Estimation of ammonia emission episodes for a national inventory using a farmer survey and probable number of field working days

Abstract

Emissions of ammonia (NH3) and odor from livestock operations, and particularly from the landspreading of manure, are an issue from many aspects. Regional and national issues include production of inhalable aerosols (PM2.5), where NH3 from agriculture is a critical precursor. This process is episodic. As a result, it is important to characterize the episodic nature of NH3 emissions. This paper addresses the fact that weather and soil conditions can focus manure landspreading into a relatively few days each year. The Versatile Soil Moisture Budget (VSMB) was used with 30 yr of weather data on 2576 soil landscape units in Canada to estimate the number of days in each month when manure spreading would be possible. In addition, a national survey of about 3100 livestock farmers was used to quantify common practice. The stochastic information from the VSMB and the survey were applied to an NH3 emissions model. The base case, invoked by most national NH3 emission inventory calculations, is that emissions are uniformly distributed throughout each month. The result of our study was that daily NH3 emission fluxes could be up to 20-fold higher in the spring and fall months when manure landspreading is common but when weather and soil conditions limit the number of days available for field work. This has direct implications for estimating the role of agricultural NH3 on the episodic production of PM2.5, and this approach also has application to odor management. Key words: Modeling, livestock, emission factor, odor, NH3, field working day