Impact of Temperature and Mixing on Methane Production Rates of Swine Manures obtained from Deep pit Storages

Abstract

<p>The appearance of copious amounts of foam on the surface of deep-pit swine manure storages throughout the Midwestern United States is a serious concern for the pork industry. Manure foam has the capacity to trap gases produced by the anaerobic decomposition of the manure, leading to dangerous flammable gas concentrations upon agitation or foam disturbance. One potential cause of foaming is increased methane production from the manure. To this end, personnel at the Agricultural Waste Management Lab at Iowa State University developed a test to evaluate the methane production rate of manure. The goal of this work is to describe this assay, provide a basic summary and validation of the results it provides, and to evaluate the impact that agitation (shaken versus non-shaken) and temperature (5, 15, 25, and 35°C) had on the measured methane production rate of swine manure obtained from three swine finishing facilities in North Central Iowa. The experiment was conducted using a full factorial design with three treatments: manure source (a random variable), agitation (a fixed effect), and temperature (a fixed effect). The results indicated that the test is yielding methane production rates similar to those reported in literature. The results of the factorial experiment indicated that temperature significantly impacted the methane production rate in these tests, but that agitation did not. To better understand the impact of temperature methane production rates were plotted as a function of temperature and fitted to the Arrhenius equation. The results indicated that methane production rates approximately doubled with every 10°C increase in temperature.</p>