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Controlling ammonia emissions in finishing barns

Learn how ammonia emissions negatively impact pig performance and how to mitigate them

The most common complaint producers hear when people drive past or visit a pig barn is the smell. Ammonia, a gas released when manure decomposes, can be easily recognized by its pungent odor. Ammonia can be detrimental to the health and welfare of animals and employees, when at low concentrations. Livestock production is responsible for almost 64% (Dopelt et al., 2019) of global ammonia emissions. The global swine industry is responsible for about 15% of ammonia emissions associated with livestock. The swine industry’s contribution varies by region due to the concentration of animals and can be as high as 60% in areas of China and 25% in Europe (Olivier et al., 1998; Philippe et al., 2011; Xu et al., 2014).

Considering the scenario, many swine producers must ask: how can we control ammonia in grow-finish operations? First, it’s necessary to understand where ammonia originates. In swine operations, ammonia is a byproduct of microbial decomposition of urine and feces in the manure storage pit below the floor.

A simple explanation for this complex process is:

  • Urea, from urine, is converted to ammonia and carbon dioxide by the microbial enzyme urease (from microbes excreted in feces).
  • Once formed, free ammonia can take two forms, depending on the pH of the manure: NH3 (ammonia) or the ammonium ion (NH4+)
  • At low pH, most of the ammonia remains in the liquid as NH4+
  • At pH greater than 7, the ammonium ion is converted to ammonia (NH3) and can escape as gas.




Strategies to control ammonia production

Ammonia volatilization is a process that depends on many factors such as relative humidity, animal density and activity, amount of manure and urine on the floor, airspeed in the building, and dry matter content in the manure (Blanes-Vidal et al., 2008; Fabbri et al., 2007). Throughout all stages of pig production, ammonia production is a concern, but most specifically in grow-finish operations, which account for 60-70% of the total nitrogen excretion (Jongbloed and Lenis, 1993). Considering the above, efforts to reduce ammonia production are necessary.

Environmental and nutritional management practices are necessary to reduce ammonia levels in pig production significantly. Environment control, especially ventilation, is one strategy to reduce ammonia emissions. According to Tabase et al. (2018), managing the NH3 emission from livestock buildings requires introducing fresh air into the units while avoiding over-ventilation above the manure-covered surfaces. Another way of introducing fresh air is to adjust inlet openings, promoting constant airflow into the building. Biofilters and scrubbers can also be used in mechanically ventilated systems, as they encourage air purification.

Manure management is also crucial when it comes to reducing ammonia emissions. Removal of manure is recommended 1-2 times per day from pig stalls. Storing manure for an extended period increases ammonia production within a facility. For example, a storage period of 3 days can result in a 40% increase in NH3 (Botermans et al., 2010) Therefore, under ideal circumstances emptying the pit frequently is advised. Additionally, methods for reducing microbial activity in manure may be helpful, such as using additives to lower the pH.

Pen design and hygiene are also essential factors to consider. Cleaning the slats the lying area should be the primary objective. Botermans et al. (2010) suggested a slope with an incline between 2% and 3% on the floor to help drain uring. Furthermore, the excretion area should account for at least 25% of the lying area. Keeping pigs clean and dry is also critical, especially in the summer, when heat-stressed animals change their behavior and start lying on the slatted floor.

Dietary manipulation can also aid in the control of ammonia emissions by minimizing the crude protein level within the diet. Le et al. (2009) demonstrated that reducing crude protein in pig diets can significantly reduce ammonia emission from manure. Portejoie et al (2014) reported that dietary protein reduction from 20% to 12% resulted in a 63% reduction of ammonia emissions.


How does ammonia affect grow-finish operations without proper control?

The negative impact of ammonia emissions goes far beyond its irritating odor. High concentrations of ammonia are detrimental to the health of both pigs and the people working in the facilities. Ammonia levels of 7 ppm can reduce pulmonary function in swine farm workers (Donham et al., 1989; Donham et al., 1995), and concentrations above 35 ppm promote inflammatory changes in the wall of the respiratory tract and reduce bacterial clearance from lungs in young pigs (Drummond et al., 1978). High levels of ammonia within the barn can also cause an increase in pig restless, and ear, tail, and flank biting. In addition, ammonia concentrations of 50 ppm or above can cause inflammation of the respiratory tract, increasing susceptibility to respiratory infections by reducing the rate of bacterial clearance (Gustin et al., 1994; Urbain et al., 1994). High levels also affect animal performance, reducing growth rates up to 12% during prolonged periods of exposure (Drummond et al., 1980).



Ammonia emission is a constant challenge for all swine producers since high concentrations of this gas have harmful effects on pig health and performance. This article has provided an overview of ammonia volatilization, how grow-finish pigs are affected, and practical strategies for reducing its concentration in swine building. If a single ammonia mitigation method doesn’t work, farms should consider using several approaches to control ammonia in grom-finishing operations.

Find more information at protekta.com for ammonia mitigation solutions, including Stalosan F: a valuable tool when it comes to ammonia control. Stalosan F acts as a buffer that chemically controls manure moisture and pH. Furthermore, Stalsoan F inhibits urease enzyme activity, decreasing the conversion of urea to ammonia.



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