Quantitative Measurements of Ammonia and Methane Loss from Livestock - Sustainable Animal Agriculture - page 240

emission is 12-17% of the global CH 4 source,
whereas an earlier estimate by Moss et al . (2000)
indicated enteric CH 4 was 12% of the global,
19% of the anthropogenic and 36% of the agri-
cultural CH 4 emissions. Steinfeld and Wassenaar
(2007) reviewed carbon and nitrogen emissions
from livestock (by region) and concluded that
livestock accounted for 18% of global GHG
emissions (i.e. global warming effect) and that
livestock enteric CH 4 losses were 'the most impor-
tant source of anthropogenic CH 4 emissions' at
86 Mt year −1 . In a recent review, O'Mara (2011)
reported on EPA data (EPA, 2006) that show the
enteric CH 4 from ruminants is 89% of the enteric
plus manure CH 4 emissions (1929 versus total
livestock CH 4 emissions of 2164 Mt of CO 2 -
equivalent per year).
The emission of CH 4 by ruminants is a loss
of energy from the feed that could otherwise be
utilized by the animal, and accounts for 2-12%
of the gross energy content of the feed as
reported by Johnson and Johnson (1995). The
range in emissions is due mainly to the level of
feed intake and the composition of the diet (Moss
et al ., 2000; Benchaar et al ., 2001). In addition

to environmental effects, enteric CH 4 emissions
also have direct economical implications for the
producer in terms of energy feed efficiency.

Techniques for Monitoring Ammonia
and Methane Emissions

There are many techniques available to quantify
the emission of CH 4 from enteric fermentation in
ruminants (Table 15.1) and CH 4 and NH 3 from
manure (Tables 15.2 and 15.3, respectively).
The techniques for enteric CH 4 include both
in vitro (not reported in this chapter) and in vivo
techniques, where in vivo methods encompass
the use of enclosures (masks, hoods, whole-
animal chambers and tunnels), tracer gases
and micrometeorological measurements. For
NH 3 the techniques generally used include
enclosures and micrometeorological measure-
ments. The technique of boundary layer budget-
ing (Harper et al ., 2011) is not included in this
chapter since it applies to a regional scale and is
beyond the scope of this review.

Table 15.1. Examples of enteric methane emissions for beef cattle, dairy cows and sheep measured
using different techniques. Emissions under the same study are direct comparisons of techniques.

Methane emission
(g per animal per day) Ruminant Technique Study

Beef cattle ≈ 138-155 NSS Tomkins et al . (2009)

Beef cattle 136 BLS Tomkins et al . (2011)

114 FT-SS chamber

Beef cattle 86-180 (young heifers) Tracer - enteric DeRamus et al . (2003)

165-294 (mature cows)

Beef cattle 209-242 (different sensor) BLS Laubach et al . (2008)

167 FG

182 MB

Dairy cows 296 (dry)-438 (lactating) FT-SS chamber Sun et al . (2008)

Dairy cows 369-374 Tracer - enteric Foley et al . (2009)

Dairy cows 297 (pens) BLS Bjorneberg et al . (2009)

325 (pens and lagoon)

Dairy cows 299 BLS Gao et al . (2011)

Sheep 16-18 (2- and 1-h sample) NSS Goopy et al . (2011)

Sheep 43-66 FT-SS chamber Liu et al . (2011)

Sheep 14-19 FT-SS face mask Wang et al . (2007)

Sheep ≈ 14 FT-SS tunnel Lockyer and Champion

(2001)

Sheep 20 EC Dengel et al . (2011)

NSS, non-steady-state; BLS, backward-time Lagrangian stochastic; FT-SS, flow-through steady-state; FG, flux gradient;
MB, mass balance; EC, eddy covariance. ≈ , Preceding values indicates units were converted for use in this table using
the ideal gas law.