Agricultural Air Pollution: Farming's Impact On Air Quality

Despite the agricultural industry being crucial in producing enough food for the global population, it is also one of the most damaging sectors on the planet. Agriculture is a significant source of air pollution, with agricultural activities such as the application of fertilisers and insecticides, the rearing of livestock, the use of heavy-duty machinery, and the burning of crop stubble contributing to poor air quality. These practices can also contribute to climate change and global warming. For example, the production of artificial fertilisers has skyrocketed from about 20 million tons in 1950 to nearly 190 million tons today, with about a third of them being nitrogen-based. The chemicals contained within these products can be blown off course or evaporate into the air, thus contaminating the local atmosphere.

Livestock rearing

One of the primary sources of air pollution from livestock rearing is enteric fermentation, which leads to methane emissions. Methane is produced during the digestive process of ruminant animals, such as cows, and is released into the atmosphere. In addition to methane, livestock waste, particularly from feedlot animals, is a significant contributor to ammonia emissions. Ammonia emissions from livestock waste can affect air quality, leading to respiratory problems and premature deaths. The rise in ammonia mixing ratios, as indicated by satellite records, is a concerning trend.

The environmental impact of livestock rearing is further exacerbated by the large amounts of water required for meat production. Processing one pound of beef, for example, uses 2,500 gallons of water. This contributes to water pollution, as livestock waste contains antibiotics, hormones, and other chemicals that can contaminate water sources. Additionally, the livestock business contributes to land degradation, with overgrazing, compaction, and erosion affecting about 20% of pastures.

To address the air pollution caused by livestock rearing, there have been efforts to develop accurate process-based models to track and reduce livestock emissions. Improving animal diets, implementing soil conservation methods, and adopting controlled livestock exclusion from sensitive areas are some of the proposed solutions. Smarter production methods, such as improving the nutrition and genetics of livestock, can also help reduce their environmental impact.

It is worth noting that the impact of livestock rearing on air pollution varies depending on the animal type, population size, and farm management policies. While there have been challenges in quantifying the exact number and size of CAFO sites, it is clear that livestock rearing has a significant contribution to air pollution and global warming.

Stubble burning

The burning of crop stubble releases various gaseous pollutants and particulate matter into the atmosphere. These include carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), methane (CH4), and PM10 and PM2.5 particles. These pollutants have detrimental effects on both human health and the environment. The fumes from stubble burning can cause skin and eye irritation, as well as more severe respiratory diseases, asthma, cardiovascular issues, and even cancer. The pollution resulting from stubble burning also increases mortality rates due to prolonged exposure.

In North-western India, stubble burning has been identified as a major contributor to the poor air quality in Delhi, the National Capital Region (NCR), and other surrounding areas. The smoke from burning fields can travel long distances, adding to the toxic haze that affects the health of millions of people. During certain periods, such as late morning to afternoon, and in specific months like October and November, the contribution of stubble-burning fires to air pollution in these regions can be as high as 30-35%.

The practice of stubble burning also has negative consequences for soil fertility and the environment. It leads to nutrient loss, depletion of soil organic matter, and a reduction in beneficial soil biota. Additionally, it undermines the soil's capacity for water retention, affecting agricultural productivity in the long term. Despite the short-term economic benefits for farmers, the environmental and health costs of stubble burning are significant.

To address the issue of stubble burning and its impact on air pollution, alternative management practices have been proposed. These include incorporating stubble into the soil, using it as fuel in power plants, or as raw material for the pulp and paper industry, or for biofuel production. In Punjab, India, the government has also subsidised equipment like Rice Straw Shredders and Happy Seeders, which help manage rice stubble more effectively without burning. By adopting these environmentally friendly alternatives, farmers can not only protect their crops and the environment but also improve air quality and public health.

Use of heavy machinery

The use of heavy machinery in agriculture has been linked to air pollution in several ways. Firstly, the combustion of fossil fuels, such as diesel, used to power internal combustion engines of farm vehicles like tractors and combine harvesters, generates significant carbon emissions. This contributes to the overall carbon footprint of the agricultural sector and exacerbates climate change.

