Ammonia is a gas (NH3)
and a common pollutant from landfills, sewage treatment plants, and livestock agriculture
operations. Other sources include crop
agriculture from the volatilization of nitrogen fertilizer, wildfires, car
exhaust, human waste, industry, and natural sources such as decomposition in
the ocean. In plant and animal agriculture the ammonium (NH4) in solution from fertilizer
or livestock waste is volatilized into ammonia and hydrogen. Once volatized into
gaseous form it becomes mobile and is released into the atmosphere. The table
below shows the sources of ammonia pollution globally. Agriculture is responsible
for over 70% of global ammonia emissions. About 47% of the total is from
livestock agriculture, and 23% of the total is from fertilizer volatilization. Two-thirds of agricultural ammonia emissions come
from livestock agriculture and one-third from crop agriculture.
Ammonia is one of those chemicals that can be beneficial or
detrimental. Like methane, it can be used to provide power as it releases its
hydrogen, either through combustion or fuel cells. That, of course, requires
concentrated pure ammonia that is produced chemically. The sources of ammonia
in crop agriculture are non-point sources. Landfills can capture it if they are
equipped to capture gas. Manure and urine collection ponds can be outfitted to
recover methane, ammonia, and other anaerobic decomposition gases.
A 2024 paper in Nature
Sustainability explores the economic and environmental benefits of ammonia
recovery alongside the recovery of hydrogen for fuel and hydrogen peroxide (H2O2). The
researchers developed an electrode to oxidize organic matter which also
chemically uptakes ammonium and potassium ions. The abstract of the paper
explains it. The graphs are from the paper.
Abstract
“Livestock manure wastewater, containing high levels of
ammonia, is a major source of water contamination, posing serious threats to
aquatic ecosystems. Because ammonia is an important nitrogen fertilizer,
efficiently recovering ammonia from manure wastewater would have multiple
sustainability gains from both the pollution control and the resource recovery
perspectives. Here we develop an electrochemical strategy to achieve this goal
by using an ion-selective potassium nickel hexacyanoferrate (KNiHCF) electrode
as a mediator. The KNiHCF electrode spontaneously oxidizes organic matter and
uptakes ammonium ions (NH4+) and potassium ions (K+) in manure wastewater with
a nutrient selectivity of ∼100%. Subsequently, nitrogen- and
potassium-rich fertilizers are produced alongside the electrosynthesis of H2
(green fuel) or H2O2 (disinfectant) while regenerating the KNiHCF electrode.
The preliminary techno-economic analysis indicates that the proposed strategy
has notable economic potential and environmental benefits. This work provides a
powerful strategy for efficient nutrient (NH4+ and K+) recovery and
decentralized fertilizer and chemical production from manure wastewater, paving
the way to sustainable agriculture.”
A 2019 study in
the U.K. by the Bureau of Investigative Journalism found that the country on;ly
monitors ammonia air pollution from the largest intensive poultry and pig farms,
but not from cow and dairy farms which produce far more ammonia. It’s also
true, however, that those intensive, more confined operations can produce more
ammonia pollution over a small local area.
Gaseous ammonia
contributes significantly to particulate matter pollution, particularly the
most dangerous smaller form, PM2.5. The investigation explains:
“Ammonia travels on the wind and can mix with industrial
and car fumes, creating a form of “particulate matter”, PM 2.5, that has been
linked to higher death rates, respiratory problems, cardiovascular diseases,
cognitive decline and low birth weights.”
“PM2.5 is probably responsible for somewhere between half
and three quarters of the total harm we derive as humans from air pollution,”
said Alastair Lewis, a professor of atmospheric chemistry at the National
Centre for Atmospheric Science. He said about half of PM2.5 in urban areas is
associated with ammonia.”
The graphs below
are from the investigation showing fate and transport, human health effects, UK
data, and UK ammonia hotspots.
A 2011 paper in Agriculture,
Ecosystems & Environment investigated ammonia pollution generation and
mitigation from pig houses.
