Technical Abstract: Silage on dairy farms has been recognized as an important source of volatile organic compounds (VOCs) to the atmosphere, and therefore a contributor to tropospheric ozone. Considering reactivity and likely emission rates, ethanol, 1-propanol, and acetaldehyde probably make the largest contribution to ozone formation. Accurate estimates of emission rates of these compounds are not available. Previous studies have measured VOC emission rates using flux chambers, which underestimate rates in the field, or wind tunnels, which may provide more accurate estimates. In this work we describe a mass balance approach for estimating VOC emission from cattle feed, and measurements of ethanol, 1-propanol, methanol, and acetaldehyde emission from corn silage on a dairy farm in Maryland, USA. We anticipate that our approach will provide more accurate estimates of emission rates and the effect of temperature and air flow on emission from silage under farm conditions.