Date of Award

Fall 1995

Project Type

Dissertation

Program or Major

Earth Sciences

Degree Name

Doctor of Philosophy

First Advisor

Robert Harriss

Abstract

Current waste management practices present significant potential for emissions of radiatively active trace gases to the atmosphere. This dissertation describes the quantitative assessment of nitrous oxide (N$\sb2$O) emissions from liquid waste and residuals treatment, emissions of methane (CH$\sb4$) from landfills, and the effects of microbial oxidation on landfill CH$\sb4$ emissions.

N$\sb2$O emissions were measured from liquid treatment process at a wastewater treatment plant where the highest emissions occurred during secondary aeration. Emission factors derived from the measurements included 3.2 g N$\sb2$O person$\sp{-1}$ year$\sp{-1}$ and $1.6\times10\sp{-6}$ g N$\sb2$O (liter wastewater$\sp{-1}$). The potential for N$\sb2$O emissions from the composting of the residual wastewater sludge was also investigated. Treatment by composting resulted in significant emissions yielding an emission factor of 0.7 g N$\sb2$O (dry kg of sludge)$\sp{-1}.$ In addition, potential N$\sb2$O emissions were predicted from the treatment of other organic wastes. Preliminary data from livestock waste and yard waste composting yielded emission factors of 0.5 g N$\sb2$O (dry kg)$\sp{-1}$ and 0.3 g N$\sb2$O (dry kg waste)$\sp{-1}$ from livestock and yard wastes, respectively. Livestock wastes were determined to present the greatest potential for global N$\sb2$O emissions, estimated to contribute 1.2 Tg year$\sp{-1}.$.

CH$\sb4$ emissions from the landfilling of municipal solid wastes were determined using static enclosure and atmospheric tracer methods. Favorable agreement was observed between whole landfill emission estimates, yielding values of 16200 and 16740 liters CH$\sb4$ min$\sp{-1}$ using the chamber and tracer methods, respectively. The influence of microbial oxidation on landfill CH$\sb4$ emissions was also investigated. Soil samples from locations of CH$\sb4$ flux were returned to the laboratory and subjected to incubation experiments to quantify the response of oxidation in these soils to temperature, moisture, in-situ CH$\sb4,$ soil depth, and oxygen. The mathematical representations of the oxidation responses were combined with measured and predicted soil characteristics in a computer model to predict the rate of CH$\sb4$ oxidation in the soils. Air temperature and precipitation data were used in conjunction with an existing soil climate model to estimate an annual whole landfill oxidation rate in 1994 of 11%.

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