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Title: METHANE EMISSIONS FROM AN ANAEROBIC SWINE LAGOON IN NORTH CAROLINA

Author
item Sharpe, Ronald
item Harper, Lowry

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Atmospheric concentration of CO2, CH4, and N2O have increased about 13%, 145%, and 15%, respectively since about 1750, and the mean global surface temperature has had a real increase of 0.3 to 0.6 C above normal variations since the late 18th century. Most countries, including the U.S., are not waiting for a direct cause and effect relationship to be proved and are taking steps to reduce greenhouse gas emissions. Methane is the most rapidly increasing greenhouse gas and accounts for about 27% of all climate forcing. Methane emissions from animal waste are estimated at about 28,000,000 metric tons per year or about 6 to 10 percent of annual anthropogenic emissions. United States agriculture needs accurate and reliable information on its contribution to CH4 emissions to identify possible areas for reduction. In a previous study, we found CH4 emissions from a swine lagoon to be related to windspeed and water temperature. This sstudy confirmed these relationships and also showed that including the quantity of volatile solids entering the lagoon greatly improved the predictive model for estimating lagoon emissions. At a 'farrow-to-finish' farms emissions ranged from 4 to 6 kg CH4/animal unit/yr. At a 'farrow-to- wean' farm emissions were less (1.6 kg CH4/animal unit/yr) probably due to the type of feed and manure handling system. Calculations using the data from this study would result in an estimated emission of about 188,000 metric tons/yr from anaerobic swine lagoons in the U.S. Reports by the EPA have estimated CH4 emissions rates from biogas production studies with covered lagoons which greatly affect ambient conditions and from the total CH4 producing potential of manure. Our emission estimates are about 22% of the current EPA estimates for CH4 emissions from swine lagoons.

Technical Abstract: Methane (CH4) emissions from swine waste holding lagoons were determined periodically in 1997 and 1998. Micrometeorological techniques allowed emission rates from the lagoon to be measured under ambient conditions with little disturbance to the natural environment. One farm (NC1) had about 13,700 animals and used a periodic 'flush' to remove wastes (about an 8-hr cycle). The second farm (NC2) had about 4,300 animals and used a 'pull- plug' system with a cycle time of about one week. In general, flux rates followed a diurnal pattern with greater fluxes during the day when both temperature and windspeed were greatest. Methane emissions from the lagoons were related to windspeed, air and water temperature and volatile solids loading into the system. Average emissions from one lagoon ranged from 20 to 115 kg CH4/ha/d. Emissions from the second lagoon were much less (8 to 11 kg CH4/ha/d) due to fewer numbers of animals,diet and type of fmanure handling system. The seasonal flux rates were averaged to calculat annual emissions from the two lagoons, which were 75 and 8 kg CH4/ha/d which corresponded to 4.1 and 1.6 kg CH4/animal/yr, respectively.