Ammonia Air Pollution: Strategies For Control And Management

Ammonia (NH3) is a major air pollutant that poses significant risks to both human health and the environment. Sources of atmospheric ammonia include agricultural practices, such as livestock operations and the use of nitrogen fertilisers, as well as non-agricultural sources like municipal waste treatment plants and industrial combustion processes. Ammonia emissions contribute to the formation of fine particulate matter (PM2.5), which has been linked to respiratory illnesses, reduced lung function, and even premature mortality. The impact of ammonia pollution is not limited to air quality but also extends to ecosystems, causing soil acidification, promoting certain plant communities over others, and leading to water eutrophication, which can have cascading effects throughout the entire ecosystem. With its ability to react with other chemicals and travel long distances, ammonia also contributes to international transboundary air pollution issues. As concerns about ammonia emissions grow, regulatory and policy discussions are increasingly focusing on mitigating its environmental and health impacts. This includes developing best management practices to reduce ammonia emissions and protect natural resources for future generations.

How to Control Ammonia Air Pollution

Reducing ammonia emissions from agriculture

Agriculture is a significant contributor to ammonia emissions. Here are some ways to reduce ammonia emissions from agriculture:

Feed Management

The feed composition and feed management have a strong influence on ammonia emissions. By ensuring that farm animals are not fed more protein than is necessary, N excretion can be reduced. This can be achieved through better adaptation of the feed composition to the needs of the animal, such as adjusting the amount of protein according to the animal's lactation stage, age, and weight. Properly balanced protein feeding can also reduce ammonia production from slurry, as less nitrogen will be excreted.

Manure Management

Ammonia emissions from slurry can be reduced by minimising the exposed surface area of slurry or liquid manure in storage. This can be done by covering slurry pits and silos with a roof, a floating cover, or floating bodies such as plastic, straw, or bark. Additionally, immediate incorporation of manure within a few minutes can avoid up to 90% of ammonia losses. Diluting slurry by at least 50% at low temperatures through irrigation systems can also help reduce emissions. Acidifying the slurry to a neutral level or a pH value of 6 can reduce outgassing of ammonia by at least 50%.

Fertiliser Management

Urea-based fertilisers are vulnerable to volatilisation, releasing ammonia into the atmosphere. Switching to ammonium nitrate, which has lower emissions, or using urea fertiliser treated with a urease inhibitor, can help reduce emissions. Injecting liquid urea into the soil or incorporating it immediately after application can also reduce ammonia losses. Field irrigation following fertilisation helps prevent nitrogen losses by "washing" the fertiliser into the soil.

Slurry Spreading

When spreading slurry, shallow injection can reduce ammonia emissions by up to 70%. Choosing cooler and less windy weather conditions for slurry spreading can also help reduce emissions. Incorporating surface-spread slurry into the soil as soon as possible, ideally within 12 hours, retains more of the nitrogen content and makes it available to crops.

Housing and Storage Systems

The UN Economic Commission for Europe's Framework Code of Agricultural Practice provides guidance on housing and storage systems to reduce ammonia emissions. Implementing these recommended practices can help reduce emissions at the farm level.

Regulating ammonia as a precursor to PM2.5

Ammonia is a key contributor to air pollution, particularly in agricultural areas. It is produced when urea in urine is broken down by the enzyme urease, which is present in feces and soil. This process releases ammonia gas and carbamine acid, which further decomposes to produce another molecule of ammonia gas and carbon dioxide. The gas, when not blown aloft, has a short atmospheric lifetime, usually depositing near its source via wet or dry deposition in rain, snow, or otherwise. However, when ammonia gas reacts with other chemicals and transforms into particles, it can travel further and last longer in the atmosphere.

Gaseous ammonia can react with nitric and sulfuric acids, which are formed from NOx and SOx, respectively, through industrial and vehicle combustion processes. These reactions result in the formation of solid ammoniated particles, such as ammonium nitrate and ammonium sulfate, which contribute to fine particulate matter, or PM2.5. PM2.5 is a term used to describe particulate matter that is 2.5 microns in diameter or smaller. Due to its minuscule size, PM2.5 can penetrate the natural barriers in our respiratory system, lodging deep inside our lungs and causing adverse health effects.

Similarly, in Utah, researchers from USU, BYU, and the University of Utah have collaborated on the WaFACO study to monitor and locate sources of ammonia along the Wasatch Front. This data will inform pollution control strategies to protect public health in the region. The Utah Winter Fine Particulate Study (UWFPS) in 2017 also highlighted the significant role of ammonia in wintertime PM2.5 in the Salt Lake Valley, with ammonium nitrate accounting for up to 70% of total PM2.5 during periods of federal standard exceedances.

To effectively regulate ammonia as a precursor to PM2.5, a comprehensive understanding of the chemical and physical processes involved is necessary. This includes recognizing the impact of factors such as temperature, relative humidity, and hygroscopic water on PM2.5 concentrations. By identifying the sources and mechanisms of ammonia emissions, targeted abatement strategies can be developed to reduce atmospheric particulate matter and improve air quality, thereby safeguarding public health and the environment.