Secondly, heavy agricultural machinery can cause soil compaction, a phenomenon characterized by increased soil density, reduced air volume, and impaired drainage capacity. This compaction can lead to poorer crop yields and increased pollution from agricultural land. The negative effects of soil compaction can persist for generations, especially in deeper layers of soil. Additionally, compacted soil loses nitrogen more easily, as nitrate is converted into nitrous oxide, which is a potent greenhouse gas.

Moreover, the weight of heavy agricultural machinery can exceed 60 tonnes, exerting excessive pressure on the soil and leading to permanent compaction damage. This weight contributes to soil erosion, which not only affects soil quality but also carries nutrient sediments that pollute waterways. Soil erosion further exacerbates air pollution by releasing dust and particulate matter into the atmosphere.

To address these issues, it is essential to implement measures that reduce the carbon emissions associated with heavy machinery. This can include transitioning to alternative energy sources, improving engine efficiency, and adopting sustainable farming practices that minimize the need for heavy machinery. By mitigating the environmental impact of heavy machinery in agriculture, we can contribute to improving air quality and combating climate change.

Application of fertilisers and insecticides

The application of fertilisers and insecticides is a double-edged sword in agriculture. While they enhance crop yields, their excessive use has detrimental effects on the environment and human health, contributing to air pollution.

Application of Fertilisers

Fertilisers are essential in modern agriculture, providing crops with the necessary nutrients, such as nitrogen and phosphorus, for growth. However, the overuse of synthetic fertilisers has led to a significant environmental impact. During their manufacturing, harmful gases such as sulphur oxide (SOx), ammonia (NH3), nitric oxide (NO), and nitrogen dioxide (NO2) are released, contributing to air pollution. These gases directly affect both the environment and human health. For instance, nitrogen oxides, a byproduct of inorganic fertilisers, remain in the atmosphere and, when inhaled, can cause respiratory diseases, circulatory system disorders, and damage to organs. The excessive use of fertilisers also leads to nutrient runoff, where excess nitrogen and phosphorus wash off fields, polluting waterways and contributing to eutrophication and aquatic life loss.

Application of Insecticides

Insecticides are indispensable in agricultural production, controlling pests and weeds to increase crop yields. However, their use contributes to air pollution and poses risks to human health. During spraying in agricultural areas, about 30-50% of pesticides are dispersed into the air through drift (wind) and evaporation. These pesticides then contaminate the air, soil, water, and crops, impacting other organisms and the food chain. Climate change-induced alterations in weather patterns and pest behaviours also influence pesticide requirements, potentially intensifying their use and increasing the risk of air pollution.

The adverse effects of insecticides on human health have been well-documented. For example, studies have shown a link between the presence of ethylene thiourea in urine, a byproduct of certain fungicides, and the occurrence of asthma and rhinitis in children. Additionally, pesticide spray seasons amplify the likelihood of exposure, particularly in young children, leading to temporary increases in blood pressure.

To mitigate the risks associated with the application of fertilisers and insecticides, it is crucial to adopt sustainable practices, improve application technologies, and implement robust policies and regulations. By addressing these issues, we can ensure the safe and sustainable use of these substances for human health and the environment.

Ammonia emissions

Ammonia (NH3) contributes to the formation of fine particulate matter (PM2.5), which can cause respiratory issues and lead to premature mortality. In the US, Europe, and China, ammonia emissions from agriculture are a major concern, as they contribute significantly to air pollution and its associated health impacts.

The health impacts of atmospheric ammonia released from agricultural activities include reduced lung function, irritation to the throat and eyes, and increased coughing and phlegm expulsion. These effects are particularly relevant for those who handle livestock, as they are directly exposed to the emissions.

Additionally, ammonia can react with other contaminants in the air, forming dangerous aerosols and contributing to acidification. This further exacerbates the negative impact of agricultural activities on air quality and the environment.

Reducing ammonia emissions from agricultural practices is crucial to mitigating these adverse effects on human health and the environment. Lowering NH3 emissions can be easier to achieve than reducing other associated pollutants, making it a cost-efficient way to protect human health and improve air quality.

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