Global cement producer Cemex has allied with Swiss solar start-up Synhelion to demonstrate the world’s first emissions-free cement production. Synhelion’s main agenda has been generating jet fuel from concentrated solar power, using temperatures of over 1,000 °C to ‘reverse combustion’, recombining H20 and CO2 into hydrocarbons. This is relevant to emissions-free cement production as well, as the mechanism to remove carbon dioxide from the atmosphere and instead turn it into fuel, rather than capture and storage. Powering the world’s existing cement production with renewable electricity would only reduce its emissions by a third or so, as most emissions come from limestone calcination in the process itself. Cement is 7% of the world’s total emissions, so this kind of project is…