A review of atmospheric carbon dioxide sequestration pathways; processes and current status in Nigeria

Increased world energy demand due to population and rapid technological growth, and urbanisation has induced climatic change through increased atmospheric greenhouse gas (GHG) concentration, of which the atmospheric Carbon Dioxide Removal (CDR) strategies have been identified as the pertinent pathway towards the reduction of this GHG. These CDRs serve as an adaptation and mitigation approach to abate the impacts of climate change. Different CDR strategies are encapsulated in the term Carbon sequestration, describing natural and technological approaches by which carbon dioxide (CO2) is removed from the atmosphere. Technologically, Carbon Capture Use and Storage (CCUS) is a CDR strategy that encompasses both carbon capture and storage (CSS) and carbon capture and utilisation (CCU) technologies. Its developmental pathways and implementation depend on understanding the natural carbon source and sink contained in the natural carbon cycle and CO2 capture technology. CCS technologies capture CO2 from large point sources, mainly power plants and industrial processes and store it in underground geological formations that include the deep saline aquifer, depleted oil and gas reservoirs, unminable coal seams and oceanic basaltic formations. The captured CO2 is also stored through in-situ mineral carbonation and direct ocean injection. Other processes that enhance CO2 removal include ocean fertilisation, ocean alkalinity enhancement and marine/terrestrial photosynthetic conversion, which stores CO2 in the pedosphere or surface ocean relative to natural carbon sequestration. CCU is a CCS complimentary technology that converts the captured CO2 into value-added products through CO2- ex-situ mineralization, value-added storage (enhanced oil/gas recovery, enhanced geothermal system, and enhanced coalbed/shale gas recovery) and CO2- chemical feedstock and biofuels. At present, there is no CCUS project in Nigeria. However, different preliminary site characterisation studies have been carried out for CCUS project development, which is being delayed by a lack of funding, robust policies, and public awareness.