Methane and nitrous oxide emissions from Canadian dairy farms and mitigation options: An updated review

This review examined methane (CH4) and nitrous oxide (N2O) mitigation strategies for Canadian dairy farms. The primary focus was research conducted in Canada and cold climatic regions with similar dairy systems. Meta-analyses were conducted to assess the impact of a given strategy when sufficient data were available. Results indicated that options to reduce enteric CH4 from dairy cows were increasing the dietary starch content and dietary lipid supplementation. Replacing barley or alfalfa silage with corn silage with higher starch content decreased enteric CH4 per unit of milk by 6%. Increasing dietary lipids from 3% to 6% of dry matter (DM) reduced enteric CH4 yield by 9%. Strategies such as nitrate supplementation and 3-nitrooxypropanol additive indicated potential for reducing enteric CH4 by about 30% but require extensive research on toxicology and consumer acceptance. Strategies to reduce emissions from manure are anaerobic digestion, composting, solid-liquid separation, covering slurry storage and flaring CH4, and reducing methanogen inoculum by complete emptying of slurry storage at spring application. These strategies have potential to reduce emissions from manure by up to 50%. An integrated approach of combining strategies through diet and manure management is necessary for significant GHG mitigation and lowering carbon footprint of milk produced in Canada

Experimental Analysis of the Interaction between Streamwise Vortices and a High-Lift Airfoil

The present paper presents experimental investigations of the interaction between streamwise vortices and a high-lift airfoil. A delta wing upstream of the high-lift airfoil generates two vortices, which proceed on the suction side of the airfoil and interact with the local flow field. The characteristics of the vortices resemble those of a nacelle strake vortex scaled to wind-tunnel dimensions. Measurements of the static pressure distributions and oilflow visualizations with and without the upstream located delta wing reveal the effect of the vortices on the high-lift airfoil. Furthermore, stereo-PIV measurements at different streamwise positions upstream of the high-lift airfoil and above the suction side show the development of the vortex characteristics. The investigations comprise variations of the angle of attack of the high-lift airfoil and the vertical position of the delta wing. The presence of the vortices clearly affects the flowfield of the high-lift configuration. Also, the characteristics of the vortex considerably change while proceeding downstream through an interaction with the flow field of the high-lift airfoil

Experimental and Numerical Analysis of a Streamwise Vortex Downstream of a Delta Wing

The present paper analyzes the vortical flow downstream of a delta wing. The Delta wing is designed to generate a vortex which resembles the vortex of a nacelle strake. The experimental results of stereo-PIV measurements performed at different positions downstream of the delta wing display the streamwise development of the vortex. The distributions of the mean axial and tangential velocity components and Reynolds-stresses characterize the vortex development. In addition, results of numerical simulations with the DLR TAU-code applying the Menter-SST eddy viscosity model and the SSG/LRR-Omega Reynolds-Stress model show the ability of the turbulence models to capture the vortex development. The experimental results indicate a preservation of the vortex strength and structure downstream of the delta wing. The Menter-SST model does not predict this preservation, rather it computes a rapid decay of the vortex strength and an increase of the vortex size. In contrast, the results of the SSG/LRR-Omega model are in good Agreement with the experiments concerning the mean flow development. However, turbulence in the vortex core is underpredicted by both turbulence models