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All Subjects: Ammonia
Creators: Ermanoski, Ivan

Building microbial communities and managing fermentation in microbial electrolysis cells

Description

Microbial electrochemical cells (MXCs) offer an alternative to methane production in anaerobic water treatment and the recapture of energy in waste waters. MXCs use anode respiring bacteria (ARB) to oxidize organic compounds and generate electrical current. In both anaerobic digestion and MXCs, an anaerobic food web connects the metabolisms of different microorganisms, using hydrolysis, fermentation and either methanogenesis or anode respiration to break down organic compounds, convert them to acetate and hydrogen, and then convert those intermediates into either methane or current. In this dissertation, understanding and managing the interactions among fermenters, methanogens, and ARB were critical to making developments in MXCs. Deep sequencing technologies were used in order to identify key community members, understand their role in the community, and identify selective pressures that drove the structure of microbial communities. This work goes from developing ARB communities by finding and using the best partners to managing ARB communities with undesirable partners. First, the foundation of MXCs, namely the ARB they rely on, was expanded by identifying novel ARB, the genus Geoalkalibacter, and demonstrating the presence of ARB in 7 out of 13 different environmental samples. Second, a new microbial community which converted butyrate to electricity at ~70% Coulombic efficiency was assembled and demonstrated that mixed communities can be used to assemble efficient ARB communities. Third, varying the concentrations of sugars and ethanol fed to methanogenic communities showed how increasing ED concentration drove decreases in methane production and increases in both fatty acids and the propionate producing genera Bacteroides and Clostridium. Finally, methanogenic batch cultures, fed glucose and sucrose, and exposed to 0.15 – 6 g N-NH4+ L-1 showed that increased NH4+ inhibited methane production, drove fatty acid and lactate production, and enriched Lactobacillales (up to 40% abundance) above 4 g N-NH4+ L-1. Further, 4 g N-NH4+ L-1 improved Coulombic efficiencies in MXCs fed with glucose and sucrose, and showed that MXC communities, especially the biofilm, are more resilient to high NH4+ than comparable methanogenic communities. These developments offer new opportunities for MXC applications, guidance for efficient operation of MXCs, and insights into fermentative microbial communities.

ContributorsMiceli, Joseph (Author) / Torres, César I (Thesis advisor) / Krajmalnik-Brown, Rosa (Thesis advisor) / Rittmann, Bruce (Committee member) / Arizona State University (Publisher)

Created2015

Metallic Nitride Synthesis for Applications in Thermochemically Looped Ammonia Production

Description

Ammonia is one of the most critical chemical commodities produced and is integral to a number of current industries such as agriculture as well as a key part to future sustainability areas such as clean H2 production. However, the current production methods for ammonia are largely unsustainable and produce large amounts of CO2 emissions. This combined with the current dependence on fossil energy for production has led to researchers attempting to develop a clean and sustainable method for ammonia production. This method involves the thermochemical looping of a nitride compound with H2, and the renitridation of the compound with N2. This thermochemical loop would significantly reduce pressure requirements for ammonia production in addition to only being reliant on renewable inputs. This paper expands and complements this research by detailing the methods for the synthesis of nitride compounds as well as confirming their structure through material characterization. The nitride compounds as well as their oxide precursors were synthesized through Pechini synthesis and co-precipitation, and their structure was confirmed through the use of X-ray diffraction analysis. The XRD patterns of the synthesized nitrides matched those previously synthesized as well as those found in literature. In addition, observation of the spectra for the oxide CoMoO4 showed a marked similarity to that of the oxide precursor for (NixCox)2Mo3N. However, further testing is necessary regarding the phase-purity of synthesized nitrides, as well as the reduction and renitridation capability of nitrides in the line of (NixCox)2Mo3N.

ContributorsShakeel, Syed (Author) / Ermanoski, Ivan (Thesis director) / Miller, James (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)

Created2023-05