Emission of ammonia and other contaminant gases from naturally ventilated dairy cattle buildings

Emission of contaminant gases from livestock buildings is a major source of pollution within agriculture. Much research has been performed to find technical solutions that may be used to reduce these emissions. However, information and data on emissions from open cattle buildings are still needed in order to establish reliable emission models. Data related to different floor types and manure-handling methods are also crucial for the evaluation and improvement of housing equipment and production management. An investigation was carried out to provide fundamental knowledge on gas emissions from naturally ventilated dairy cattle buildings with different floor types and manure-handling systems. Emission rates of NH3, N2O and CH4 were determined from measured values of gas concentrations and calculated values of air exchange rates. In this paper, the methods to determine the air exchange rates in the naturally ventilated buildings are presented and discussed on the basis of the tracer gas method and the CO2 production model for the animals. In all cases, the NH3 emission rate increased with temperature, but the increase was highly dependent on floor type and manure system. In this article the emission rate is given as g HPU(-1) d(-1) where HPU is defined as 1000 W total heat produced by the livestock at an environmental temperature of 20 degrees C. In most buildings, the emission level increased from about 10 to 30 g HPU(-1) d(-1) as the temperature increased from 2 to 20 degrees C with a standard deviation from 0.5 to 9 g HPU(-1) d(-1). The highest emission rate measured was 75 g HPU(-1) d(-1) at 22 degrees C with a standard deviation of 15 g HPU(-1) d(-1). The emission rates were dependent on floor type and manure-handling method. The lowest ammonia emission was found for buildings with solid floors with smooth surface, scraper and drain. For buildings with slatted floors, manure treatment with acid, scraper on the slatted floor surface or channel scraper are potential alternative methods for reduction of the ammonia emission.