Air Quality Issues in Sustainability: Greenhouse Gases and Volatile Organic Compounds - Sustainable Animal Agriculture - page 133

improving our understanding is necessary to
advance the sustainability of animal agricul-
ture production systems.

output (e.g. per kg of milk or pork) is more
appropriate than reporting per animal unit
due the variability across farms. Improving
production efficiency is a powerful and proven
method to reduce GHG emissions per unit of
output from animal production systems. VOCs
are precursors to tropospheric O 3 ; however,
not all VOCs contribute equally to O 3 forma-
tion, which needs to be considered when eval-
uating the sustainability of animal agriculture
production systems. The major source of VOC
emissions on farms is fermented feeds and to a
lesser extent fresh manure. Mitigation of VOCs
from fermented feeds should also reduce the
loss of feed dry matter, and improve the eco-
nomic profitability of the feeding enterprise
on farms. In summary, reducing animal agri-
culture's impact on air quality will contribute
to the industry's long-term environmental
sustainability.

Conclusion

Air quality is a critical component of sustain-
able animal agriculture systems. GHG and
VOC emissions from animal production sys-
tems can arise from the animals directly, their
manure and from their feeds. Methane emis-
sions from enteric fermentation and manure
stored under anaerobic conditions result from
microbial processes. Nitrous oxide emissions
mostly come from nitrification and denitrifi-
cation bacterial processes; therefore, direct
mitigation of GHG emissions requires manipu-
lation of microbial populations or their envi-
ronment. Reporting GHG emissions per unit of

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