Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING FARMS FOR ENVIRONMENTAL STEWARDSHIP AND PROFIT

Location: Pasture Systems & Watershed Management Research

Title: Predicting the emission of volatile organic compounds from silage systems

Authors
item Rotz, Clarence
item Hafner, Sasha -
item Montes, Felipe -
item Mitloehner, Frank -

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2014
Publication Date: July 13, 2014
Citation: Rotz, C.A., Hafner, S., Montes, F., Mitloehner, F. 2014. Predicting the emission of volatile organic compounds from silage systems[Abstract]. ASABE Annual International Meeting. p 1.

Technical Abstract: As a precursor to smog, emission of volatile organic compounds (VOCs) to the atmosphere is an environmental concern in some regions. The major VOC emission source from farms is silage, with emissions coming from the silo face, mixing wagon, and feed bunk. The major compounds emitted are alcohols with other important compounds being organic acids, esters, and aldehydes. A model was developed to predict emissions of these four groups of VOCs as affected by silage management, the environment, and their interactions. Emission of each of the important compound groups is predicted based upon their volatility, concentration in the silage, silage density, exposed surface area, wind speed, and temperature. Potential ozone formation from the total of all compounds is determined considering the reactivity of each compound group. This VOC emission model is included as a component of a farm simulation model (Integrated Farm System Model) where it is used to study management effects on silage emissions along with other farm emissions to air and water, production costs, and profitability. Effects of management factors such as the type of silage, type and size of storage facility, packing density, and feedout rate can be quantified and compared. To illustrate the use of the model, a representative dairy farm was simulated in central Pennsylvania. The farm included 100 high-producing Holstein cows plus replacements on 100 ha of cropland producing alfalfa and corn. Feeds produced and fed on the farm included 285 t DM of alfalfa silage, 254 t DM of corn silage and 220 t DM of high moisture corn grain all stored in bunker silos. The total annual emission of ozone-forming VOCs was 1361 kg with 63% coming from corn silage, 20% from high-moisture corn and 17% from alfalfa silage. Most of the emission came from the silo face (78%) with the remainder occurring during feed mixing and from the feed bunk. The use of large tower silos in place of bunkers reduced the total emission 1% with a 9% decrease in farm profit. Use of two smaller diameter silos in place of one larger tower silo reduced emissions 12%, but farm profitability was also reduced 8%. Use of silage bags reduced emission 22% while increasing farm profit 18%. Climate had an effect on emissions. Moving the farm to northern New York reduced the total emission 5%, and moving it to southern Virginia increased the emission 30%. Although data are not available to fully assess the validity of the model, preliminary evaluations have shown the model to predict reasonable emission levels and realistic responses to management changes. Farm scale data are now being collected for a more formal evaluation of the model. The goal is to use the integrated farm model to study VOC mitigation strategies for reducing emissions while maintaining or improving farm profitability. Future work will focus on model evaluation and incorporation of effects of silage additives and other strategies for reducing VOC emission.

Last Modified: 11/25/2014
Footer Content Back to Top of Page