Summary
Carbon dioxide (CO2) capture and usage (CCU) is currently a global topical issue, and is viewed as one possible route to reduction of CO2 concentrations in the atmosphere. The core issues facing the world in current times—development, economy, and environment—are identified as being dependent on the provision of clean, efficient, affordable, and reliable energy services. Currently, the world is highly dependent on fossil fuels for provision of energy services, and the amount of which renewable energies can sufficiently replace is minimal.
The deployment of appropriate CO2-separation technologies for the processing of natural gas is viewed as an abatement measure toward global CO2-emissions reduction. Selection of the optimum technology among the several separation technologies for a particular separation need requires special attention to harness the economic and environmental benefits. The captured CO2 would also require appropriate disposal or usage so as to sequester or “delay” its re-entry into the atmosphere. These challenges of CCU— involving natural gas particularly during processing, which has become an area of intense research—shall be discussed in the paper with respect to the selected technique for CO2 capture. A typical natural- gas-production scenario in Nigeria shall be analyzed for potential CO2 capture. Further discussion shall be on the identification of the recovered CO2 gas-usage framework, such as CO2 flooding [in enhanced oil recovery (EOR)], for additional revenue generation, assessment of the CO2 savings, and the contribution to the clean development mechanism (CDM).
Introduction
The separation of CO2 from the gas stream is currently a global issue. The increasing amounts of greenhouse gases (GHGs) in the atmosphere in recent years, considered to be partly responsible for climate change, have been a serious global concern, and CO2 gas has been identified to as a major contributor of GHGs. Several postulations have proposed a long-term global stabilization of CO2 concentrations in the atmosphere to be a possible panacea for curtailing climate change and global warming. The use of fossil fuels inclusive of natural gas currently dominate the source of global energy supply, which are considered capable of meeting the world’s increasing energy needs up to 84% by 2030 (IEA 2008, page 47) from the current demand of approximately 81% (IEA 2012, page 10). CO2 emission to the atmosphere from combustion of fossil fuels (coal, oil, and natural gas) and during production/processing of natural gas is considered to be the major cause of high CO2 volumes in the atmosphere.
It has been outlined that energy scenarios involving the use of clean energy technologies can result in a more than 50% reduction in global CO2 emissions up to 2050 (IEA 2010) with the deployment of carbon capture and sequestration (CCS), inclusive of industry and power generation, as capable of contributing up to 19% in CO2 reductions (IEA 2008, page 69). These are not withstanding the assessment performed by IEA (2012) with respect to “high potential CO2 emissions” found with global “carbon reserves,” and thereby outlining the deployment of CCS as the major technology required for sustaining the projected demand on fossils. “The assessment has attributed almost 63% to coal, 22% to oil and 15% to gas in CO2 emissions potential locked in these reserves.” The case of CO2 in natural gas represents a typical scenario for a number of oil and gas companies faced with the enormous challenge of reduced energy level of sales gas making it subquality or when disposal by flaring increases the source of CO2 emissions to the atmosphere. However, the amount of natural gas flared globally has been shown to contribute approximately 1.2% of the global CO2 emissions, which is given to be more than one-half of the certified emissions reductions under the Kyoto Protocol (ICF International 2006).
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