Lab-Scale Model to Evaluate Odor and Gas Concentrations Emitted by Deep Bedded Pack Manure

This method can help answer key questions related to air quality in livestock facilities including the effect of bedding, humidity, temperature, or amendments that are used in bedded livestock facilities. The main advantage of this technique is that it allows factors to be evaluated in a controlled environment and eliminates less effective treatments before conducting research at commercial-sized facilities. Demonstrating the procedure will be Alan Kruger, a technician from my laboratory.

For simulator chambers, use plastic cylindrical containers that are 0.42 meters tall and 0.38 meters in diameter which match some 10 gallon trash containers. Start with drilling out six one-centimeter holes around the circumference of the container approximately five centimeters from the top. Space the holes out equally.

Then clean out the container and load it with 320 grams of bedding material, followed by 320 grams of fresh cattle feces, and 320 grams of fresh cattle urine. Then stir the mixture together using a five centimeter circumference rod for about 30 seconds. After stirring, wipe the rod clean using an antiseptic disposal wipe or warm soapy water to prevent cross-contamination of microbes.

Then record the final mass of the container’s contents. Next, place the plastic container in the environmental chamber set to an ambient temperature of 18 to 20 degrees Celsius with a dew point of 12 degrees Celsius. Three times a week, perform maintenance on the bedding packs.

For this task, first adjust the pH of thawed urine to 7.4 using sodium hydroxide and keep the urine container capped as often as possible. Next, weigh and record the mass of the bedded pack. Then weigh out 320 grams of thawed cattle feces and 320 grams of thawed urine and add both to the bedded pack.

Once per week, also add 320 grams of fresh bedding. Always stir up the mixture for 30 seconds like when it was initially setup before returning the bedded pack simulator to the environmental chamber. Collect samples from the simulated bedded packs weekly prior to maintenance.

First, measure the distance from the top of the simulated bedded pack to the top of the plastic container holding the simulated bedded pack. Next, push a metal stake about five centimeters into the middle of the bedded pack. Then thread 0.64 centimeter outer diameter tubing through one of the holes at the top of the simulated bedded pack container.

Then inside the simulator, attach a 12.5 centimeter metal stake to the tubing so that the tubing is 1.3 centimeters above the bedded pack surface. Next, place rubber skirts with 22.9 centimeter diameter holes onto the static flux chambers. The skirt functions as a seal.

Place the static flux chambers with skirt onto the bedded pack simulators. Now connect the 0.64 centimeter inert tubing to the flux chambers using inert compression fittings. The flux chamber performs the gas sampling and is controlled by a programmable logic relay that controls the solenoid valves, thus the gas flow.

To finish preparing the setup, use the pump to flush ambient air through the tubing at a rate of five liters per minute for 30 minutes. To take gas measurements, first open the stopcock on the sample line to draw ambient air from the room into the inert sample lines connected to gas sampling manifold. Now program the relay to pull in ambient air and record measurements for 20 minutes.

After 20 minutes, close the stopcock to end the sampling period. Next, program the relay to sample air from the lines connected to the simulators for 20 minutes. Meanwhile, measure the volatile organics in the simulator head space.

First, remove the brass storage cap on a preconditioned, stainless steel sorbent tube. Then attach the sorbent tube onto the inlet port on the flux chamber using flexible rubber tubing and attach the other end of the sorbent tube to a vacuum pump. Then pull air into the sorbent tube from the simulator for five minutes for a total sample volume of 0.375 liters.

Later, turn off the pump and put away the sorbent tube. Immediately before analyzing the sorbent tube on the gas analysis system, replace the brass storage caps with PTFE analytical caps. Then proceed with the analysis of volatile organics according to the text protocol.

This procedure has been used to evaluate the effect of numerous bedding materials in ambient temperature on odor and gas production as well as amendments that can be added to control ammonia emissions. Chemical and physical properties of the bedded packs have been measured in commercial barns as well as in the simulated bedded packs. The procedure produces comparable results to commercial facilities and also has good repeatability amongst the simulated bedded pack studies.

To determine if the protocol was a suitable model to supplement expensive on-farm research trials, air quality data was collected from commercial facilities and simulated bedded packs using the described method and older, labor-intensive methods such as the acid trap method. Overall, the measurements were very similar, supporting the use of the described labor-saving method. After watching this video, you should have a good understanding of how to use this lab-scaled model to study factors affecting air quality and nutrient management in livestock facilities using bedding.

Following this procedure, you can create lab-scaled models to evaluate many different materials, environmental variables, and mitigation treatments that can improve air quality in commercial livestock facilities. The model is dynamic and allows researchers to easily collect useful measurements.