Emission of volatile organic compounds as affected by beef cattle diet and soil water content

Authors: Woodbury, Bryan; Gilley, John; Parker, David; MARX, DAVID - University Of Nebraska

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2021
Publication Date: 1/24/2022
Citation: Woodbury, B.L., Gilley, J.E., Parker, D.B., Marx, D.B. 2022. Emission of volatile organic compounds as affected by beef cattle diet and soil water content. Transactions of the ASABE. 65(1): 123-133. https://doi.org/10.13031/ja.14587.
DOI: https://doi.org/10.13031/ja.14587

Interpretive Summary: Emission of volatile organic compounds (VOCs) may be a potential odor concern following land application. This study was conducted to evaluate the effects of land application method, diet, soil moisture content, and time since manure application on VOC emissions. Manure was collected from feedlot pens where cattle were fed diets containing 0, 10, or 30% wet distillers grains. Land application methods included surface-applying manure (i.e., no-tillage) or incorporating manure using disc tillage. The effects of soil moisture content on VOC emissions were determined by adding water to the experimental plots soon after manure application. An assessment of the relative impact of each individual odor compound is provided by odor activity values (OAVs). Volatile fatty acids with notable contributions to total OAV included heptanoic, hexanoic, isobutyric, and isovleric acid with contributions of 23.5, 17.6, 9.26, and 3.39%, respectively. The aromatics, indole and skatole, contributed 9.50 and 5.68%, respectively, to the total OAV. Dimethyl disulfide (DMDS) provided 9.50% and dimethyl trisulfide (DMTS) contributed 5.68% to total OAV. Emissions of the sulfur compounds, DMDS and DMTS, were substantially larger for the 30% WDGS diet. Flux measurements from the no-till plots were generally greater than from the tilled plots. Emissions of VOC were greater the first day following manure addition when wet soil moisture conditions were present. The occurrence of rainfall following manure application influences the types and amounts of VOC which are emitted.

Technical Abstract: Emission of volatile organic compounds (VOCs) may be a potential odor concern following land application. This study was conducted to evaluate the effects of land application method, diet, soil moisture content, and time since manure application on VOC emissions. Manure was collected from feedlot pens where cattle were fed diets containing 0, 10, or 30% wet distillers grains with solubles (WDGS). Land application methods included surface-applying manure (i.e., no-tillage) or incorporating manure using disc tillage. The effects of soil moisture content on VOC emissions were determined by adding water to the experimental plots soon after manure application. Volatile fatty acids with notable contributions to total odor activity values (OAV) included heptanoic, hexanoic, isobutyric, and isovleric acid with contributions of 23.5, 17.6, 9.26, and 3.39%, respectively. The aromatics, indole and skatole, contributed 9.50 and 5.68%, respectively, to the total OAV. Dimethyl disulfide (DMDS) provided 9.50% and dimethyl trisulfide (DMTS) contributed 5.68% to total OAV. Emissions of the sulfur compounds, DMDS and DMTS, were substantially larger for the 30% WDGS diet. Flux measurements from the no-till plots were generally greater than from the tilled plots. Emissions of isobutyric acid, isovaleric acid, indole, skatole, and DMDS were significantly greater under wet than dry soil moisture conditions. Hour significantly influenced emissions of isobutyric acid and the reading of 0.053 µg m-2 min-1 collected initially was significantly greater than measurements obtained at other times. The occurrence of rainfall following manure application influences the types and amounts of VOC which are emitted.