Managing livestock operations

To effectively manage livestock operations and reduce ammonia emissions, several strategies can be implemented:

• Livestock Feed Management: The amount of nitrogen (N) in animal feed directly influences the levels of N excreted in faeces and urine. By reducing the protein content in livestock diets, emissions can be lowered. For instance, crude protein levels in dry matter for dairy and beef cattle should be maintained at around 16% and 12%, respectively, to achieve noticeable reductions in N emissions.
• Animal Housing and Manure Storage: Proper management of animal housing and manure storage facilities is crucial. Acidification of manure with additives like phosphoric acid (H3PO4) and sulfuric acid (H2SO4) can reduce ammonia volatility by inhibiting the activity of microbes that convert nitrogenous compounds to ammonia. Additionally, planting a buffer strip of trees or tall grasses downwind and around housing and storage areas can help capture ammonia before it escapes into the atmosphere.
• Manure Spreading and Land Application: The application of manure to land is a significant source of ammonia emissions. Different methods of manure application, such as tine injection, disc injection, and immediate incorporation, can reduce ammonia losses. Sampling manure for nutrient content prior to land application ensures the provision of appropriate nutrients for plant growth while minimising ammonia emissions.
• Technological Interventions: While some interventions may be beyond the scope of small farm operations, adopting appropriate technology or infrastructure can significantly reduce ammonia emissions. This includes investing in manure and exhaust air treatment technologies, which are particularly relevant for sustainable intensive livestock production systems.

It is important to note that even small adjustments to existing management practices can contribute to positive outcomes in ammonia emission reduction. These changes not only benefit the environment and human health but also enhance farm business efficiency by conserving valuable resources and reducing financial losses associated with increased fertiliser costs.

Controlling municipal waste treatment plants

Municipal waste treatment plants are responsible for processing domestic waste and must comply with permit limits to protect waterbodies from pollutants such as ammonia. However, during storms or treatment plant failures, there is a risk of high ammonia releases into streams and lakes. To control ammonia air pollution in these settings, several methods can be employed:

Preventative Measures

The first step is to prevent excess ammonia production. This can be achieved by minimising the contact between urine and faeces, as urea in urine breaks down into ammonia gas when it comes into contact with urease in faeces.

Treatment Methods

When it comes to treating the ammonia that has already been produced, there are several methods available:

• Air Stripping: This is one of the most widely used methods for removing ammonia from wastewater. It involves passing air through the wastewater to strip away the ammonia.
• Ion Exchange: This method utilises minerals like granular activated carbon, natural zeolite, and sodium activation to remove ammonium ions from wastewater.
• Breakpoint Chlorination: Chlorination is a treatment option that can be considered for ammonia removal.
• Biological Nitrification-Denitrification: This biological process is another commonly used method for treating wastewater and removing ammonia.
• Concentration Methods: Techniques such as flocculation, precipitation, ultrafiltration, nanofiltration, reverse osmosis, and evaporation can be used to concentrate and separate ammonia from wastewater.

Regulatory Compliance

It is important to comply with permit limits and regulations designed to protect waterbodies from excess ammonia inputs. Regularly reviewing and adhering to federal and state policies focusing on air quality concerns from agricultural sources is crucial.

Research and Innovation

Continued research and innovation in ammonia removal techniques are essential. For example, a study on the removal of ammonia from municipal waste treatment effluents using natural minerals showed promising results with various commercial minerals.

Understanding the impact of ammonia on human health

Ammonia is corrosive and can have severe impacts on human health. The severity of the health effects depends on the route of exposure, the dose, and the duration of exposure. It is produced in the human body and is commonly found in nature. It is essential in the body as a building block for making proteins and other complex molecules. In nature, ammonia occurs in soil from bacterial processes and is also produced when plants, animals, and animal wastes decay.

Ammonia is also widely produced in the United States, where about 80% of the ammonia produced is used in agriculture as fertilizer. It is also used as a refrigerant gas, to purify water supplies, and in the manufacture of plastics, explosives, fabrics, pesticides, dyes, and other chemicals. It is found in many household and industrial-strength cleaning solutions.

Ammonia is a colorless, highly irritating gas with a sharp suffocating odor. It dissolves easily in water to form ammonium hydroxide solution, which can cause irritation and burns. Exposure to high concentrations of ammonia in the air causes immediate burning of the eyes, nose, throat, and respiratory tract and can result in blindness, lung damage, or even death. Inhalation of lower concentrations can cause coughing, and nose and throat irritation. The widespread use of ammonia on farms and in industrial and commercial locations means that exposure can also occur from an accidental release or from a deliberate terrorist attack.

Ammonia gas is lighter than air and will rise, so it generally does not settle in low-lying areas. However, in the presence of moisture, ammonia can form vapors that are heavier than air. When in gaseous form and not blown aloft, ammonia has a short atmospheric lifetime of only a few hours and usually will deposit near its source via wet deposition in rain and snow, or dry deposition. Gaseous ammonia can travel further and last longer in the atmosphere if it reacts with other chemicals and is transformed into a particle.

Ammonia toxicity occurs when susceptible individuals suffer exposure to external sources of ammonia via ingestion, inhalation, direct contact with skin, or contact with the eyes. It presents similar to other caustic substance ingestions, with acute onset eye pain and irritation. Ingestion of ammonia-containing cleaners occurs predominantly in children and is accidental. However, 9.2% of household exposures are intentional and occur mostly in adults.

Frequently asked questions