For centuries farmers have used chicken manure as garden fertilizer. Chicken manure is particularly high in nitrogen as well as potassium and phosphorus, the three most important elements in all man-made and organic fertilizers used today.
When you see 3 numbers like 12-8-6 on a bag of fertilizer, the NPK ratio is 12% nitrogen (N), 8% phosphorus (P) and 6% potassium (K). The dozen other micronutrients needed by plants can be found in the soil.
While the positive impact of fertilizer on our abundance of food is undeniable, the increasing world-wide production of poultry has created a corresponding increase in chicken manure which is high in ammonia. When not properly disposed of
- Excess ammonia is dangerous to the birds and those who care for them.
- Ammonia gas drifting downwind is an irritant to neighbors.
- Spread on nearby land, areas around poultry farms contain too much nitrogen in the soil. While this is good for plants, excess nitrogen is especially harmful if it migrates into the nearby lakes and streams.
As a result, the massive growth of this industry has lead scientists to investigate the impact of poultry farming on the environment.
The Nitrogen-Chicken Connection
Nitrogen is part of a normal chicken’s diet from proteins and other sources. While some of it is used to for growth or to lay eggs, most of it leaves the chicken in the form of the compounds uric acid (80%), ammonia (~10%) and urea (~5%). The uric acid and urea are converted into additional ammonia by bacteria and enzymes.
As the ammonia decomposes it returns to its natural chemical state of nitrogen and hydrogen. Fresh chicken manure contains 0.5-0.9% nitrogen, 0.4-0.5% phosphorus, and 1.2-1.7 % potassium. One chicken produces approximately 8–11 pounds of manure monthly.
According to a study published in the journal Science of the Total Environment, poultry litter from 600 poultry houses around Chesapeake Bay produced 33.8 million pounds of ammonia per year and 22.4 million pounds of that ammonia was dumped in the nearby area. As a result the study estimates that about 25% of the nitrogen pollution entering the bay is the result of nearby poultry farms.
Excess ammonia in poultry farms has several impacts:
- Ammonia gas exposed to moisture creates ammonium, which is harmful to the birds as well as farm workers. The exposure levels for ammonia is set to 20-25ppm in many countries. However, in practice, the concentration of ammonia in some broiler houses may easily exceed 30-70 ppm.
- As ammonia in the soil breaks down into its constituent molecules nitrogen and hydrogen, it can be hazardous to the watershed. While nitrogen is not toxic, when combined with hydrogen to form ammonia (NH3) it is hazardous to the environment. Ammonia makes soil more acidic, and as it breaks down can cause excessive richness of the nutrient nitrogen in lakes and streams. This leads to dense plant growth which can kill water-dwelling animals and fish from lack of oxygen.
- Nitrogen from poultry farms also lead to poor water quality. Nitrogen combined with hydrogen produce ammonia in the birds digestive system. As the ammonia is released it breaks down and liberates the nitrogen which acts as a nutrient to feed algae growth. These algae blooms create low-oxygen “dead zones” in nearby lakes.
Ammonia Abatement Solutions
Reducing the ammonia in chicken manure is shown to reduce the nitrogen footprint. Chicken farmers are encouraged to use a combination of strategies.
Diet management. A proper diet lessens the amount of wet manure. Wet manure not only contains more ammonia, but when combined with moisture releases the ammonia gas. This is not only bad for the bird’s health, but causes obnoxious odors in the surrounding areas.
Optimized stock density. Too many birds in a small area create high levels of ammonia leading to decreased bird growth, increased sickness and death.
Optimize heating, cooling and ventilation. The impact of ammonia gas on poultry can be lessened by increased ventilation. The tradeoff faced by poultry farmers is that better ventilation requires more energy either as fans or as heaters.
Chemical additives. A study hosted by the USDA Agricultural Research Service suggested that the use of aluminum sulfate (Alum) in poultry litter was shown to reduce ammonia emissions. Other studies have suggested sodium bisulfate having the same effect. These chemicals are currently marketed to poultry farmers.
Measuring Ammonia
In the US, maximum levels of ammonia in chicken houses is set at 25 ppm by the National Institute of Occupational Safety and Health (NIOSH) and 50 ppm by the Occupational Safety and Health Administration (OSHA). These 8-hour exposure levels are based on human safety. However, people can smell ammonia at concentrations of 20-30 ppm.
While there are electrochemical sensors specifically designed to measure ammonia in air, a new type of sensor using a Molecular Property Spectrometer is now available that can measure ammonia along with other flammable gasses. For example, the latest generation of flammable gas sensors by Nevada Nano can accurately report 0-100% LEL over a dozen different gases.
Photo by Artem Beliaikin from Pexels