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Estimation of Emission Uncertainty from a Broiler Building Using Numerical Methods

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1008955.(doi:10.13031/2013.29772)
Authors:   Salvador Calvet, Fernando Estellés, María Cambra-López, Antonio Germán Torres
Keywords:   Uncertainty, gas emission, animal house, ventilation

The report of an emission rate must include an estimation of the measurement error in the results. In this work the uncertainty in the ammonia emission rates was evaluated using numerical methods (Monte Carlo methods), which constitute a robust methodology to propagate uncertainties. The main objectives were to define properly the influencing variables, to study the contribution of these variables, and to account for the existing dependence between variables, particularly gas concentrations and ventilation flows. Ammonia emissions and ventilation flows were simultaneously measured for one growing period in a commercial broiler facility. Emission rates and their uncertainties were calculated for days 30 and 31 of the growing cycle. Ventilation flow uncertainty was estimated from a previous study, whereas uncertainty in gas concentrations was originated on the instrument calibration and the sampling on the farm, and was specifically obtained for this study. Ammonia emission rates ranged from 18.58 to 76.80 mg per animal and hour. The gas concentration error depended on the measured value, and was characterized for the measurement system used in this study. The correlation coefficient between gas concentrations difference and ventilation rate over a growing cycle was -0.62. The contribution of gas concentration to the overall emission rate uncertainty was 63%, whereas the ventilation flow contributed by 37%. Finally, if correlations were considered, the emission rate uncertainty decreased. However, this correlation must not be included in the uncertainty if the errors of gas concentration and ventilation flows are independent, despite both variables are correlated by cause and effect.

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