Chayan Kumer Saha

Seasonal and diel variations of ammonia and methane emissions from a naturally ventilated dairy building and the associated factors influencing emissions

Understanding seasonal and diel variations of ammonia (NH3) and methane (CH4) emissions from a naturally ventilated dairy (NVD) building may lead to develop successful control strategies for reducing emissions throughout the year. The main objective of this study was to quantify seasonal and diel variations of NH3 and CH4 emissions together with associated factors influencing emissions. Measurements were carried out with identical experimental set-up to cover three winter, spring and summer seasons, and two autumn seasons in the years 2010, 2011, and 2012. The data from 2010 and 2011 were used for developing emission prediction models and the data from 2012 were used for model validation. The results showed that NH3 emission varied seasonally following outside temperature whereas CH4 emission did not show clear seasonal trend. Diel variation of CH4 emission was less pronounced than NH3. The average NH3 and CH4 emissions between 6a.m. and 6p.m. were 66% and 33% higher than the average NH3 and CH4 emissions between 6p.m. and 6a.m., respectively for all seasons. The significant relationships (P<0.0001) between NH3 and influencing factors were found including outside temperature, humidity, wind speed and direction, hour of the day and day of the year. The significant effect (P<0.0001) of climate factors, hours of the day and days of the year on CH4 emission might be directly related to activities of the cows.

Modeling Ammonia Mass Transfer Process from a Model Pig House Based on Ventilation Characteristics

Airflow characteristics above the emission surface inside animal houses play an important role in gaseous and odor emissions. The influence of airflow characteristics, i.e., air velocities and turbulence intensities, on ammonia mass transfer processes were investigated in a model of a finishing pig house. The 1:6 scale model was 1750 × 1000 × 605 mm (L × W × H) and had two sidewall inlets and an exhaust opening in the middle of the ceiling. Different airflow characteristics were generated by using three ventilation control strategies: constant inlet opening area, constant inlet velocity, and constant inlet momentum. Due to the symmetrical nature of the airflow pattern in the scale model, the investigation was conducted in left half of the model. Nonlinear modeling simulated the ammonia mass transfer coefficient (AMTC) as a function of airflow characteristics and jet momentum number. Changes in ventilation control strategies, given the variation of floor air characteristics, changed the ammonia emissions and AMTC. The mean floor air velocities and the root mean square of the floor air velocity fluctuations were correlated to the jet momentum number to the power of 0.56 and 0.54, respectively. AMTC increased proportionally to floor air velocity and turbulence intensity. The AMTC values determined in this experiment were compared to a published study using a 1:12.5 scale model. The correlation of AMTC and jet momentum number for the two models was similar. The relationships obtained in this study could be helpful in understanding the airflow characteristics in the floor region and simulating emission rates from pig houses, while the dependence of AMTC on jet momentum number was confirmed for two different scale models. There is a need to validate it in full-scale houses since the presence of pigs, slatted floors, and porous partitions could alter the relationship of jet momentum number with AMTC.

Windkanaluntersuchungen an einem frei gelüfteten Milchviehstall

The air exchange rate regulating the climate inside of natural ventilated livestock buildings is hard to determine in the field due to the variability of time and space of the dominant processes. Experiments in a wind tunnel laboratory can produce sound statistical and representative data obtained under controlled boundary conditions to complete data sets from the field. In this study, measurements of the horizontal wind components within a model of a natural ventilated barn were performed in the wind tunnel. The approach flow was chosen with low turbulence in order to gain knowledge on the influence of the installed equipment on the air flow. In fact, the measured profiles were influenced by the installed equipment and the feeding alley.