A Mass Transfer Model of Ethanol Emission from Thin Layers of Corn Silage

A mass transfer model was developed and validated to predict ethanol emission from thin layers of corn silage. The model was developed using experimental data collected from silage placed in a wind tunnel under different temperatures and air velocities. Data from the wind tunnel experiments were used to derive a multiple regression equation that related the overall mass transfer coefficient of ethanol to temperature and air velocity. Evaluation of the model was done using data collected from experiments conducted in a controlled environmental chamber. Ethanol emission was determined from the ventilation rate of the environmental chamber and ethanol concentration in the chamber exhaust over a 24 h period, measured using a photoacoustic gas analyzer. Ethanol concentration in the silage was also monitored throughout the duration of each experiment. Predicted ethanol emission rates were strongly correlated (R 2 = 0.94) with values measured in the environmental chamber. A high correlation (R 2 = 0.96) was also found between predicted and measured ethanol concentrations in the silage. The model was used to estimate ethanol emission rates from thin layers of lightly packed silage on a dairy farm in California. Model predictions indicate that most of the ethanol contained in the silage could be emitted in the first 10 h after exposing the silage to ambient air temperature (18°C to 35°C) and air velocity (0.1 to 2.0 m s -1 ).