Estimating Ammonia Emissions from Livestock Operations Using Low-Cost, Time-Averaged Concentration Measurements
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For more: http://www.extension.org/67697 Recent regulations on ammonia (NH3) and other gaseous emissions by the EPA requires managers of animal feeding operations (AFOs) to report their annual emissions of greenhouse gases (GHGs), with the possibility of federal funding in the near future to be allocated for enforcement of GHG reporting as well as to levy large fines against AFOs that exceed the regulation limitations for GHG emissions. The current method of estimating NH3 emissions for AFOs is a “back of the envelope” type calculation based upon population and type of animal within an individual AFO.
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Estimating Ammonia Emissions from Livestock Operations Using Low-Cost, Time-Averaged Concentration Measurements
- 1. Kira Shonkwiler and Jay Ham Department of Atmospheric Science, Colorado State University Department of Soil and Crop Sciences, Colorado State University Estimating Ammonia Emissions Using Low-cost, Time-averaged Concentration Measurements
- 2. Objectives • Adapt diffusive NH3 samplers for weather-based conditional sampling • Field test at beef feedlots and dairies • Estimate pen NH3 emissions using an inverse model
- 3. Radiello Diffusive/Passive Samplers • Pros – Widely used for NH3 (e.g., AMoN network) – Inexpensive, Simple • Cons – Cumulative – Conc. affected by wind dir. /speed, stability, … – No Stationarity over sample period www.nescaum.org/documents/mac/ mac-committee...3/rury-amon.pdf/
- 4. Conditional Samplers • Robotic mechanism exposes samplers when a given set of user-defined weather conditions exist – Min. Wind speed – Wind Direction Range – Time of Day, others • Wireless Sensor Net – Synoptic sampling – Xbee
- 5. Actuator Control `` Linear Actcuator Acrylic Tube Cap Spacer Vertical Adapter Radiello Diffusive Sampler Foam Acrylic Disc Hall Effect Sensor Control Cable Spacer Clevis Clevis Plunger Magnet Hall Effect Cable
- 6. Arduino Shield Stacks and Datalogger Module
- 8. Weather-Based Sampling Under automated control, samplers were exposed to the air for a total of 3.5 to 4 days during a 14 day sampling period.
- 9. Field Testing: Feedlot Feedlot 25,000 Head 700 m North South West Lot Base Pasture Prevailing Wind
- 10. Average concentration for each deployment (Oct 2012 – Feb 2013)
- 11. Inverse Modeling Know average concentration, wind characteristics, and site layout… Can infer emissions Inverse Model Weather Data Source Geometry and Roughness Concentration Data Emissions
- 12. FIDES Flux Interpretation by Dispersion Exchange over Short-range (FIDES) Inverse model (inputs: u* and L) Solves the advection-dispersion equation Uses concentration ( ) from a location (x, z) to estimate source strength of a different location (xs, zs) Loubet et al., 2001; 2010 Cbgd is the constant background concentration S is the source strength D is a dispersion function
- 13. FIDES Applied successfully in Europe (Loubet et al., 2001; 2009; 2010) NH3 concentrations measured with high-speed instrumentation Work at CSU is first attempt at modeling NH3 emissions from time-averaged data (i.e., the conditional passive samplers)
- 15. Model Output – Emissions Average emissions for each deployment cycle (Oct 2012 – Feb 2013) Decrease in volatilization from surface during winter
- 16. Average temperature (above) and wind speed (below) for each deployment period. Temperatures during the 2012 – 2013 winter (green line) were much higher than the 15-year normal (red line) Mean wind speeds varied little over each period
- 17. Model Output – Emissions Histogram (frequency distribution) of output emissions from FIDES Log-normal distribution, 92% of values fall between 20 – 100 g m-2 s-1
- 18. Model Output – Emissions Emissions summary Average Emissions: 4.7 g m-2 d-1; 96.5 g head-1 d-1 Percent of Fed-Nitrogen emitted as NH3 averaged 53%
- 19. Conclusions Emissions decreased throughout the winter as temperature decreased Predicted emissions have a log-normal distribution Average model output was 20 – 100 g m-2 s-1 Emissions averaged 96.5 g head-1 d-1 and 4.7 g m-2 d-1 53% of Fed N emitted to air as NH3 Next steps Compare to continuous NH3 measurements (e.g., boreal laser Todd et al., 2008; mobile sampling)
Editor's Notes
- Point out that an inverse model is different from a backwards lagrangian stochastic model
- The North site was always higher, the cows were younger in this pen, and the pen was smaller (feed younger cattle more N)
- Put the temperature data here, compare to historical average
- % Fed N compare well to the work done by Rick Todd and Andy Cole, stocking rate = 20.5 m2, 8.8 % fed N to the bunk (180.4 g/head)We only used a few pens around the samplers to calculate the emissions factorsCrude protein in the diet, ~13%
- Saw spatial variability in model output; next steps section – compare to boreal laser (Todd et al, 2008)