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processes that transform carbon dioxide from an energy or industrial sector byproduct to a useful commodity. When compared to capture and sequestration, CO 2
utilization for chemical synthesis presents several benefits beyond the reduction of
emissions. These benefits include the recycle of CO 2 as a feedstock for synthesis,
the reduction in the depletion of fossil fuels, possible reduction in other environmental impact categories (eutrophication, terrestrial acidification, photochemical
oxidant formation, particulate matter formation) for the process, and increased profitability from synthesised products [15, 16]. Several processes are presently available for the utilization of captured carbon dioxide.
2.1 Enhanced Oil Recovery
Captured CO 2 is compressed and injected into depleted oil and gas reservoirs where
they facilitate the recovery of residual oil and gas by providing the driving force for
oil and gas recovery. The carbon dioxide displaces the hydrocarbons from the reservoir, and the CO 2 is safely sequestered in the reservoir. Carbon dioxide has been
used for enhanced oil recovery for many decades, and several large-scale EOR projects are in operation in North America [14].
2.2 Photo-Catalytic Conversion of CO 2
This process is also referred to as artificial photosynthesis as it has similarities with
natural photosynthesis in plants as it is based on using solar energy to reduce CO 2
into various chemical products and fuels. Photocatalytic CO 2 conversion makes use
of semi-conductors to promote reactions in the presence of light irradiation.
Photocatalytic materials that have been explored as catalysts include metal oxides
and metal organic frameworks (MOF). The basic process can be summarized into
three steps: (1) generation of charge carriers (electron–hole pairs) upon absorption
of photons with suitable energy from light irradiation, (2) charge carrier separation
and transportation, (3) chemical reactions between surface species and charge carriers. Photo-catalytic conversion of CO 2 has been shown to yield hydrocarbons such
methane, synthesis gas, formaldehyde, formic acid and methanol [17, 18].
2.3 Bio-conversion of CO 2
These processes involve the use of micro-organisms such as algae to convert CO 2
into biofuels. Algae require CO 2 to grow and many algae species produce oil and
other bio-refinable products which can be used as bio-fuels. In algae, the fixation of
CO 2 occurs due to two separate reaction steps. In the light-dependent set of
O. Okonkwo and P. Biswas
processes that transform carbon dioxide from an energy or industrial sector byproduct to a useful commodity. When compared to capture and sequestration, CO 2
utilization for chemical synthesis presents several benefits beyond the reduction of
emissions. These benefits include the recycle of CO 2 as a feedstock for synthesis,
the reduction in the depletion of fossil fuels, possible reduction in other environmental impact categories (eutrophication, terrestrial acidification, photochemical
oxidant formation, particulate matter formation) for the process, and increased profitability from synthesised products [15, 16]. Several processes are presently available for the utilization of captured carbon dioxide.
2.1 Enhanced Oil Recovery
Captured CO 2 is compressed and injected into depleted oil and gas reservoirs where
they facilitate the recovery of residual oil and gas by providing the driving force for
oil and gas recovery. The carbon dioxide displaces the hydrocarbons from the reservoir, and the CO 2 is safely sequestered in the reservoir. Carbon dioxide has been
used for enhanced oil recovery for many decades, and several large-scale EOR projects are in operation in North America [14].
2.2 Photo-Catalytic Conversion of CO 2
This process is also referred to as artificial photosynthesis as it has similarities with
natural photosynthesis in plants as it is based on using solar energy to reduce CO 2
into various chemical products and fuels. Photocatalytic CO 2 conversion makes use
of semi-conductors to promote reactions in the presence of light irradiation.
Photocatalytic materials that have been explored as catalysts include metal oxides
and metal organic frameworks (MOF). The basic process can be summarized into
three steps: (1) generation of charge carriers (electron–hole pairs) upon absorption
of photons with suitable energy from light irradiation, (2) charge carrier separation
and transportation, (3) chemical reactions between surface species and charge carriers. Photo-catalytic conversion of CO 2 has been shown to yield hydrocarbons such
methane, synthesis gas, formaldehyde, formic acid and methanol [17, 18].
2.3 Bio-conversion of CO 2
These processes involve the use of micro-organisms such as algae to convert CO 2
into biofuels. Algae require CO 2 to grow and many algae species produce oil and
other bio-refinable products which can be used as bio-fuels. In algae, the fixation of
CO 2 occurs due to two separate reaction steps. In the light-dependent set of
O. Okonkwo and P. Biswas