Location: Soil, Water & Air Resources Research
Project Number: 5030-11610-006-012-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 3, 2024
End Date: Aug 31, 2031
Objective:
The overarching goals of the Ames group are (1) to measure baseline emissions from swine finishing barns with deep-pit manure storage, external in-ground manure slurry storage, and emissions from composting of mortalities; and (2) identify strategies (methods and techniques) to reduce CH4, NH3, and N2O emissions.
1. Determine emissions baseline of methane (CH4), ammonia (NH3), and nitrous oxide (N2O) from a swine finishing barn with a deep-pit manure storage system.
2. Evaluate various strategies to reduce CH4 and NH3 emissions in deep-pit manure storage, such as acidification, frequent pumping, and micro-aeration.
3. Determine emissions baseline of CH4, NH3, and N2O from a swine finishing barn with external in-ground swine manure slurry storage.
4. Evaluate various strategies to reduce CH4, NH3, and N2O emissions from in-ground swine manure slurry storage such as acidification, frequent pumping, permeable covers, and micro-aeration.
5. Determine and compare emissions of CH4, NH3, and N2O from composting of mortalities using traditional static piles/bins, forced aeration, rotating drums, etc.
Approach:
For Objective 1 and 2, tunnel-ventilated barns with deep-pit manure storage will be used for estimating barn gas emissions. Gas concentrations will be measured for approximately one week at predetermined time intervals to include initial barn conditions (i.e., no animals) and within two weeks of the end of each feeding phase of the swine grow cycle. Concentrations of NH3 and CH4 will be measured using tunable diode lasers (TDL) for whole barn integrated average concentration and emission calculations. A cavity ring-down spectrometer (CRDS) for NH3, CH4, N2O, and CO2 will be used to measure N2O concentrations in the barn and be used in emission calculations.
Barn emission calculations for individual gases will be based on the barn ventilation rates at a given time multiplied by the net (indoor air concentration minus the ambient air concentration) air concentration for a given compound. Barn ventilation will be based on the calibration of individual fans and the fan program (i.e., ventilation “stage”) used in each barn ventilation system. Barn fans will be calibrated at the beginning and end of the study using a Fan Assessment Numeration System (FANS Unit) from the Cooperator.
For Objectives 3 and 4, the open-source in-ground swine manure slurry storage, upwind air will be monitored continuously during intensive measurement campaigns using NH3 and CH4 TDL and N2O samples will be taken at locations of dominate fetch during sampling. Air from the slurry store will be monitored at locations above the surface close to the center or at the downwind side of the slurry store based on wind patterns using NH3 and CH4 TDL and for N2O CRDS. Depending on the availability open-path Fourier Transform Infrared (FT-IR) spectrometers may also be used to estimate field gas concentrations.
In-ground swine manure slurry storage emissions for NH3, CH4, and N2O will be calculated from differences in upwind and downwind concentrations using Windtrax software. A mobile meteorological station will collect air temperature, wind direction, wind speed, and barometric pressure during the experimental period.
For Objective 5, static piles/bins, forced air chambers, and rotary drum gas concentrations will be measured using a CRDS for NH3, CH4, N2O, and CO2. Smart portable soil gas chambers and/or EPA soil flux chambers will be used to estimate emission fluxes from compost static piles/bins. Forced aeration will estimate fluxes based on the ventilation rates of the sample bag chambers. If the facility footprint is large enough, open-path gas measurement using TDL or FT-IR will be used to measure gas concentrations and emissions calculated using Windtrax software with accompanying micrometeorological data collected.
