Methane emissions from stored liquid dairy manure in a cold climate

Climate change has been linked to increasing concentrations of greenhouse gases including CH4, which has a global warming potential 25 times greater than CO2. Stored liquid animal manure is an important emissions source of CH4 globally and in Canada. As part of ongoing efforts to mitigate CH4 emissions, it may be beneficial to obtain field scale flux estimates which can be used to verify CH4 emission factors. The objective of this study was to measure CH4 fluxes from a liquid dairy manure storage tank and compare measured fluxes with predicted values using US EPA methodology. Fluxes were measured from a circular concrete tank 11.25 m in diameter storing liquid dairy manure in Bright, Ontario, Canada. Measurements were conducted semi-continuously from January through July 2003, using a tunable diode laser and the non-interfering micrometeorological mass balance method. Monthly average CH4 flux ranged from 11 mu g/m(2)/s in June after the tank had been emptied, to 153 mu g/m(2)/s in July. Large bubble flux events occurred in February and March that coincided with surface thawing. Predicted emissions using the US EPA approach with carryover of volatile solids showed overestimation unless a substantial correction factor was used. In contrast, if volatile solids were not carried over, predicted fluxes had acceptable agreement with measurements. This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture Finding a Balance between Food and Emissions, Guest Edited by TA. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hoo, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. (C) 2011 Elsevier B.V. All rights reserved.