(NH3) is a chemical compound which has significant importance within
the natural world. It is a stable colourless gas which, in nature, is produced
by nitrogen fixing microorganisms that convert atmospheric nitrogen (N2)
into NH3. Nitrogen
is needed by all living organisms for growth and survival, therefore, organic
matter contains large amounts of it in the form of proteins, amino acids and
organisms excrete waste or die, the organic matter is decomposed by
microorganisms which convert that “organic nitrogen” into inorganic ammonia
through the process of ammonification. There
are therefore two biological routes through which ammonia can be released into
the environment: nitrogen fixation and ammonification.
digestion (AD) is a process through which organic matter (such as food waste,
manure or bakery waste for example) is placed in an oxygen-deprived environment
where microorganisms digest and decompose it. This leads to the release of biogas
– which can be used for bioenergy purposes – and to the production of
digestate, which is the portion of the organic matter which could not be fully
digested into gas[iv]. AD-derived
biogas is mainly made up of CO2 and methane, however it also
contains other trace gases such as NH3. Digestate
is also rich in mineralised N in the form of NH4+ and NH3.
is not a greenhouse gas (GHG). Once released in the atmosphere, the molecules
of ammonia only last a few hours before finding their way back to the surface,
either in the form of dry deposition (as a gas) or in the form of wet
deposition (as ammonium in precipitation). As
the ammonia deposits back onto the surface, in soils or water bodies, it can
create a surplus of nutrient in aquatic ecosystems. This phenomenon is referred
to as eutrophication. As the habitat’s nutrient content increases due to the
high N input, algal growth significantly increases on the surface of the water,
leading to light being blocked from reaching below the surface and preventing
oxygen from entering the system as well. This leads to hypoxia and eventually
to a complete deregulation of the ecosystem and biodiversity loss. Eutrophication
also leads to the breakdown of ecosystem services on which human populations
rely, such as water quality and pathogen regulation for example. Ammonia
molecules in the atmosphere can also bind to other compounds such as sulfuric
acid and nitrate to form particulate matter (PM), which are a form of
anthropogenic aerosols. These PMs may cause more direct harm to the environment
and to human health.
In 2016, PM pollution was linked to 374 000 premature deaths in the EU.
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