Decarbonisation Technology - February 2022 Issue

The Spanish oil major Repsol is investing €2.549 billion in a project to build one of the world’s largest facilities to manufacture net-zero emissions fuels using CO 2 captured from the Petronor refinery and green hydrogen generated with renewable energy, as well as pyrolysis of urban waste from the city of Bilbao (Repsol, 2020). As one of its strategic pillars to achieve net-zero emissions by 2050, Repsol plans to install 1.9 GW of green hydrogen capacity (Repsol, 2021). The company will use different technologies to reach its renewable hydrogen production targets, including electrolysis, biogas production, and photo electro catalysis. The main advantage of photo electro catalysis technology over current solutions is that only water and sunlight are needed as raw materials to produce 100% renewable hydrogen. Currently, 90% of all hydrogen produced is used in the industrial sector as a raw material in refining, ammonia production, and others. For this reason, the EU envisages the deployment of renewable hydrogen to decarbonise industrial sectors where electrification is not an alternative in the short to medium term. Hydrogen is also essential in the production of liquid fuels with a low carbon footprint, such as biofuels and synthetic fuels. The advantage of these products over other options is that their performance is similar to traditional fuels. Enhanced weathering is a carbon capture process that could remove over 2 Gt CO 2 each year. Houlton describes the results of experiments at a 50 acre site in California, the world’s largest demonstration project, and explains: “Silicate minerals exposed to the weather have been sequestering atmospheric carbon and turning it into rock since the dawn of time, but it’s a process that normally takes thousands of years” (Houlton, 2020). This period can be cut to two years by grinding silicate rocks into a fine powder, thus increasing its surface area and its contact with CO 2 . As a further step, spreading the rock dust on crop lands gives it immediate contact with CO 2 as it is produced by plant roots and soil microbes. The minerals also increase farm yields, providing farmers with an incentive (along with negative emissions credits) to become a link in this carbon capture chain. CO 2 transport and storage The availability of infrastructure to transport CO₂ safely and reliably is an essential factor for the deployment of CCUS. Large-scale transport of CO₂ is done via pipeline or ship, although for short

carbonation process self-sufficient, (Khoo, et al., 2011). Gálvez-Martos et al., have studied a life cycle and eco-efficiency assessment of a novel construction material based on MgCO 3 3H 2 O (nesquehonite), which has a similar cementitious behaviour to gypsum plaster (Galvez-Martos, et al. , 2021). The material produces fewer CO 2 emissions than conventional gypsum plasterboard. The eco- efficiency is highly dependent on the alkali used for CO 2 capture. Hills et al . reviewed mineralisation process in geologically derived minerals and industrial wastes, with a focus on the manufacture of products with value. An assessment of mineralised construction aggregates suggests that CCUS technology can manage significant quantities of CO 2 (Hills, et al., 2020). The manufacture of carbonated aggregates is commercially established in Europe, and recent advances in technology include a mobile plant that directly utilises flue gas derived CO 2 in the mineralisation process. Green chemistry paths and CCUS Researchers at Oregon State University have made a key advance in the green chemistry pursuit of converting CO 2 into reusable forms of carbon via electrochemical reduction. They have shown that a new type of electro-catalyst can selectively promote a CO 2 reduction reaction to carbon monoxide (Song, et al ., 2019). “In contrast to traditional CO 2 reduction that uses chemical methods at high temperatures with a high demand of extra energy, electrochemical CO 2 reduction reactions can be performed at room temperature using liquid solution”. Feng et al found that nickel phthalocyanine catalyst at high current densities improved the efficiency of conversion to carbon monoxide in a gas diffusion electrode device. Song et al., have reviewed and summarised major strategies and technologies for CO 2 capture from fossil fuel combustion and simultaneously the characteristics of cryogenic technologies for CO 2 capture (Song, et al. , 2019). The existing challenges that need to be overcome in cryogenic technology include cold energy sources, capture costs, and impurities. The results of this investigation indicated that cryogenic CO 2 capture processes can be easily retrofitted to the existing industrial emission facilities and avoid the challenges associated with chemical solvents or physical sorbents, with the remark that opportunities exist for the future development of cryogenic-based technologies’.