Agricultural Air Pollution: Farming's Impact On Air Quality

Agriculture is a significant contributor to air pollution worldwide. While air pollution from agriculture includes emissions from tractors and other farm vehicles, the greatest agricultural contributors to air pollution are animal-raising operations and the heavy use of fertilizers. Animal-raising operations release methane, nitrous oxide, and ammonia into the air, while fertilizers play a crucial role in boosting crop yields, with fumes from nitrogen-rich fertilizers combining with industrial emissions to form solid particles. These particles can penetrate deep into the lungs, causing heart or pulmonary disease, and have been estimated to cause at least 3.3 million deaths each year globally. In addition, the burning of crop stubble, a commonplace practice throughout Asia, produces much air pollution and negatively impacts those far from the source of the pollution due to strong winds.

Livestock rearing releases methane, nitrous oxide, ammonia, and hydrogen sulphide

Livestock rearing is a significant contributor to air pollution, releasing methane, nitrous oxide, ammonia, and hydrogen sulphide into the atmosphere. These gases are harmful to both the environment and human health.

Methane, a greenhouse gas, is produced in large quantities by the digestive systems of ruminants, such as cattle, sheep, and goats. It has a Global Warming Potential (GWP) 23 times that of carbon dioxide (CO2). Methane emissions from livestock can be mitigated through improved animal diets and manure management techniques such as anaerobic digestion and subsurface injection.

Nitrous oxide, another potent greenhouse gas, is generated during the decomposition of manure and through microbial processes in the soil. It has a GWP 296 times that of CO2. Nitrous oxide emissions can be reduced by managing the fate of ammoniacal nitrogen and implementing practices such as solids separation, urease and nitrification inhibitors, and matching plant nutrient requirements with manure fertilization.

Ammonia is a volatile gas that escapes from manure and livestock waste, reducing the amount of nitrogen available for plant growth. It contributes to air pollution, the formation of particulate matter, and acid rain. Ammonia emissions can be lowered by improving manure management practices and reducing nitrogen loss during cleaning and storage.

Additionally, livestock operations produce hydrogen sulphide, which contributes to air pollution and has negative impacts on human health. While specific mitigation strategies for hydrogen sulphide were not found, general recommendations for reducing air pollution from livestock include soil conservation methods, controlled livestock exclusion from sensitive areas, and the implementation of biogas plant initiatives to recycle manure.

Overall, addressing air pollution from livestock rearing is crucial for both environmental sustainability and human well-being, and a range of strategies exist to mitigate these emissions.

Burning of crop stubble, a common practice in Asia, produces air pollution

Agriculture is a significant contributor to air pollution worldwide. Food production is responsible for a quarter of the world's greenhouse gas emissions. While air pollution from agriculture includes emissions from tractors and farm vehicles, the greatest agricultural contributors to air pollution are animal-raising operations and the heavy use of fertilizers.

In Asia, a significant source of air pollution is the burning of crop stubble, which is a common practice in the region. This method is used to remove paddy crop residues from the field to sow wheat, usually from the last week of September to November. The burning of crop stubble releases various gaseous pollutants, including carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), methane (CH4), and particulate matter (PM10 and PM2.5). These pollutants have severe impacts on both human health and the environment.

The Indo-Gangetic Plain, for example, is a hotspot for atmospheric pollutants, with seasonal crop residue burning being a major contributor. The burning of crop residue degrades the soil, increases the risk of erosion, and raises soil temperature, leading to the destruction of soil nutrients and microorganisms. This, in turn, affects soil fertility and economic development.

The practice of stubble burning also has economic implications. The high cost of incorporating, collecting, transporting, and processing crop residues in South Asia encourages farmers to burn crop residues. Labour shortages, the marketability of the crop residue, and the short time interval between harvests are additional factors that influence the decision to burn crop residues.

The impact of stubble burning on air quality is significant. In November 2019, Delhi recorded a peak Air Quality Index (AQI) of 487, while nearby areas reported similarly high levels. The health effects of air pollution from stubble burning can range from skin and eye irritation to severe neurological, cardiovascular, and respiratory issues, including asthma, chronic obstructive pulmonary disease (COPD), bronchitis, lung capacity loss, and emphysema. Prolonged exposure to high levels of pollution from stubble burning has also been linked to increased mortality rates.

Fertilisers, pesticides, and herbicides release chemicals that contaminate the atmosphere

The use of fertilisers, pesticides, and herbicides in farming is a significant contributor to air pollution. These chemicals are designed to improve crop production and protect crops from pests and weeds, but their use comes at a cost to the environment and human health.

Fertilisers, in particular synthetic fertilisers, are a major source of air pollution. During the manufacturing process, soot and dust particles are emitted, along with polluting gases such as sulphur oxide (SOx), ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2), and volatile organic compounds (VOCs). These emissions directly impact the environment and human health. Excess nitrogen returns to the atmosphere as nitrogen oxides, which have a much more harmful effect on the greenhouse effect than carbon dioxide. The fertiliser industry is essential for modern agriculture and sustaining the world's food supply, but its environmental impact cannot be ignored.

