Model for calculating ammonia emission from stored animal liquid manure

Abstract

Ammonia (NH3) emissions from agriculture have increased by 90% from 1970 to 2005, and agriculture is now the largest source of NH3 to the atmosphere. Calculated national NH3 emissions from agriculture using static emission factors do not reflect regional conditions. We propose, parameterize and test a simple model to calculate emission rates which incorporates effects of temperature, pH, total ammoniacal nitrogen (TAN) concentration, exposed storage area, and storage cover. This is the first time that several known algorithms were combined in this semi-dynamic user-friendly model concept and that model parameters (uploaded on the internet) were estimated from a unique database comprising 44 studies. The calculator is designed to be used correctly even if there exists only little knowledge about manure chemistry or micrometeorology, and can calculate emissions with a low demand for input data Calculations using the new model are as accurate as the standard method. The proposed approach has two advantages compared to the standard alternative: it does not require an estimate of TAN flow through the store, and calculated values reflect management (e.g., storage area or covers), TAN concentration, pH and temperature based on well-established principles. The simple and process-related approach has the potential to deliver more accurate estimates after a more precise parameterization from dedicated studies where the focus is on emission measurements, slurry composition characterization, air and slurry temperature and turbulence. To facilitate this approach, data need to be collected over relatively short time intervals (less than twice per day) to ensure that they cover cardinal diurnal conditions at the same time and right place. A spreadsheet implementation of the model is publicly available from https://github.com/sashahafner/AMOSTO.