Methane emissions from southern High Plains dairy wastewater lagoons in the summer

Abstract

Methane is a greenhouse gas with a global warming potential 25-fold that of CO2, and animal agriculture is recognized as a source of CH4 to the atmosphere. Dairy farms on the southern High Plains of New Mexico and Texas (USA) are typically open lot, and sources of CH4 are enteric emissions from cattle and wastewater lagoons. Uncovered anaerobic lagoons are identified by the US Environmental Protection Agency as a source of CH4 in dairy manure management systems. Our objective was to quantify summer CH4 emissions from wastewater lagoons of a commercial dairy farm in eastern New Mexico. Research was conducted during 8 days in August (2009) at a 3500 cow open lot dairy farm with flush alleys. Methane concentration over three lagoons (total area of 1.8ha) was measured using open path laser spectroscopy. Background CH4 concentration was measured using a back-flush gas chromatography system with flame ionization. Wind and turbulence data were measured using a three-axis sonic anemometer. Emissions were estimated using an inverse dispersion model. Methane concentrations in the air over the lagoons ranged from 3 to 12ppm, and averaged 5.6ppm, with a background CH4 concentration of 1.83ppm. Methane flux density (i.e., emission rate/unit area) ranged from 165 to 1184μg/m2/s, with a mean daily CH4 flux density of 402kg/ha/d. Methane emission rate averaged 0.211kg/head/d. Uncovered anaerobic lagoons were a source of CH4 emitted from this southern High Plains dairy farm, and lagoons could be a control point for emission reductions.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.