529
regulator for water vapour in the atmosphere and is thus the determining factor in
the equilibrium temperature of the earth and therefore global warming [5].
The gradual increase in the overall temperature of the atmosphere (global warming) has led to the following changes in the earth’s climate conditions [6]:
• Increase in temperature of the upper layers of the oceans.
• Increase in sea levels.
• Decrease in oxygen (O 2 ) concentration in the oceans.
• Increased acidification of surface waters.
• Increased loss of ice from glaciers.
• Increased incidence of extreme weather and climate events such as heat waves,
flooding, storms.
All these observations and trends emphasize the need to deal with the carbon
dioxide being emitted into the atmosphere. We need to understand the earth’s carbon cycle and carbon dioxide emission sources. Although eliminating anthropogenic sources of CO 2 emissions by eliminating fossil fuel usage is the best alternative,
by all practical estimations the transition to renewable sources of energy will take at
least a decade. The carbon cycle and CO 2 emission sources are subsequently
discussed.
1.2 Carbon Cycle on Earth
The global carbon cycle can be viewed as a series of reservoirs of carbon in the earth
system, which are connected by exchange fluxes of carbon [3]. Figure 1 shows the
global carbon cycle in the earth system. The earth system consists of three reservoirs: ocean, land, and atmosphere. CO 2 is the dominant carbon species in the atmosphere. On the land reservoir, carbon is found as organic compounds in vegetation,
dead organic matter in soils and fossil fuel reserves in the subsurface. In the ocean,
carbon occurs predominantly as dissolved inorganic carbon, dissolved organic carbon and in ocean floor sediments. The marine biota, predominantly phytoplankton,
and other microorganisms represent a small organic carbon pool. Carbon is transferred from one reservoir to another through carbon fluxes denoted by arrows
in Fig. 1.
Carbon fluxes between the atmosphere and the ocean surface (ocean atmosphere
gas exchange) arise by the partial CO 2 pressure difference between the air and the
sea while carbon fluxes between the atmosphere and land are mainly due to photosynthesis, respiration, and in the industrial era, fossil fuel combustion and net land
use change.
Figure 1 clearly shows that before the industrial era, the carbon fluxes between
the atmosphere and the other reservoirs (land and ocean) were essentially in balance
such that on the average carbon dioxide concentration in the atmosphere was steady.
Before the industrial era, the carbon fluxes were only by natural processes. In the
industrial era, new sources of CO 2 emission (fossil fuel combustion and net land use
Synthesis of Novel Catalysts for Carbon Dioxide Conversion to Products of Value
regulator for water vapour in the atmosphere and is thus the determining factor in
the equilibrium temperature of the earth and therefore global warming [5].
The gradual increase in the overall temperature of the atmosphere (global warming) has led to the following changes in the earth’s climate conditions [6]:
• Increase in temperature of the upper layers of the oceans.
• Increase in sea levels.
• Decrease in oxygen (O 2 ) concentration in the oceans.
• Increased acidification of surface waters.
• Increased loss of ice from glaciers.
• Increased incidence of extreme weather and climate events such as heat waves,
flooding, storms.
All these observations and trends emphasize the need to deal with the carbon
dioxide being emitted into the atmosphere. We need to understand the earth’s carbon cycle and carbon dioxide emission sources. Although eliminating anthropogenic sources of CO 2 emissions by eliminating fossil fuel usage is the best alternative,
by all practical estimations the transition to renewable sources of energy will take at
least a decade. The carbon cycle and CO 2 emission sources are subsequently
discussed.
1.2 Carbon Cycle on Earth
The global carbon cycle can be viewed as a series of reservoirs of carbon in the earth
system, which are connected by exchange fluxes of carbon [3]. Figure 1 shows the
global carbon cycle in the earth system. The earth system consists of three reservoirs: ocean, land, and atmosphere. CO 2 is the dominant carbon species in the atmosphere. On the land reservoir, carbon is found as organic compounds in vegetation,
dead organic matter in soils and fossil fuel reserves in the subsurface. In the ocean,
carbon occurs predominantly as dissolved inorganic carbon, dissolved organic carbon and in ocean floor sediments. The marine biota, predominantly phytoplankton,
and other microorganisms represent a small organic carbon pool. Carbon is transferred from one reservoir to another through carbon fluxes denoted by arrows
in Fig. 1.
Carbon fluxes between the atmosphere and the ocean surface (ocean atmosphere
gas exchange) arise by the partial CO 2 pressure difference between the air and the
sea while carbon fluxes between the atmosphere and land are mainly due to photosynthesis, respiration, and in the industrial era, fossil fuel combustion and net land
use change.
Figure 1 clearly shows that before the industrial era, the carbon fluxes between
the atmosphere and the other reservoirs (land and ocean) were essentially in balance
such that on the average carbon dioxide concentration in the atmosphere was steady.
Before the industrial era, the carbon fluxes were only by natural processes. In the
industrial era, new sources of CO 2 emission (fossil fuel combustion and net land use
Synthesis of Novel Catalysts for Carbon Dioxide Conversion to Products of Value