Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 299

one electron per Fe 3+ , only the amount of sulfate
reduced perfectly matched the quantity of meth-
ane which was not produced under inhibition.
FRB also participates in the oxidation of electron
donors other than acetate and H 2 , thus limits its
properties of reduction in methanogenesis. This
may be another reason for the lower effi ciency of
inhibition of methanogenesis under ferrihydrite
amendment. It was also demonstrated by Lueders
and Friedrich ( 2002 ) that although the mitigating
agent such as gypsum is added in the soil about
one-tenth that of the ferrihydrite amendment, still
the mitigation effects were comparable: 69 % and
85 % methane reduction, respectively.
(i) Advantage
• Methane emissions can be reduced.
(ii) Disadvantage
• The approach is still at the experimental
stage.
The technologies of conservation tillage, mid-
season drainage, and alternate fl ooding reduced
GHG emissions without extra expenditure.
Higher net return with these technologies sug-
gests the tremendous potential scope of their
adoption by farmers.
Water management is often considered a good
strategy to mitigate methane emissions from rice
fi elds. Water-saving technologies can reduce
methane emissions in a given area of rice land.
The saved water will then be used to irrigate
more land and new crops in future seasons. Rice
is grown on more than 140 million hectares
worldwide. Ninety percent of rice fi elds are tem-
porarily fl ooded, providing scope for better water
management to reduce water consumption,
related energy and electricity consumption, and
fertilizer consumptions. These reductions would
result in methane mitigation and could then be
included for claiming carbon credits.

source of pollution and a threat to aquifers and
surface waters. Animal manures can release sig-
nifi cant amounts of N 2 O and CH 4 during storage.
Methane emissions from manure stored in
lagoons or tanks can be reduced by cooling, use
of solid covers, mechanically separating solids
from slurry, or by capturing the CH 4 emitted.
Economic growth and changing lifestyles in
some developing countries are causing a growing
demand for meat and dairy products, notably in
China where current demands are low.
The most known technology for manure man-
agement is the anaerobic digestion, which is a
process in which organic matter from wet organic
wastes (i.e., liquid manure) is converted into
methane by bacteria in the absence of oxygen
(Fig. 13.11 ). The methane is then collected and
may be used to generate electricity. In addition,
the anaerobic digestion process creates poten-
tially valuable by-products, such as the solids
fraction - fi ber - and liquid with available
nutrients.
Another common technique is the aerobic
digestion, which is useful in treating liquid
manure for odor reduction, chemical oxygen
demand (COD) and biochemical oxygen
demand (BOD) reduction, and pathogen con-
trol. Aerobic treatment is usually a batch pro-
cessor, semicontinuous (batch feed). In a batch
process, all of the treated material is removed
from the facility before refi lling with untreated
slurry. In a batch feed or semicontinuous pro-
cess, some of the treated material is displaced
by the addition of untreated material to the
digester (Fig. 13.12 ).
A third method widely applied in the agricul-
tural sector worldwide is composting, which is an
aerobic digestion process used for solid wastes.
Slurries or separated solids can be composted if
mixed with a carbon source such as straw, peat, or
wood shavings. However, composting slurry
without separating the solids requires a great deal
of additional material to retain the liquid. This
would be very impractical due to the cost of the
material and the energy required to turn the com-
post. Composted manure is a premium organic
fertilizer and holds some potential as a marketable
product in the gardening and landscaping market.

13.1.6 Manure Management

Livestock manures represent a valuable resource
that, if used appropriately, can replace signifi cant
amounts of chemical fertilizers. However, unless
animal manure is managed carefully to minimize
odor, nutrient losses, and emissions, it becomes a