Livestock Waste: Air Pollution's Overlooked Culprit

The livestock industry has a significant impact on the environment. Raising livestock for human consumption generates nearly 15% of total global greenhouse gas emissions, with the global industry responsible for at least 51% of the greenhouse gases emitted into the atmosphere. In addition to contributing to climate change, livestock waste also pollutes the air with harmful chemicals and fumes. The US Environmental Protection Agency (EPA) has the authority to regulate Concentrated Animal Feeding Operations (CAFOs) under the Clean Water Act and Clean Air Act, but has faced pressure from the meat industry and yielded regulatory responsibility to the states. As a result, no one knows exactly what is in the air surrounding large-scale industrialized pig, chicken, and dairy cow operations, despite the hazardous effects on public health.

Ammonia emissions from livestock waste

Ammonia is a chemical compound composed of nitrogen and hydrogen, and it is a leading cause of air pollution. Livestock waste, particularly manure, is a significant contributor to ammonia emissions. Animal waste accounts for 50 to 85% of ammonia emissions in the United States, according to the Environmental Protection Agency (EPA) estimates. The global livestock system is one of the largest sources of ammonia emissions, and there is an urgent need for effective ammonia mitigation strategies.

Livestock operations, such as large-scale industrialized pig, chicken, and dairy cow farms, release harmful pollutants into the air, including ammonia. These emissions not only cause a persistent foul odour but also pose serious risks to human health and the environment. The air near these facilities can contain hazardous levels of ammonia, along with other pollutants like hydrogen sulfide and methane.

To address the issue of ammonia emissions from livestock waste, researchers have developed innovative strategies. One notable approach involves the acidification of manure and the inhibition of ureolytic bacteria. This method has shown promising results, achieving a 95.5% reduction in ammonia emissions from pig manure. Additionally, certain policies and incentives have been proposed to encourage the adoption of emission-reducing technologies in livestock operations. These include greenhouse gas offset credits, particulate matter offset credits, and expanded net metering policies to monetise electricity generated from captured methane gas.

While progress is being made, the regulation of air emissions from livestock waste remains a challenge. The livestock industry has historically been exempt from reporting hazardous air emissions, and the responsibility for regulation has largely been left to individual states. However, there are ongoing efforts to implement stronger laws and improve the existing regulatory framework to mitigate ammonia emissions from livestock waste effectively.

Hydrogen sulfide emissions from manure lagoons

Livestock waste is stored in open ponds, called lagoons, and is applied untreated as fertilizer to farm fields. These lagoons emit hydrogen sulfide (H2S), a major source of odor and an asphyxiant. H2S is formed from animal manure sulfur compounds, including primarily inorganic sulfate and organic sulfur compounds. Sulfate-reducing bacteria near the bottom of the lagoon produce HS- from the settled manure. The soluble HS- equilibrates with H2S as a function of pH.

The US Environmental Protection Agency (EPA) has the authority to regulate pollution from concentrated animal feeding operations (CAFOs) under the Clean Water Act (CWA) and Clean Air Act (CAA). However, the EPA has faced pressure from the livestock industry and yielded regulatory responsibility to the states. In 2017, a judge vacated an EPA rule exempting CAFOs from emissions reporting requirements, but the agency still does not set maximum pollutant levels.

Studies have measured hydrogen sulfide emissions from waste lagoons at hog and swine farms in different climate zones. Emissions were generally found to increase with wind speed. For example, measurements at a hog farm in North Carolina, USA, a humid mesothermal climate, found hydrogen sulfide emissions of 1.32 µg H2S m−2 s−1 ± 0.07 µg H2S m−2 s−1. In contrast, a hog farm in Oklahoma, USA, a semi-arid climate, had substantially higher emissions of 6.88 µg H2S m−2 s−1 ± 0.13 µg H2S m−2 s−1.

The high levels of hydrogen sulfide emissions from manure lagoons contribute to air pollution and pose health risks to nearby communities.

Particulate matter from dried manure

Unlike human waste, livestock manure is not treated before disposal. This untreated manure emits airborne chemicals and fumes, which can be hazardous to public health. In especially dry regions, manure easily turns into dust, and the particulate matter is rapidly dispersed.

The US Environmental Protection Agency (EPA) has estimated that nearly three-quarters of the country's ammonia pollution comes from livestock facilities. Studies have found high levels of antibiotics and antibiotic-resistant genes in air samples downwind of feedlots.

