The Application of Hybrid media for the Mitigation of Methane Emissions through Biofiltration

Date
2018-04-17
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Abstract
The on-going annual increase in global CH4 emissions can be largely attributed to anthropogenic activities. However, as more than half of these emissions are diffuse and possess a concentration less than 3% (v/v), physical-chemical treatments are inefficient as an abatement technology. In this regard, biotechnologies, such as biofiltration using methane-oxidizing bacteria, or methanotrophs, are a cost-effective and efficient means to combat diffuse CH4 emissions. Utilizing a packing material such as biochar that has a high sorption potential may increase the contact time required for improving removal efficiencies of CH4. As CH4 biofiltration requires water addition to maintain microbial activity, the results from the adsorption experiments indicate adsorption capacity is not lost with water addition if biochar is the dominant packing material. Additionally, fixed bed columns of biochar may be a reliable back-up system to a hybrid system for CH4 biofiltration especially for high inlet loads. Generally, increasing the compost content of the packing material, water content, and inlet flow rate together has the most damaging effect on adsorption. The results from batch studies indicate lava rock and biochar can support the growth of methanotrophs for the oxidation of CH4 to CO2. Nitrogen additions of up to 191 g (N)/m3 matrix maximized oxidation activities but inhibited it at concentrations above this value. The methanotrophs likely enter into a starvation phase (or a stationary phase of growth where the population may cease to divide but remain metabolically active) in response to unfavorable nitrogen conditions and their CH4 oxidation activities eventually recover as toxic NH3/NO3 intermediates are further oxidized during nitrogen metabolism. Column biofiltration experiments demonstrated that a 7:1 volumetric mixture of biochar and compost can successfully remove up to 877 g CH4/m3·d with empty-bed residence times of 82.8 minutes. As a biologically-active material, compost served as the sole source of nutrients and inoculum for the biofilters which greatly simplified the operation of the system. Higher elimination capacities may be possible with higher compost content such as a 1:1 ratio of either biochar or lava rock, while maintaining the empty-bed residence time at 82.8 minutes.
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Keywords
Methane oxidation, Biofiltration, Greenhouse Gas, Methanotroph, Methane, Adsorption, Biochar, Lava rock, Compost
Citation
La, H. (2018). The Application of Hybrid media for the Mitigation of Methane Emissions through Biofiltration (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31808