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[Display omitted] • The pH-swing cold capture chloralkali process improves energy efficiency threefold over the benchmark process. • Integrating pH-swing cold capture chloralkali in eFuel synthesis moves most of the energy consumption to the electrolyzer. • We attain ∼ 76 % carbon capture efficiency and 79.5 % overall process efficiency. Renewable Fuels of Non-Biological Origin (RFNBOs, a.ka. "eFuels") are drop-in replacements for fossil fuels in the "hard-to-abate" sectors, and utilise existing distribution and storage infrastructure, but suffer from low synthetic efficiency. In particular, the low efficiency and high energy consumption of hydrogen synthesis by freshwater electrolysis remains a problem to be addressed. In the current study, we explore the potential of saltwater electrolysis (chloralkali) for the synthesis of eFuels generally, and specifically eMethanol. The study explores the use of chlorinated water in carbonate-loop pH-swing "cold capture" of carbon dioxide, and the resulting synergetic integration of the chloralkali process in eFuel syntheses. Doing so eliminates the high energy consumption of the calciner and the slaker of the benchmarked carbonate-loop thermal-swing method. It is replaced with a spontaneous chemical process in which chlorine is neutralized in the presence of carbonates. This allows the simultaneous solution of "The Chlorine Problem" of saltwater electrolysis, and a lower overall energy consumption of direct air capture when combined with green hydrogen synthesis. The only limitation on the comparison is that a large amount of carbon dioxide is over-captured when using chloralkali. That is, the ratio of hydrogen generated to carbon dioxide captured is fixed by the stoichiometry of chloralkali and not that of the eFuel. This results in an excess of carbon captured and thus a carbon-negative eFuel. We examine one configuration of secondary revenue and use it to inform the marginal cost of CO 2 capture. In the system proposed by Aeon Blue Technologies (ABT), carbon dioxide is absorbed into caustic according to the standard method. Hydrogen gas is produced in a standard chloralkali electrolyzer, along with caustic for the contactor, and chlorine. Water oxidation by chlorine gives the strong acid, hydrochloric acid, and the weak acid, hypochlorous acid, which react directly with wet carbonate to release CO 2. H 2 and CO 2 react in a methanol reactor to produce eFuel. H 2 is the limiting reagent for eFuel synthesis, giving an excess of cold captured CO 2. Thus, the current study underscores significant advancements in renewable fuel synthesis, particularly eMethanol, and evaluates the carbon capture and energy efficiency of a novel method. The simulation indicates that the marginal energy cost for a tonne of CO 2 is ∼ 184kWh. This gives ∼ 76 % theoretical carbon capture efficiency and an overall process efficiency of 79.5 % (approximately a threefold improvement over the benchmark). The authors are unaware of a comparable method. The overall system yields a tonne of carbon-neutral e-methanol (eMeOH) while capturing an additional 3 tonnes of carbon dioxide, which means the modelled process captures over 300 % more carbon dioxide than is released upon combustion of the eFuel. In summary, this research contributes valuable insights into carbon-negative eFuel production, representing a significant scientific step in sustainable fuel production. [ABSTRACT FROM AUTHOR]

• Six alternative or low-carbon fuels are evaluated for the cement sector. • Average long-term marginal abatement costs range from −70 to 138 CAD/tCO 2 e. • Up to 21% of emissions to 2050 can be eliminated with negative abatement costs. • Energy prices are the primary factor driving scenario cost performance. Limiting global warming and the pursuit of a net-zero global society by 2050 emphasizes the need to transform the hard-to-abate industrial sectors. The cement sector is the second-largest source of global industrial emissions, accounting for 8% of worldwide greenhouse gas emissions. Fuel switching in the cement sector is a decarbonization pathway that has not been explored in detail; previous studies involving fuel switching in the sector either view it from an energy efficiency lens or focus on a single technology. In this study, a framework is developed to evaluate and directly compare six fuel switching options (including hydrogen, biomass, municipal solid waste, and natural gas) from 2020 to 2050. Capital costs, non-energy operating costs, energy costs, and carbon costs are used to calculate marginal abatement costs and emulate cost based-market decisions. The developed framework is used to conduct a case study for Canada, using the LEAP-Canada model. This study shows that cumulative energy-related greenhouse gas emissions can be reduced by up to 21% between 2020 and 2050 with negative marginal abatement costs. Multiple fuel switching decarbonization pathways were established, reducing the likelihood that locality prevents meaningful emissions reduction and suggesting that, with low-carbon fuel and electricity policies, the sector can take significant steps towards emissions reduction. The developed framework can be applied to jurisdictions around the world for decision making, as nations move towards eliminating emissions from cement production. [ABSTRACT FROM AUTHOR]