Agriculture Reference
In-Depth Information
the silo (the area that is exposed to air) by not
opening more of the silo than is required and
keeping the face smooth to reduce the surface
area. Achieving this BMP goal will require proper
planning of the silo design and the proper equip-
ment to achieve a smooth face. Additionally,
precision feeding (i.e. managing a livestock nutri-
tional programme to precisely match an animal's
nutrient requirements based on their stage-of-life)
that requires tracking animal DMI and the dry
matter content of the feed can minimize extra
silage being fed to animals when it is not needed.
This could potentially reduce VOC emissions by
minimizing the exposed surface area of loose
silage in feed alleys on farms. Other innovative
ways to prevent or minimize VOC emissions from
fermented feeds will undoubtedly be put forth in
the coming years, and all will require experimen-
tal testing. Current and future solutions have
the benefit of not only preventing emissions of a
smog-precursor, but also minimizing costly losses
of feed dry matter and nutrients for farmers.
Water-soluble VOC emissions (e.g. the alco-
hols, ethanol and methanol) could be mitigated
from animal housing floors by flushing the
manure with water as was demonstrated by
Chung
et al
. (2010). However, consideration has
to be given to the VOC emissions from the end
point of this manure slurry (typical a lagoon)
and the water-use required for flushing animal
housing systems, which may be undesirable in
arid locations like California. Biofiltration sys-
tems are another possible VOC mitigation tech-
nique for ruminant and swine production
systems. A biofilter consists of a filter material
(e.g. wood chips, soil) that contains microorgan-
isms and can 'treat' the exhaust air from hous-
ing or manure storage system (Martens
et al
.,
2001; Pagans
et al
., 2007). Research has
shown biofilters can effectively reduce VOCs
from swine housing facilities (Martens
et al
.,
2001); however, wide-scale adoption of biofilters
would require demonstration of the environ-
mental benefits and economic costs to farmers.
emission mitigation strategies, is the acquisition
of accurate and precise emissions data. Thus,
capturing emissions from live animals, animal
housing systems and feed management systems
becomes essential. Having accurate and precise
data is also required for validation of models that
simulate or predict gaseous emissions from ani-
mal agriculture production. Measurement of
GHG and VOC emissions from animals, their
waste and feedstuffs can be measured in cham-
ber systems or under field conditions. An over-
view and description of the enteric CH
4
emission
measurement techniques for cattle can be found
in Johnson and Johnson (1995). These methods
include whole animal chambers, ventilated
hood systems, the sulfur hexafluoride technique
(a tracer gas method) and micrometeorologi-
cal techniques (Johnson and Johnson, 1995).
There are benefits and trade-offs with all of
these techniques, with chamber methods gen-
erally collecting more precise data per animal
than tracer or micrometeorological methods;
however, chambers are often more restricting of
the animal's natural behaviours (and normal
emissions) than the other less restrictive meth-
ods. For further information on measurement
techniques of GHG and ammonia, please see
Chapter 15, this volume.
VOC emissions measurements from feed,
animals and their waste have been completed
in environmental chambers (Shaw
et al
., 2007;
Sun
et al
., 2008), with transportable 'smog'
chambers (Howard
et al
., 2010a,b), and some
on-farm VOC measurements have used isola-
tion flux chambers, which limit the airflow over
the measured surfaces and likely do not accu-
rately represent emissions under 'normal' con-
ditions (Montes
et al
., 2010). Proper validation
for all of these various GHG and VOC emission
capturing systems and their gas analyser sys-
tems with known standards is paramount to
ensure the data are accurate. Furthermore, col-
lecting accurate emissions datasets is required
to develop and improve existing models that
can predict or simulate emissions from animal
agriculture. The numerous existing emissions
models and the strategies are beyond the scope
of this chapter but have been reviewed by
Archibeque
et al
. (2012). However, it is impor-
tant to note that our current understanding
of all of the bio-geochemical processes that
lead to GHG and VOC emissions is limited, and
Measurement and Modelling
of Emissions
Central to both the estimation of 'baseline' emis-
sions inventories, or the testing of GHG or VOC