To mitigate the impact of fertilisers on air pollution, farmers can adopt sustainable practices such as using organic or mineral fertilisers, implementing crop rotation, and following guidelines for the suitable proportions and application of fertilisers. Organic fertilisers, derived from animal or vegetable carbonaceous materials, do not emit synthetic derivatives that pollute the air, water, and soil. They are absorbed more gradually by plants, allowing soil microorganisms to break them down first.

Pesticides and herbicides are also significant contributors to air pollution. These chemicals are designed to kill pests and weeds, but they can also have toxic effects on non-target organisms, including humans. Pesticides have been detected in the air in both rural and urban areas, with concentrations increasing in proximity to arable land. The potential toxicity of these chemicals to mammals, birds, earthworms, fish, honeybees, and humans is considerable, with potential health risks including acute toxicity, reproductive toxicity, carcinogenicity, and endocrine disruption.

The use of pesticides and herbicides can result in chemical drift, where these compounds spread beyond their intended application areas and contribute to poor air quality in nearby lands and neighbourhoods. This highlights the importance of responsible pesticide use, including following manufacturer directions, proper storage and disposal, increasing ventilation during indoor use, and exploring non-chemical methods of pest control where possible.

Diesel-powered farm vehicles and machinery generate carbon emissions

Diesel-powered farm vehicles and machinery are a significant contributor to air pollution. Diesel has been the primary fuel for farming for generations, and older diesel-powered tractors emit pollutants such as particulate matter, carbon monoxide, nitrogen oxides, and carbon dioxide. These emissions visibly dirty the air and have been targeted by environmental groups. The Clean Air Act has set emission standards to address this issue, and newer tractors are required to meet these standards. However, tractors built before the standards were implemented are exempt, and older diesel-powered tractors continue to contribute to air pollution.

The agricultural industry is transitioning towards net-zero emissions, and several alternatives to diesel fuel are being explored. One option is biomethane, which can be used in farm vehicles and machinery. Biomethane is a mature technology that has been used in road-going vehicles in the UK for several years. It can be distributed to farms through biomethane trucks or produced on-site at farm production sites. By using biomethane, farms can reduce methane emissions and initiate rapid transport decarbonisation.

Another alternative to diesel is electricity, which can power tractors and other farm machinery with lower emissions. Battery Electric Vehicles (BEVs) run on electric power stored in onboard batteries and produce zero tailpipe emissions, including greenhouse gases and air quality pollutant emissions such as particulates and NOx. BEVs can be charged from mains electricity or on-farm renewable energy sources such as solar panels, wind turbines, or biogas combustion. While BEVs are a viable option for smaller farm vehicles, they face challenges in terms of battery capacity and recharging times for heavier vehicles.

In addition to biomethane and electricity, other biofuels and alternative fuels are being considered for reducing carbon emissions in farm vehicles. These include ethanol, soy-based biodiesel, and hydrogen. While these options show promise in reducing environmental impact, they require further development and incentives to become economically feasible on a larger scale.

To offset the emissions from diesel-powered farm vehicles, farmers can purchase carbon credits. Each carbon credit represents the storage or sequestration of one metric tonne of carbon dioxide in the soil. By purchasing carbon credits, farmers can balance out the carbon emissions produced by their diesel-powered vehicles and contribute to carbon emission reduction efforts.

Air pollution from farms can impact areas beyond the immediate vicinity

Agriculture is a significant contributor to air pollution worldwide. Food production is responsible for a quarter of the world's greenhouse gas emissions, with ammonia emissions being the most impactful. The agricultural industry is crucial in producing enough food for the global population, but it is also one of the most damaging sectors.

Air pollution from farms can impact areas beyond their immediate vicinity. For example, chemical drift with pesticides, herbicides, and fertilizers can occur as these compounds reach nearby lands or neighbourhoods, contributing to poor air quality elsewhere. The heavy use of fertilizers is a major contributor to fine-particulate air pollution, and emissions from farms outweigh all other human sources of this type of pollution in much of the US, Europe, Russia, and China.

Fertilizers, which play a crucial role in boosting crop yields, can contaminate the local atmosphere when their chemicals are blown off course or evaporate into the air. The production of artificial fertilizers has skyrocketed from about 20 million tons in 1950 to nearly 190 million tons today, with about a third of them being nitrogen-based. As a result, nitrogen-rich fertilizers and animal waste can combine with industrial emissions to form solid particles, a significant source of disease and death. These fine particles can penetrate deep into the lungs, causing heart or pulmonary disease, and are estimated to cause at least 3.3 million deaths annually worldwide.

Additionally, the practice of stubble burning, common in Asia, produces significant air pollution. While prohibited in most countries, strong winds can carry the smoke over long distances, negatively impacting those far from the pollution source.

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