{"id":22441,"date":"2024-01-23T09:00:36","date_gmt":"2024-01-23T14:00:36","guid":{"rendered":"https:\/\/www.vrg.org\/blog\/?p=22441"},"modified":"2024-01-08T13:54:23","modified_gmt":"2024-01-08T18:54:23","slug":"cafo-ammonia-a-major-source-of-pm2-5-air-pollution","status":"publish","type":"post","link":"https:\/\/www.vrg.org\/blog\/2024\/01\/23\/cafo-ammonia-a-major-source-of-pm2-5-air-pollution\/","title":{"rendered":"CAFO Ammonia: A Major Source of PM2.5 Air Pollution"},"content":{"rendered":"

Nitrogen in manure from confined animal feeding operations (CAFOs<\/a>) is one of the major sources of water<\/em> pollution. The major form that nitrogen takes when it is in water is as the ammonium ion (NH4<\/sub>+<\/sup>).<\/p>\n

In drain or window cleaner, liquid ammonia exists as an ammonium ion<\/a>, too. However, when in contact with the air, ammonia gas<\/em> (NH3<\/sub>) forms. You know it by its choking fumes. Ammonia in gaseous form is a source of air<\/em> pollution.<\/p>\n

You may not know that ammonia generated from manure is also a leading source of particulate matter<\/em> air pollution, commonly called PM2.5<\/sub> air pollution. Solid particles 2.5 microns or smaller in diameter, PM2.5<\/sub> pollution is a silent killer responsible for over four million deaths<\/a> annually.<\/p>\n

In this article, we examine the fate of CAFO ammonia. We focus on how ammonia contributes to PM2.5 <\/sub>pollution in the air we breathe.<\/p>\n

Where does ammonia come from?<\/strong><\/p>\n

Ammonia is formed in nature by microorganisms during their physical and chemical breakdown of organic matter (dead plants and animals). The amount of ammonia naturally present, usually in rainwater, from these processes is 1-5 parts per billion<\/a> (ppb).<\/p>\n

Ammonia is also a major industrial chemical synthesized from fossil gas<\/a>. It is used to make numerous products including chemical fertilizers. As a fertilizer, ammonia or similar substances such as urea<\/a>, are sprayed on farm fields or injected into soil.<\/p>\n

Because of the great inefficiency \u2013 up to 80% \u2013 in the grain:meat conversion process as we detailed in a previous article<\/a>, animals excrete waste products high in nitrogen. As microbes decompose the feces and urine, ammonia is released. In CAFOs, ammonia emanates from animal housing, manure lagoons, or the manure sprayed on fields, becoming an air contaminant.<\/p>\n

In this article, we use the word manure<\/em><\/a> as the United States Environmental Protection Agency (USEPA) does: \u201c…the combination of manure (i.e., the mixture of feces and urine), water directly or indirectly used in animal production activities…, and other wastes (e.g., hair, bedding, soil, feed) that are mixed with manure.\u201d<\/p>\n

Here is an infographic taken from the UK government website<\/a> showing how ammonia cycles through the environment:<\/p>\n

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infographic taken from the UK government website<\/p><\/div>\n

How much ammonia comes from agriculture in the United States?<\/span><\/b><\/p>\n

According to the <\/span>2020 National Emissions Inventory (NEI) Report<\/span><\/a> (under the 2020 NEI Updates tab at that link, slide #10), the total amount of ammonia generated from agricultural fertilizer<\/i> increased 60% in 2020 over 2017 levels (1.8 million tons vs. 1.1 million tons).<\/span><\/p>\n

This fertilizer is applied to all conventionally grown crops, the large majority of which is animal feed. <\/span><\/p>\n

How much ammonia comes from livestock in the United States?<\/span><\/b><\/p>\n

The Ohio State University Extension Service compiled USEPA statistics on ammonia release by various animals from 2004 in a <\/span>pie chart<\/span><\/a> depiction:<\/span><\/p>\n

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Here is a general overview of <\/span>2004 data<\/span><\/a> arranged by USEPA showing a 71%<\/b> contribution by livestock to national ammonia emissions. Note that an additional 14% is due to agricultural fertilizers, a comparatively smaller portion of which is used for crops consumed by humans. So, roughly 85%<\/b> of all ammonia emissions in the U.S. in 2004 was derived from agriculture.<\/span><\/p>\n

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We located a 2004 USEPA document<\/a> that projected livestock ammonia emissions through 2030. Here is a screenshot of that table:<\/p>\n

\"\"<\/a>We notice from this projections table that USEPA predicts ammonia emissions between 2020 to 2030 will increase for beef and poultry, stay roughly the same for dairy, and decrease for pigs.<\/p>\n

How much does livestock contribute to ammonia emissions in other countries?<\/em><\/strong><\/p>\n

In 2016<\/a><\/em>, animal agriculture was responsible for 88%<\/strong> of ammonia emissions in the United Kingdom. <\/em><\/p>\n

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You can see China information at: https:\/\/acp.copernicus.org\/preprints\/acp-2021-439\/acp-2021-439.pdf<\/a><\/p>\n

In China, ammonia emissions came from the sources depicted on the pie chart for 2016. Their breakdown is much more detailed. Ammonia emissions from all fertilizer-related, agricultural, and livestock sources is roughly 91%<\/strong>.<\/p>\n

How does ammonia form PM2.5<\/sub> particle pollution?<\/strong><\/p>\n

Fine particle pollution PM2.5\u00a0forms by chemical reactions between gaseous ammonia and sulfuric or nitric acids. These two acids are derived from sulfur oxides<\/a> and nitrogen oxides<\/a> (common air contaminants noted as SOx<\/sub> and NOx<\/sub>, mostly from gas- or diesel-powered vehicle exhaust or power plants). The reactions result in ammonium sulfate, ammonium bisulfate, and ammonium nitrate. These compounds exist in the solid state as extremely small yellow or white crystalline particle pollution in air.<\/p>\n

A 2011 study<\/a> published in the Journal of Dairy Science<\/em> found that ammonia from CAFOs is responsible for, on average, 5-11%<\/strong> of all<\/em> PM2.5 pollution. The percentage varies widely with higher amounts in the vicinity of CAFOs or downwind from them. It\u2019s also higher in cooler weather. In some areas at certain times of the year, it could be up to 20%<\/strong> of total PM2.5.<\/p>\n

Does ammonia cause nitrous oxide to form?<\/strong><\/p>\n

Ammonia is used to manufacture nitric acid<\/a>, a primary ingredient in fertilizers. That chemical transformation releases nitrous oxide (N2<\/sub>O) emissions.<\/p>\n

Nitrous oxide \u2013 also used by dentists as laughing gas \u2013 is a potent greenhouse gas, contributing to the climate emergency. Most nitrous oxide emissions (74%<\/strong>) come from agricultural soil management<\/a> which includes:<\/p>\n