Agricultural Air Pollution: Activities To Watch Out For

Agriculture is a major source of air pollution, with emissions from farms outpacing all other human sources of fine-particulate air pollution in much of the United States, Europe, Russia, and China. The use of pesticides and fertilizers, diesel emissions, and livestock waste are some of the agricultural activities that contribute to air pollution. These activities release harmful gases such as ammonia, methane, nitrogen oxides, and carbon dioxide, which can have detrimental effects on human health and the environment.

Use of pesticides and fertilizers

Agriculture is responsible for 92% of volatile ammonia emissions (NH3). The use of nitrogen fertilizers alone contributes to 17% of these emissions. Nitrogen oxide (NO) and nitrogen dioxide (NO2) are major sources of pollution in the US and worldwide, and nitrogen-based fertilizers are a significant source of these gases. While the California Air Resources Board (CARB) reports that only 3.8% of NOx air pollution comes from croplands, researchers from the University of California, Davis, have found that the number may be as high as 20 to 51%.

Nitrogen-based fertilizers are applied in a form that plants can readily use. However, when plants do not immediately absorb these fertilizers, they can cause pollution problems. In addition, excess fertilizers wash off fields and pollute watersheds. For example, each summer, an oxygenless "dead zone" spreads from the mouth of the Mississippi River, fuelled by excess nitrogen from upstream.

Pesticides also contribute to air pollution. They can contaminate both indoor and outdoor air and affect human, animal, and plant health. Some pesticide ingredients stay in the atmosphere for a short time, while others linger for longer periods. While air pollution caused by pesticides is less well-documented than water or food contamination, the French government has identified eight substances used in pesticides, including chlorothalonil and folpel, that had annual average concentrations above 0.1 nanograms per cubic metre of air.

Overall, agricultural activities, including the use of pesticides and fertilizers, are a major source of air pollution. Food cultivation is the dominant source of fine particulate matter (PM2.5) in ambient air in Europe, the central US, and parts of China. To improve air quality, the agricultural sector needs to reduce emissions significantly by 2030.

Livestock waste

Ammonia emissions from livestock waste occur primarily through the storage of manure and silage, which is more prevalent in feedlot animal operations compared to pasture-raised herds. The practice of housing livestock in confined feeding operations, known as Concentrated Animal Feeding Operations (CAFOs), makes their contribution to air pollution challenging to estimate. The emissions from these operations depend on factors such as animal type, population size, and farm management policies.

The air near large-scale industrialized pig, chicken, and dairy cow operations can be hazardous to public health. However, due to exemptions in reporting air emissions, the exact composition of the air surrounding these facilities is often unknown. A 2017 court decision aimed to address this issue by requiring farmers and ranchers to report hazardous emissions from animal waste, such as ammonia and hydrogen sulfide, when they exceeded certain thresholds.

To address the issue of livestock waste emissions, accurate emission tracking and effective reduction strategies are crucial. This includes developing process-based models to track and monitor livestock emissions and investigating the meteorological impact of these agricultural emissions. Additionally, practices such as sustainable application of livestock waste to fields can help mitigate emissions at farms with lower animal densities.

It is important to note that agricultural pollution, including livestock waste, interacts with industrial emissions. Ammonia from livestock waste can react with emissions of nitrogen oxides (NOx) and sulphur dioxide (SO2) from traffic and industry, leading to the formation of secondary particles that further contribute to air pollution.

Fossil fuel consumption

Moreover, the agricultural sector's direct energy use for crop management and indirect energy use for machinery and equipment also contribute to fossil fuel consumption. The use of diesel-powered farm equipment and engines releases NOx and PM emissions, further adding to air pollution. The interaction between agricultural activities and industrial emissions exacerbates the problem, as ammonia (NH3) from heavily fertilized fields and livestock waste combines with oxides of nitrogen (NOx) and sulphur (SO2) from traffic and industry, leading to the formation of secondary particles that can cause harm to human health and the environment.

In addition to fertilizer production and direct energy use, the application of pesticides and the use of fossil fuels in the drainage of organic soils on farms also contribute to fossil fuel consumption and air pollution. The complex relationship between energy inputs and yields in agriculture can lead to higher energy demands and increased dependence on fossil fuels. As agricultural producers strive to optimize energy inputs and meet the growing global demand for food, the interplay between energy consumption and yield gains becomes crucial.

