manure agitating

Good time of year for pit pumping pointers

During agitation and pumping, noxious gases are released from the slurry and can rapidly spike at any time and at any location. Failure to keep gas concentrations at safe levels can result in a dangerous situation for everyone.

By Brett C. Ramirez and Daniel Andersen, Iowa State University Department of Agricultural and Biosystems Engineering
Pit pumping in late-January? Probably not, but rather than hearing the common best safety strategies during the fall when you expect it, now is a good time to drive home and reflect on the strategies to keep you, others around you and the pigs safe.

As many of us all know, during agitation and pumping, noxious gases are released from the slurry and can rapidly spike at any time and at any location. Failure to keep gas concentrations at safe levels can result in a dangerous situation for everyone. This column will repeat much of the information (Iowa State Extension Store) on pumping safety, but it never hurts to hear something twice.

The four main gases to be concerned about are hydrogen sulfide, ammonia, methane and carbon dioxide. Let’s start with H2S because it’s the most dangerous — it’s heavier than air; that means it will pool at the pit surface or in corners where air is stagnate and is characterized by a rotten egg smell. It’s a big concern because even at low concentrations, it can quickly desensitize your smell, such that you cannot detect higher gas concentration levels.

Ammonia, characterized by its sharp odor, is also heavier than air and can cause eyes to burn or water. Methane, which is lighter than air, is primarily a concern because at high concentrations (>50,000 parts per million) it can become explosive (bad in a barn, good in an anaerobic digester). Lastly, CO2 is an odorless gas that can cause asphyxiation if enough oxygen is displaced.

Luckily, monitors exist to measure a single gas or combinations of all these gases. When shopping for a monitor, pay attention to if it performs as just an alarm or as a real-time monitor. An alarm will provide some audio and/or visual feedback to alert the user if concentrations are above a threshold, but doesn’t indicate the current concentration. The benefit of the slightly more expensive real-time monitor is that current gas concentrations are displayed on the screen and the operator can make informed decisions on what agitation practices need to be modified.

During agitation, it is important to be mindful of where some of these high gas concentrations can occur. One is directly over pump-out, inside the building, or directly downstream of the exhaust fans. Pump-out openings can act like inlets, with the exhaust fans running they pull air through the opening, picking up the noxious gases over the slurry, and bring them directly into the animal zone. This is where a pump-out curtain can be very helpful in sealing the pump-out opening. Just remember when you are walking or driving around the facility, be cautious about lingering and being directly in the path of the exhaust fans.

We are not going to get into detail on the best agitation strategies, but will briefly mention some of the important ones. Do not agitate until the manure level is 1.5 to 2 feet below the slats and avoid aggressive agitation when animals are in the building (no “rooster tailing”). Do not direct agitator nozzles toward pillars, walls or toward a corner, and stop agitating when bottom nozzle is less than 6 inches below the manure surface.

Key safe operation procedures: Never enter the building while pumping — use caution tape, mark barn entrances and alert everyone that pumping is occurring. If possible, remove animals from the portion of the barn where agitation and removal is occurring. It may be worth investing in a gas monitor, if you have one, have it handy during pumping. Make sure someone is at the site during pumping and they have a copy of the emergency action plan. Prohibit smoking, open flames or spark-producing activities in the immediate vicinity. Observe animals for signs of noxious gas distress.

Now briefly onto ventilation strategies broken down by ventilation system type and weather. Main things for curtain-sided barns during warm weather: need a wind greater than 5 mph (perpendicular to barn) or at least 7.5 to 10 mph wind when the wind is at an angle. Keep sidewall curtains open and exhaust fans on. If wind is less than 5 mph, make sure all exhaust fans are on with sidewall curtains closed. If more than 50% of pit fans are removed for pumping and agitation, curtains should remain open regardless of wind speed. During cold weather, maximum mechanical ventilation for big pigs and a minimum of 25-30 CFM per pig of mechanical ventilation for small pigs. Reduce static pressure by opening ceiling inlets fully and dropping the curtain slightly.

Main things for tunnel-ventilated barns during warm weather: operate all pit fans and at least two large (36 inches) tunnel fans with the tunnel curtain open to 6 to 12 inches (300 to 400 FPM air speed is desired at the curtain inlet). Ceiling inlets should be partially closed if powered, to force air through end-wall curtain. During cold weather, run all pit fans and at least one 36-inch fan with the tunnel curtain open to 6-12 inches (again, 300 to 400 FPM air speed is desired at the curtain inlet). For both warm and cold weather, continue elevated ventilation for at least two hours after pumping stops. Regardless of barn type, stir fans should be used parallel to air flow to move air.

While many of you have attended countless presentations and received the fact sheets, listening or reading safety information and best practices in a different context is in your best interest.

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