Zero Carbon Emissions Jet Engines?

Rolls-Royce claims that its jet engines, launched after 2030, will be "capable of running with net zero carbon emissions" (https://www.theguardian.com/business/2021/jun/17/rolls-royces-jet-engines-to-run-on-synthetic-fuels-as-part-of-net-zero-plans). This contentious claim is based on a plan to replace fossil fuels with synthetic alternatives. The synthetics haven't, as yet, been approved and it's uncertain whether they will be available in the needed volumes. The synthetic fuels are described as 'sustainable aviation fuels'. This is, however, accountancy speak. Any jet engine fuel, whether synthetic or not, produces tonnes of carbon dioxide. The claim is that the massive emissions of 'greenhouse gases' by the synthetic fuels, are counter-balanced by carbon dioxide uptake by plant photosynthesis. The urgent need is to reduce the amount of carbon dioxide in the atmosphere. This needs to be done before 2030. One might wonder if aircraft could be 'forced' to continue flying with fossil fuels after 2030, if the synthetics don't become sufficiently available? It would be, apparently, relatively easy to switch the engines to using different fuels. There seems a hint of greenwash in the Rolls-Royce announcement?