Exploring Mixed Packing Media as a Means of Improving Methane Biofiltration

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Author:
Grabowski, Caitlin
Area of Honors:
Agricultural and Biological Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Juliana Vasco-Correa, Thesis Supervisor
Heather Elise Preisendanz, Thesis Honors Advisor
Keywords:
methane
green house gases
biofilter
packing media
nitrous oxide
hybrid biofilters
gas chromatography
Abstract:
Methane and nitrous oxide are potent greenhouse gases that are prevalent in diffuse concentrations in animal housing facilities. Finding efficient ways to maximize methane oxidation is key, and the use of bulking media like perlite and vermiculite has been suggested to enhance methane oxidation in biofilter systems. The goals of this study were to use gas chromatography to (1) compare the performance of a vermiculite-compost and perlite-compost biofilter with respect to their methane, nitrous oxide and carbon dioxide fluxes over time and (2) to determine the effectiveness of the vermiculite-compost and perlite-compost biofilter compared to non-hybrid design consisting of only a compost fraction. The bottle-sized reactors were designed with a 55% (w.b) moisture content and initial injection of 1 %v/v % v / v methane. The hybrid bottles contained 14 dry g of packing media in a 1:1 dry mass ratio and the compost-only bottles contained the equivalent compost fraction. This study found that both the vermiculite-and perlite-containing biofilters were more efficient at oxidizing methane than the compost controls. The compost controls demonstrate that while compost itself can provide adequate methane oxidation, the addition of a vermiculite or perlite fraction appeared to improve biofilter performance. In addition, the vermiculite bottles performed significantly better in terms of methane consumption, achieving the highest rate of oxidation that occurred earliest, suggesting a higher capacity to support methanotrophic activity than a biofilter of perlite and compost or compost only. While it oxidized the most methane, the vermiculite bottles also produced on average greater levels of carbon and nitrous oxide, indicating a tradeoff between methane reductions and nitrous oxide production in biofilters.