“The main factors influencing NH3 production are the
floor type, the manure removal system, the climatic conditions inside the
building, the diet composition and the feed efficiency of animals.”
More bedding is associated
with less ammonia production. Lower crude protein diets, higher fiber diets,
and additives can lower ammonia emissions.
“The reduction of the slurry pit surface thanks to sloped
pit walls are related to proportional reductions of NH3 emissions. Frequent
manure removal, flushing and separating urine from faeces by V-shaped scraper
or conveyor belts reduce the NH3 releases from the buildings by about 50%.
However, the emissions during the storage period outside the building have to
be taken into account for a whole assessment of the technique.”
Ammonia emissions
are also affected by ambient temperature and ventilation conditions.
A 2025 paper in
Environmental Science and Technology led by researchers from the University of
Virginia explored environmental justice issues around ammonia pollution from
pig farms in Eastern North Carolina. The paper concludes that minority
communities are being disproportionately polluted by those operations.
“Concentrated animal feeding operations (CAFOs) emit
various harmful and noxious air pollutants, including ammonia (NH3). There are
limited measurements of CAFO-related air quality, contributing to disputes
around its severity. We use NH3 vertical column densities from the space-based
Infrared Atmospheric Sounding Interferometer (IASI) to report systematic,
distributive inequalities in NH3 column enhancements (ΔNH3 columns), equal to
NH3 columns less an observationally determined tropospheric background. Population-weighted
block group-scale ΔNH3 columns are higher by 27 ± 3% for Black and African
Americans, 35 ± 3% for Hispanics and Latinos, and 49 ± 3% for American Indians
compared to non-Hispanic/Latino whites in Eastern North Carolina (April–August
2016–2021).”
"The satellite ammonia measurements are independent,
observational evidence of inequalities in the air pollution impacts of
industrial swine operations across Eastern North Carolina," said Pusede.
"The satellite measurements are consistent with residents' claims of
unfair and unaddressed air quality issues and highlight the urgent need for
regulatory action."
References:
Deadly
gas: Cutting farm emissions in half could save 3,000 lives a year. The Bureau of Investigative Journalism. Andrew Wasley,
Alexandra Heal, and Mie Lainio. June 13, 2019. Deadly
gas: Cutting farm emissions in half could save 3,000… | TBIJ
Air
pollution inequities linked to industrial swine facilities are detectable from
space. Science X staff. Phys.org. January 28, 2025. Air
pollution inequities linked to industrial swine facilities are detectable from
space
Ammonia
emissions from pig houses: Influencing factors and mitigation techniques. François-Xavier
Philippe, Jean-François Cabaraux, and Baudouin Nicks. Agriculture, Ecosystems
& Environment. Volume 141, Issues 3–4, May 2011, Pages 245-260. Ammonia
emissions from pig houses: Influencing factors and mitigation techniques -
ScienceDirect
Ammonia
pollution. Wikipedia. Ammonia
pollution - Wikipedia
Electrochemical
ammonia recovery and co-production of chemicals from manure wastewater. Rui
Wang, Kai Yang, Cindy Wong, Horacio Aguirre-Villegas, Rebecca Larson, Fikile
Brushett, Mohan Qin & Song Jin. Nature Sustainability volume 7,
pages179–190 (2024). Electrochemical
ammonia recovery and co-production of chemicals from manure wastewater | Nature
Sustainability
Satellite
Observations of Atmospheric Ammonia Inequalities Associated with Industrialized
Swine Facilities in Eastern North Carolina. Akirah Epps, Isabella M. Dressel, Xuehui
Guo, Maghogho Odanibe, Kimberly P. Fields, Ann Marie G. Carlton, Kang Sun, and Sally
E. Pusede. Environmental Science & Technology. 2025. Satellite Observations
of Atmospheric Ammonia Inequalities Associated with Industrialized Swine
Facilities in Eastern North Carolina | Environmental Science & Technology
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