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388 12 Carbon Capture and Storage

be achieved by conservation tillage, crop selection, rotation and intensified crop-
ping, managing soil biogeochemistry, and manipulation of microbial communities.
Tilling disturbs the soil resulting in reduced CO 2 storage. Therefore, reduced
tillage intensity contributes to increased CO 2 storage. It can be achieved by no till,
ridge till, minimum till, and mulch till. Conservation tillage aims at the reduction of
soil erosion and the maintenance of water-holding capacity of soils. It is expected to
restore the loss of CO 2 that was released by historical intensive tillage practice over
a short period of time.
Crop selection, rotation, and intensified cropping allow more above-ground
biomass, and consequently enable more CO 2 storage. Their net carbon storage
effects will be maximized when applied in conjunction with conservation tillage.
Soil organic carbon may depend on the soil biological and chemical properties,
for example, pH. Addition of metal oxides such as CaO and MgO is expected to
enhance the chemical sorption of CO 2 into the soils. However, this change in pH
may also change the behaviors of microorganisms in the soils.
Fungal and bacterial species in the soils play an important role in the release and
storage of soil organic carbon as well as the emissions of other GHGs such as N 2 O
and CH 4 . The complexity of microbial community opens another opportunity for
potential CO 2 storage and/or reduced GHG emissions by multiplication of the
microbial species. Different ongoing research projects are being conducted to
evaluate the feasibility of this approach.

12.8.5.2 Change in Land Use

Land on the earth can be grouped into, in the increasing order of carbon storage
share, degraded land < croplands < pasture < grass lands < wetlands < forest. Land
upgrading in terms of carbon storage capacity is expected to contribute to additional
CO 2 storage. IPCC (2000) report on land use, land-use change and forestry esti-
mated that about 1 Gt-C per year could be stored in the short term as a result of the
regrowth of perennial vegetation and improvements of land management practices
in croplands, grasslands, and forests. For example, change in land use can be
achieved by wetland management and restoration and forestry management,
afforestation, and reforestation.
Protection and restoration of wetlands presents an opportunity for increased
underground organic carbon storage. The residence time of the CO 2 stored in
wetland depends on the plant type and the degree of inundation. Since wetland is
the second best land in terms of CO 2 storage, only after forest, more CO 2 is released
into the atmosphere when wetland is drained for uses as agricultural or urban and
industrial development. Unfortunately, recent research shows that it is challenging
to restore the lost CO 2 simply by recreating wetlands. More research and devel-
opment is needed in this area.
The loss of CO 2 storage in forest can be reduced by reducing logging and
deforestation. Protection of old trees and regeneration of secondary and degraded