encountered in studying pressure hydrolysis of molten salt hydrates, despite extensive equipment modifications. Ultimately, the work moved on to precipitation and decomposition of hydroxychlorides. This was found to bear promise, and conceptual flowsheets based on these reactions are presented. A phase stability diagram giving the areas of predominance of the different hydroxychloride phases is presented, and fundamental thermochemical data are derived. The results of a kinetic study on magnesium hydroxychloride thermal decomposition are also presented. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2011-03-11 10:14:53.455

Thesis (Ph. D.)--University of Wyoming, 2005. / Title from PDF title page (viewed on Nov. 1, 2007). Includes bibliographical references (p. 179-192).

Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on April 11, 2008). Includes bibliographical references.

Thesis (Ph. D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Sept. 1, 2009). Includes bibliographical references.

Thesis (Ph.D.)--University of Wyoming, 2009. / Title from PDF title page (viewed on June 10, 2010). Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 160-173.

The deep-sea hypersaline lakes in the Red Sea are among the most challenging, extreme, and unusual environments on the planet Earth. Despite their harshness to life, they are inhabited by diverse and novel members of prokaryotes. Methanogenesis was proposed as one of the main metabolic pathways that drive microbial colonization in similar habitats. However, not much is known about the identities of the methane-producing microbes in the Red Sea, let alone the way in which they could adapt to such poly extreme environments. Combining a range of microbial community assessment, cultivation and omics (genomics, transcriptomics, and single amplified genomics) approaches, this dissertation seeks to fill these gaps in our knowledge by studying archaeal composition, particularly methanogens, their genomic capacities and transcriptomic characteristics in order to elucidate their diversity, function, and adaptation to the deep-sea brines of the Red Sea. Although typical methanogens are not abundant in the samples collected from brine pool habitats of the Red Sea, the pilot cultivation experiment has revealed novel halophilic methanogenic species of the domain Archaea. Their physiological traits as well as their genomic and transcriptomic features unveil an interesting genetic and functional adaptive capacity that allows them to thrive in the unique deep-sea hypersaline environments in the Red Sea.

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