Title: Methane emissions from Southern High Plains dairy wastewater lagoons in the summer Authors
Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 2010
Publication Date: June 23, 2011
Citation: Todd, R.W., Cole, N.A., Casey, K.D., Hagevoort, R., Auvermann, B.W. 2011. Methane emissions from Southern High Plains dairy wastewater lagoons in the summer. Animal Feed Science And Technology. 166-167:575-580. Interpretive Summary: Methane is a powerful greenhouse gas that contributes to global warming. Sources of methane at dairies include milk cows and wastewater lagoons, and the contributions into the atmosphere of these gasses is important to quantify. For six days in the summer, we measured methane levels at dairy lagoons along with the speed, direction, and turbulence of wind. Then, a computer model was used that simulates how these gases are released into the atmosphere to predict total methane emission from the dairy. The background level of methane in the air was 1.8 parts methane per million parts of air (ppm). Methane levels increased over the lagoons and ranged from 3 to 12 ppm. This showed that the lagoons released methane. We calculated that from 165 to 1184 micrograms per square meter per second were emitted. Daily release of methane averaged 402 kilograms per hectare per day. This represented 0.21 kilograms of methane released for each cow in the dairy. These results show that uncovered anaerobic lagoons can be a significant source of methane at dairies and also offer a potential location where methane loss can be reduced.
Technical 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 CH4to 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 from wastewater lagoons. Uncovered anaerobic lagoons are identified by the U.S. Environmental Protection Agency as a source of CH4 in dairy manure management systems. Our objective was to quantify summer CH4 emissions from the 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 1.8 ha) was measured using open path laser spectroscopy. Background CH4concentration 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 12 ppm, and averaged 5.6 ppm, with a background CH4 concentration of 1.83 ppm. Methane flux density (emission rate per unit area) ranged from 165 to 1184 ug/m2/s, with a mean daily CH4 flux density of 402 kg/ha/d. Methane emission rate averaged 0.211 kg/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 reduction.