Decarbonisation Technology - February 2022 Issue

to gasification plants in which the fuel (e.g., coal, biomass) is converted to gaseous components prior to combustion; it concentrates the levels of CO 2 to greater than 40%. In oxy-combustion, relatively pure oxygen is used and produces CO 2 at levels of about 60%. The advantage of both of these processes is that CO 2 is produced in significantly higher concentrations than with post- combustion capture processes, making capture much more efficient. In all three strategies, CO 2 must be efficiently separated from other gaseous components and water vapour for subsequent sequestration or conversion. While CO 2 capture is relatively easy with oxy-combustion, the process requires the ability to separate oxygen from air at low cost (Jiang & Ashworth, 2021). The science and technologies supporting CCUS has advanced over the last decade, yet opportunities remain for reducing costs, improving performance, creating better business and regulatory models, and discovering new uses for CO 2 . This article screens recent unique scientific publications/articles related to CCUS and presents an assessment of the ongoing innovative researches and their translation into low cost efficient technological solution towards reduction in carbon emissions. alternatives, both of which start with the process of capturing the CO 2 . In CCU, the captured CO 2 is recycled for further use, whereas with CCS the captured CO 2 is compressed as pressurised gas for long-term storage or sequestration at geological sites. The two alternatives are considered to be one of the solutions critical in mitigating climate change (Cuellar-Franca & Azapagic, 2015), (IEA, 2020). While CCU has a lower capacity level than CCS for reducing CO 2 levels in the short term, it does nevertheless offer a route to reduce CO 2 emissions, as well as providing a process to develop value- added materials for further use as part of the circular economy paradigm. CCU value chain and supporting themes Hasan et al. developed a multi-scale framework for CCUS and CCU through a process of inductive reasoning and by a series of cross-cutting supporting basic themes. These represent different perspectives of CCU, namely: industrial, CCUS processes. CCUS is the combined term covering two

1. Burning of hydrocarbons for power generation. 2. Liquid fuels used for transportation. 3. Industrial processes. 4. Production of building materials. Source 1. Capture via pre-combustion, post combustion, oxy fuel or from industrial processes. 2. Sorbent, solvent-based and membrane separations technologies. Capture

1. Pipeline, road and rail options. 2. Transportation supply chain. 3. Economic and cost drivers. 4. Environmental, safety and risk factors. Transport

1. EOR and EGR. 2. Chemical conversion to feedstock materials (methane, methanol and urea). 3. Direct synthesis of CO based polymers. 4. Production of building materials. Utilisation

Figure 1 CCU value chain for the development of CCU technologies (Hasan , et al., 2015)

governmental and societal, as well as the ultimate objective to reduce CO 2 emissions and mitigate climate change. This multi-scale framework enables generalisation of findings from analysis of specific installations and it is possible to synthesise a value chain for development of CCU technologies (see Figure 1 ). The four main stages of the CCU value chain are the source, capture, transport, and utilisation stages, where each stage identifies key areas that require further R&D. It is envisaged that the value chain can guide future research trajectories on CCU and assist industry to evaluate CCU as part of the technology development and commercialisation process. Currently practiced carbon capture technologies – their limitations The workshop Carbon Capture: Beyond 2020 (Alivisatos & Buchanan, 2010) identified the following limitations: three main types of separation strategies are used – liquid absorbents,