Effects on Carbon and Nitrogen Emissions due to Swine Manure Removal for Biofuel Production
- Kim H. Weaver *a,
- Lowry A. Harperb and
- Sarah M. Brownc
- a Dep. of Physical Science, Southern Utah Univ., 351 W. Center, Cedar City, UT 84720
b USDA–ARS (retired); L.A. Harper, current address: Harper Consulting Co., Trace-Gas Emissions Consulting, P.O. Box 772, Watkinsville, GA 30677
c Dep. of Mathematics, Southern Utah Univ., 351 W. Center, Cedar City, UT 84720
Methane (CH4) and ammonia (NH3) are emitted from swine-manure processing lagoons, contributing to global climate change and reducing air quality. Manure diverted to biofuel production is proposed as a means to reduce CH4 emissions. At a swine confined animal feeding operation in the U.S. Central Great Basin, animal manure was diverted from 12 farms to a biofuel facility and converted to methanol. Ammonia emissions were determined using the De Visscher Model from measured data of dissolved lagoon ammoniacal N concentrations, pH, temperature, and wind speed at the lagoon sites. Other lagoon gas emissions were measured with subsurface gas collection devices and gas chromatography analysis. During 2 yr of study, CO2 and CH4 emissions from the primary lagoons decreased 11 and 12%, respectfully, as a result of the biofuel process, compared with concurrently measured control lagoon emissions. Ammonia emissions increased 47% compared with control lagoons. The reduction of CH4 and increase in NH3 emissions agrees with a short-term study measured at this location by Lagrangian inverse dispersion analysis. The increase in NH3 emissions was primarily due to an increase in lagoon solution pH attributable to decreased methanogenesis. Also observed due to biofuel production was a 20% decrease in conversion of total ammoniacal N to N2, a secondary process for the removal of N in anaerobic waste lagoons. The increase in NH3 emissions can be partially attributed to the decrease in N2 production by a proposed NH4+ conversion to N2 mechanism. This mechanism predicts that a decrease in NH4+ conversion to N2 increases ammoniacal N pH. Both effects increase NH3 emissions. It is unknown whether the decrease in NH4+ conversion to N2 is a direct or physical result of the decrease in methanogenesis. Procedures and practices intended to reduce emissions of one pollutant can have an unintended consequence on the emissions of another pollutant.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2012. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.