A comprehensive model to estimate the simultaneous release of acidic and basic gaseous pollutants from swine slurry under different scenarios

Abstract

Swine slurry is a source of atmospheric pollutants. Emissions of basic and acidic compounds from slurry are largely dependent on the surface pH. In a storage system, the pH at the surface layers changes over time due to the volatilisation of ammonia (NH₃), carbon dioxide (CO₂) and acetic acid (HAc). In this article, a comprehensive gas emission–pH (GE–pH) coupled model is proposed to describe the simultaneous release of acidic and basic gaseous pollutants from swine slurry. The model was applied to describe the release of NH₃, CO₂, HAc and hydrogen sulphide (H₂S) from standard slurries stored in animal houses, outside storage tanks and lagoons. The modelled results agreed well with values reported in the literature and could be reasonably interpreted. The key parameters affecting the release of gases were: initial pH, initial concentration of total ammonium nitrogen and inorganic carbon, slurry temperature and air velocity. This study suggests that future modelling studies on gas emissions from animal slurry should consider the concentration of inorganic carbon and the frequency in which the slurry surface is mixed or altered, because they affect the surface pH and the release of gaseous pollutants from slurry.

Keywords:

• pH
• hydrogen sulphide
• ammonia
• carbon dioxide
• emission
• model
• slurry

Acknowledgements

The research was performed as part of research project ‘Reduction of Odor Source in and Emission from Swine Buildings’, under the Program ‘Animal Husbandry, the Neighbours and the Environment’ funded by the Danish Ministry of Food, Agriculture and Fisheries (Grant Number: 3304-VMP-05-032-01) and the research project StaldTek funded by The Danish Agency for Science, Technology and Innovation (The Danish Ministry of Science, Technology and Innovation).