Effect of increasing levels of corn silage in an alfalfa-based dairy cow diet and of manure management practices on manure fugitive methane emissions

The main objective of this study was to assess the effect of dairy cow diets and manure storage management practices on manure fugitive CH4 emission in order to precisely establish the carbon footprint of Canadian milk products. The specific objectives of this study were to investigate the effect of incorporating 50 and 100% corn silage (CS) as starch sources in dairy cow diets and the effect of complete removal of residual sludge in the manure storage tank and of storage emptying frequency on manure fugitive CH4 emissions. Alfalfa silage based diets were formulated as follows: 0% corn silage (0% CS, considered as the control diet); 50% corn silage (50% CS); and 100% corn silage (100% CS). Canadian summer manure storage conditions were simulated in laboratory-scale storage structures located in a controlled-environment chamber operated at 20 ± 1 °C. The incorporation of 50 and 100% CS in dairy diets was associated with significant increases of 39 and 79%, respectively, in fugitive CH4 emissions expressed in L day−1 cow−1 from manure storage with residual sludge over a 120-day storage period. The complete removal of residual sludge in the manure storage tank resulted in fugitive methane emission reductions exceeding 97.0% irrespective of the diet composition. Emptying of the manure storage tank 2 times and 4 times over the summer period reduced fugitive CH4 emissions on average by 40 and 80%, respectively. The complete removal of the manure storage residual sludge and the increase in manure storage tank emptying frequency over the summer can be adopted as low-cost best management practices (BMPs) for substantially reducing the fugitive CH4 emissions from manure storages.