GHG Emissions from Manure in a Naturally Ventilated, Freestall Dairy Barn, Comparing Sand and Sawdust Bedding

Abstract

Concentrations and emissions rates of greenhouse gases CO2, CH4 and N2O frommanure on concrete alley floor were determined in a naturally ventilated, freestall Holstein dairy cowbarn with sand and sawdust bedding, in south coastal British Columbia, Canada. Gas samples forGHG analysis were collected in two separate experiments during the spring and summer using openchambers placed on the alley floor. Laboratory experiments were also conducted with chambers, onetesting different proportions of manure mixed with bedding, and the other using manure from thealley floor, with the two bedding materials. GHGs were analyzed using a gas chromatograph. Resultsfrom the barn and laboratory experiments showed significantly higher CO2 emission rate frommanure with sawdust (1,512 mg-1m-2hr-1) than from sand (1,272 mg-1m-2hr-1). However, a significantlylower N2O emission rate was recorded from sawdust (0.05 mg-1m-2hr-1) than from sand (0.22 mg-1m-2hr-1). Emission rate for CH4 was similar from both types of bedding. Emission loads from manure onthe barn floor followed the same pattern as the emission rates from each type of bedding. Both theemission rates and loads of GHGs in this study pertain mainly to bedding-littered manure on the alleyfloor, and essentially exclude GHGs released from the rumen and the lungs of the cows. Furtherstudies are needed to include all sources of GHG emissions in dairy barns.