Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 311

the air by leguminous plants has a mitigation
potential that amounts to 4.5-6.5 Gt CO 2 e year −1
(out of 50 Gt CO 2 e year −1 global GHG emissions)
or about 9-13 % of the total GHG emissions. The
mitigation is accomplished by sequestering C in
soils due to intensive humus production (Smith
et al. 2007 ). Regular applications of livestock
manure can induce substantial increases in soil
organic carbon over the course of a few years
(Lal et al. 1998b ). Organic agriculture has lower
N 2 O emissions, i.e., 1.2-1.6 Gt CO 2 e year −1 . In
organic agriculture, biomass is not burned. It
reduces the N 2 O emissions by 0.6-0.7 Gt CO 2 e
year −1 in comparison to conventional agriculture
(Smith et al. 2007 ). Organic systems are highly
adaptive to climate change due to:
• Application of traditional skills and farmers'
knowledge
• Soil fertility-building techniques
• High degree of diversity
Organic farming could considerably reduce
the GHG emissions of the agriculture sector and
make agriculture almost GHG neutral (Niggli
et al. 2009 ). Greenhouse gas emissions due to the
applications of synthetic fertilizers are estimated
to be 1,000 million tons annually. These emis-
sions would not occur using an organic approach.
GHG emissions of agriculture would be reduced
by roughly 20 %. Another 40 % of the GHG
emissions of agriculture could be mitigated by
sequestering carbon into soils at rates of 100 kg
of C ha −1 year −1 for pastureland and 200 kg of C
ha −1 year −1 for arable crops. By combining
organic farming with reduced tillage, the seques-
tration rate can be increased to 500 kg of C
ha −1 year −1 in arable crops as compared to plowed
conventional cropping systems, but as the soil C

dynamics reach a new equilibrium, these rates
will decline in the future. This would reduce
GHG emissions by another 20 %. Organic farm-
ing is an important option in a multifunctional
approach to climate change.

13.2 Livestock Management

Ruminant animals have a unique digestive
system. Ruminants possess a rumen, or large
fore-stomach, in which microbial fermentation
breaks down coarse plant material for digestion.
Nonruminant domesticated animals (e.g., swine,
horses, mules) also produce CH 4 emissions
through enteric fermentation, although this
microbial fermentation occurs in the large intes-
tine, where the capacity to produce CH 4 is lower
(USEPA 2005 ). Enteric fermentation enables
ruminants to eat plant materials but also produces
CH 4 , a potent greenhouse gas that contributes to
global climate change. During digestion,
microbes present in an animal's digestive system
ferment food consumed by the animal. This
microbial fermentation process is referred to as
enteric fermentation and produces CH 4 as a by-
product, which can be exhaled or eructated by the
animal. The amount of CH 4 produced and
excreted by an animal depends primarily on the
animal's digestive system and the amount and
type of feed it consumes. In fact, with an emis-
sion of approximately 140.8 Tg CO 2 eq in 2008,
enteric fermentation accounts for about 2 % of
the total US emissions in 2008 (EPA 2010 )
In Table 13.11 , the enteric fermentation emis-
sions within the USA are displayed per livestock
type. In the USA, beef cattle are by far the largest

Table 13.11 CH 4 emiss ions from enteric fermentation per livestock type (EPA 2010 )

CH 4 emissions from enteric fermentation per livestock type (Tg CO 2 eq.)
1990 Livestock type 1995 2000 2005 2008

Beef cattle 94.5 107.7 100.6 99.3 100.8

Dairy cattle 32.0 30.5 30.9 30.6 33.1

Horses 1.9 1.9 2.0 3.5 3.6

Swine 1.7 1.9 1.9 1.9 2.1

Sheep 1.9 1.5 1.2 1.0 1.0

Goats 0.3 0.2 0.3 0.3 0.3

Total 132.4 143.7 136.8 136.7 140.8