Decarbonisation Technology - February 2022 Issue

can then be used to enrich agricultural lands and fix carbon by keeping carbon in soil for years. The sequestered CO 2 will stay in soil for hundreds of years by carbon burial, preventing the return of biotic carbon to the atmosphere via decomposition and therefore serving as a carbon sink. Cornell University has done field trials in several countries. An important area for further study is the interaction of bio-char with various soils across the world, including its application as nutrient and/or soil enhancement and also the mean CO 2 residence time in soil.  Ocean liming (OL) This process stores naturally captured CO 2 from the atmosphere in the oceans as bicarbonate ions. In this process, limestone is first extracted and calcined, during which the generated CO 2 is captured using available methods e.g. post-combustion capture scrubbers. The produced calcium oxide is then shipped to the ocean and directly dispersed in large scale. The resulting increase in the pH of the surface water leads to a rapid absorption of the atmospheric CO 2 . Future research is needed on large distribution of lime across the whole ocean, which can pose major intervention into the natural balance of the environment by way of ocean acidification and disturbance of ecosystems, before being applied commercially.  Soda/lime process In this technology, an aqueous sodium hydroxide solution is used to directly capture CO 2 from the air in a conventional scrubbing column. The resulting sodium carbonate is passed through a causticiser and, finally, a calciner, in which CO 2 is regenerated for compression, transport, and storage. The overall effect of this process is, in fact, generating a concentrated CO 2 stream from very dilute CO 2 source i.e. atmospheric air. However, there are still energy related obstacles, which are yet to be addressed before it is implemented . Conclusion CCUS carries considerable strategic value as a climate mitigation option. It can be applied in a number of ways and across a range of sectors, offering the potential to contribute, directly or indirectly, to emissions reductions in almost all parts of the global energy system. Some specific strategic values are:  Carbon capture is common to both CCU and for CCS. Cost of capturing CO 2 has been one of the

main barriers, hence higher energy efficiency capture processes will remain one of the main priority research areas.  CCUS technologies are one of the essential pillars for climate mitigation alongside electrification, hydrogen, and sustainable bioenergy. CCUS accounts for nearly 15% of the cumulative reduction in emissions in the IEA’s Sustainable Development Scenario.  Chemical conversion of CO 2 to methane for the eventual purpose of enabling production of dimethyl ether via dry reforming has been developed (Shakel, et al., 2016). Furthermore, the dry reforming to convert CO 2 and methane to syngas is a raw material used for the eventual production of liquid fuels (Fan, et al., 2009) offers a potential route to remove the two main GHG gases from the atmosphere or from industrial processes.  After years of slow progress and insufficient investment, there is a new momentum, with interest in CCUS, stronger investment incentives towards R&D projects, commercial facilities, and climate targets.  CCUS technologies contribute to clean energy transitions in several ways: • Reducing carbon emissions into the atmosphere • CCUS can be retrofitted to existing power and industrial plants • A solution for some of the most challenging emissions sources • A cost-effective pathway for low carbon hydrogen production to meet current and future demand from new applications in transport, industry and buildings • Direct air capture technologies to remove CO 2 from the atmosphere.  CCU processes such as mineralisation as well as application to the production of building materials, such as concrete, are less developed due to a mix of technical and economic reasons. Although there has been some progress in the past 10-15 years, significant progress remains to be made. Above- ground CO 2 mineralisation is also being seen as an alternative to underground storage due to some potential for seismic activity caused by underground injection of CO 2 .

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