A system (10) for producing carbon monoxide as a step in a process for the production of carbon neutral fuel includes heating apparatus (11) arranged to heat coal to produce coke and a limekiln (32). The limekiln (32) has an inlet (34) for the introduction of limestone, a heater (35) for heating limestone contained therein and an outlet (36) for the release of carbon dioxide. A coke chamber (39) is operatively connected to the heating apparatus (11) to receive coke therefrom and is operatively connected to the limekiln outlet (36) to receive carbon dioxide therefrom. The coke chamber (39) is configured to react received coke with received carbon dioxide, thereby to produce carbon monoxide.