Source : Dairy Farmers of Canada (DFC) - Dairy Farmers of Canada (DFC)

This project, which was carried out under the supervision of AAFC in Lennoxville, Quebec, compared greenhouse gas (GHG) emissions from cows and from manure on dairy farms with different levels of milk production and different management practices. The project consisted of two components. The first component involved identifying practices that limit GHG emissions, while maintaining herd productivity. The second component involved demonstrating the potential that biofiltration has for reducing methane emissions from cow barns and manure pits on commercial dairy farms.

First component

On two different farms, gas-measuring equipment was installed to permit continuous sampling and analysis of the air entering and exiting mechanically ventilated cow barns. This was done to determine the amount of methane produced indoors by the animals. The two farms differed in terms of cow breed, diets and supplements used, number of meals per day and manure management practices. At both farms, peak emissions were found to be correlated with the animals’ feeding schedule. A single cow produces between 350 L and 650 L of methane per day. There are several ways to treat these emissions and to reduce the methane level in the exhaust air from cow barns. Cost and environmental effects are important considerations in choosing a technique for this purpose.

Second component

Biofiltration appears to be a promising approach; this natural process uses bacterial oxidation for the aerobic degradation of contaminants in air streams. The contaminants are absorbed and then oxidized by the microorganisms in the biofilter medium (e.g., peat, compost, wood chips). The microbes “eat” the particles of methane, converting them into the less harmful gas carbon dioxide and water. A large-scale experimental biofilter was developed and built. It has four compartments, each with a different filtering medium. The biofilter was mounted on a trailer so it could be moved from farm to farm to evaluate its effectiveness in oxidizing methane from different sources. Based on preliminary results, a methane reduction efficiency of 80% is attained for concentrations of 0.5% to 2.5%.