The EPA has the authority to regulate pollution from concentrated animal feeding operations (CAFOs) under the Clean Water Act (CWA) and Clean Air Act (CAA). However, due to pressure from the livestock industry, the EPA has shifted much of its regulating responsibility to the state level.

In 2017, a judge vacated an EPA rule that exempted CAFOs from emissions reporting requirements, meaning that many more livestock operations would be required to report their emissions. However, the EPA still does not set maximum pollutant levels for CAFOs, and federal law exempts farms from reporting air pollutants to federal agencies.

To address the issue of particulate matter from dried manure, treatments that increase the dry matter (DM) content of poultry manure should be avoided. Studies have shown a positive correlation between manure DM content and particulate matter release. Additionally, high manure DM leads to reduced microbial abundance and a lower risk of environmental pathogen dispersion. The optimal DM range for poultry manure field application is 50–70%.

Greenhouse gas emissions from confined livestock

The animal agriculture industry is a leading cause of environmental degradation, with waste in the meat industry being a major problem. Raising livestock for human consumption generates nearly 15% of total global greenhouse gas emissions, a figure that is greater than all transportation emissions combined.

Livestock production accounted for 14.5% of global greenhouse gas emissions, according to a 2013 estimate by the Food and Agriculture Organization of the United Nations. This figure is based on data from 2004-2005 and remains the most widely cited estimate of the industry's global carbon footprint. However, more recent data indicates that the true figure may be higher or lower. The Food and Agriculture Organization of the United Nations has since released a new, lower estimate of 12%, while peer-reviewed studies have placed the figure at up to 19.6%.

Sources of greenhouse gas emissions from livestock production include enteric fermentation, manure, and feed production. Enteric fermentation, the regular digestive process of ruminants such as cattle and sheep, produces methane. Over 90% of enteric methane from cattle is emitted through burping. Manure, or solid waste, produces both methane and nitrous oxide. Methane emissions are typically highest when manure is stored in liquid systems such as manure lagoons. Feed production involves manufacturing fertilizers and other farm inputs, which emit carbon dioxide, and fertilizing crops, which generate nitrous oxide emissions.

In the United States, the amount of waste produced by livestock in concentrated animal feeding operations (CAFOs), or factory farms, is significant. Unlike human waste, livestock manure is not treated before disposal. The untreated manure emits airborne chemicals and fumes, and when it enters waterways through runoff, it becomes a source of water pollution. The US Environmental Protection Agency (EPA) has the authority to regulate CAFO waste under the Clean Water Act and Clean Air Act, but has faced pressure from the meat industry and largely shifted responsibility to the state level.

Air pollution from industrial farming operations

The industrial farming of livestock for human consumption is a major contributor to air pollution. The process of raising livestock generates nearly 15% of total global greenhouse gas emissions, which is more than all transportation emissions combined. The air near large-scale industrialised pig, chicken, and dairy cow operations is not only unpleasant but can also be hazardous to human health.

Livestock manure, unlike human waste, is not treated before disposal. The untreated manure emits airborne chemicals and fumes, and when runoff occurs, dangerous pollutants enter waterways. In 2012, livestock and poultry on the largest concentrated animal feeding operations (CAFOs) produced 369 million tons of manure, almost 13 times more waste than that of the entire US population of 312 million.

The US Environmental Protection Agency (EPA) has the authority to regulate CAFO waste, but has yielded to pressure from the meat industry and shifted responsibility to individual states. While federal law gives the EPA the power to regulate CAFO waste, the reality is that most regulation occurs at the state level. The EPA has also released rules exempting CAFOs from emissions reporting requirements.

Ammonia, a colourless gas produced in animal metabolism and excreted through waste, is a significant pollutant. The EPA estimates that nearly three-quarters of the country's ammonia pollution comes from livestock facilities. Other pollutants include hydrogen sulfide, methane, nitrous oxide, volatile organic compounds, and particulate matter. These emissions can lead to respiratory problems and premature deaths, as well as negatively impacting the health of farm animals and workers.

The livestock industry's contribution to air pollution is difficult to quantify due to the varying sizes and locations of intensive agricultural operations. However, studies have found high levels of antibiotics and antibiotic-resistant genes in air samples downwind of feedlots. The top three meat companies in the world have a carbon footprint comparable to that of France or a major multinational oil and gas corporation.

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