To address the environmental and health impacts of fossil fuel consumption in agriculture, efforts are being made to reduce emissions and transition to more sustainable energy sources. Studies have proposed targets for the agricultural sector to lower emissions, and initiatives such as the National Clean Diesel Campaign offer funding for farmers adopting clean diesel technologies. Additionally, some industries are exploring alternatives to fossil fuels, such as hydrogen, to reduce their carbon footprint and mitigate the effects of global warming.

While agriculture's contribution to overall fossil fuel consumption may be relatively small compared to other sectors, it is still significant. The continued growth in energy consumption by the agricultural sector and its increasing dependence on fossil fuels highlight the urgent need for sustainable practices and renewable energy solutions. By reducing fossil fuel consumption and transitioning to cleaner energy sources, the agricultural sector can play a crucial role in mitigating air pollution and contributing to global efforts to combat climate change.

Soil management

Emissions of Dust, NH3, and Greenhouse Gases: Agricultural soils can release harmful emissions into the atmosphere if not properly managed. This includes dust, ammonia (NH3), and greenhouse gases such as nitrous oxide. Nitrogen-based fertilizers applied to the soil can escape and turn into nitrous oxide, a potent greenhouse gas that contributes to global warming.

Tillage Practices: Tillage, or soil cultivation, can increase wind erosion, leading to dust emissions and air pollution. Alternative practices, such as reduced tillage or no-till farming, can help mitigate this issue.

Crop Diversity and Rotation: Implementing crop diversity and rotation practices can improve soil health and reduce the need for excessive fertilizers, which contribute to air pollution when they wash off fields and release nitrogen into water bodies and the atmosphere.

Cover Cropping: Planting cover crops is a soil management technique that protects the soil from erosion, nutrient depletion, and weed growth. By improving soil health and structure, cover crops can help reduce dust emissions and improve the soil's ability to sequester carbon, benefiting air quality.

Manure Management: Proper storage, treatment, and use of nutrient-rich animal manure are essential. Improper management of manure can lead to the release of harmful gases, such as ammonia and greenhouse gases, into the atmosphere.

Integrated Pest Management (IPM): Adopting IPM practices can reduce the reliance on chemical pesticides and herbicides, preventing chemical drift and reducing overall emissions from agricultural operations.

By implementing sustainable soil management practices, farmers can play a crucial role in mitigating air pollution, improving local air quality, and contributing to the fight against climate change. These practices also help maintain soil health and fertility, ensuring long-term productivity and food security.

Manure management

To mitigate this, farmers can adopt specific manure management practices. These include maintaining an appropriate balance between agronomic requirements and environmental impacts. For example, excessive manure application can result in negative consequences such as soil pollution due to the addition of heavy metals, organo-chlorines, and excessive salts. Additionally, the uneven distribution of faeces and urine on grazing lands can lead to substantial leaching losses, with potential environmental implications.

Another important consideration in manure management is the formation of methane (CH4) and ammonia (NH3). Methane is produced during the decomposition of manure under anaerobic conditions. Disturbing stored manure can release CH4 into the atmosphere, contributing to ozone layer depletion over time. Similarly, ammonia (NH3) is formed through the volatilization process when manure is exposed to air. The larger the exposed surface area, the greater the amount of NH3 volatilization.

Agricultural burning, a common practice in manure management, also contributes to air pollution. The burning of manure releases particle plumes of smoke, dust, and/or coloured gases, leading to regional haze and reduced visibility. These emissions, along with industrial and natural sources, interact to impact air quality. The production of artificial fertilizers, which has skyrocketed to meet the demands of a growing population, further exacerbates the problem.

To address these issues, organizations like the US Environmental Protection Agency (EPA) have implemented initiatives such as the National Clean Diesel Campaign. This campaign aims to assist farmers in financing clean diesel initiatives and reducing diesel emissions from farm equipment. By collaborating with farmers and conducting studies on air emissions, the EPA strives to establish federal standards that limit emissions and provide guidance on emission reduction practices for crop and animal farms.

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