Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 304

Additionally, by decreasing the surface area of
the manure heap and by timely transport of
manure to an enclosed storage chamber, the
amount of NH 3 and CH 4 emissions can be reduced
effectively (Weiske et al. 2006 ).
Generally, reducing ammonia volatilization
and preventing odor can be achieved by covering
liquid manure with straw, which may also
increase methane emissions. Berg and Pazsiczki
( 2006 ) achieved GHG emission reductions by
combining straw coverage with an acidizing
technique. Experimental results showed that
methane emissions were reduced by 40 % by
adjusting the pH value of liquid manure to less
than 6 with lactic acid and integrated covering
with straws.
A hard crust is naturally formed during the
storage of manure, which prevents ammonia
produced by manure from escaping. An experi-
ment by Smith et al. ( 2007 ) showed that ammo-
nia emissions from manure with naturally
formed crust can be reduced by over 60 % com-
pared to the emissions from manure without the
crust. Besides slowing ammonia loss, the hard
crust on manure slurry also reduces methane
emissions. Petersen and Ambus ( 2006 ) proved
that methane-oxidizing bacteria exist in the hard
crust of manure slurry, which oxidize methane
into CO 2 , thus achieving an emission reduction
because methane is a more potent greenhouse
gas than CO 2 . When the concentration of meth-
ane is 500-50,000 ppmv, the amount of emission
reduction by methane-oxidizing bacteria is
1-4.5 g CH 4 m −2 days −1 (Petersen and Ambus
2006 ).
Permeable covers are less expensive than
impermeable covers, but they do not last as long
and are not as effective at reducing the emissions
of odors and gases. However, they can provide
reductions in odor, ammonia, and hydrogen sul-
fi de emissions from manure storage facilities. A
wide variety of organic and man-made materials
have been utilized to construct permeable covers
with variable results.
If impermeable covering materials are
adopted, then the mass transfer between manure
with the outside is cut off. Meanwhile, an anaero-
bic environment is created within the manure,

promoting the generation of methane. Then gas
collection devices can be installed to capture
methane for cooking and heating purposes. In
addition, the use of covering materials can effec-
tively prevent the emission of nitrogen containing
gases such as ammonia, thereby retaining nutri-
ents in the manure. After a period of storage, it
can be applied onto farmland as organic
fertilizer.

13.1.7 Agro-forestry (Mitigation)

Agro-forestry is the production of livestock or
food crops on land that also grows trees for tim-
ber, fi rewood, or other tree products. It includes
shelterbelts and riparian zones/buffer strips with
woody species. The standing stock of carbon
aboveground is usually higher than the equivalent
land use without trees, and planting trees may
also increase soil carbon sequestration. But the
effects on N 2 O and CH 4 emissions are not well
known.
Agro-forestry, as defi ned by the World
Agroforestry Centre, is “a dynamic, ecologically
based, natural resources management system
that, through the integration of trees on farms and
in the agricultural landscape, diversifi es and sus-
tains production for increased social, economic,
and environmental benefi ts for land users at all
levels.” On the other hand, the Association for
Temperate Agroforestry describes it as “an inten-
sive land management system that optimizes the
benefi ts from the biological interactions created
when trees and/or shrubs are deliberately com-
bined with crops and/or livestock” (IGUTEK
2011 ). Agro-forestry offers great potential for
carbon sequestration (UNFCCC 2008 ).
Terrestrial sequestration is based on the fact
that plants take CO 2 out of the atmosphere
through photosynthesis and store it as organic
carbon in aboveground biomass (trees and other
plants) and in the soil through root growth and
the incorporation of organic matter (Fig. 13.13 ).
Thus, the process of carbon loss through land-
use change can be reversed, at least partially,
through improved land-use and management
practices. In addition to afforestation, changes in