Zero Carbon Fuel

A zero-carbon fuel emits no CO2 at the point of use, the tank-to-wake stage, the category covering ammonia and hydrogen, which contain no carbon atoms. Calling them zero-carbon is only honest at the tailpipe: their true climate value rests on the well-to-tank stage, so green ammonia and green hydrogen deliver while their grey counterparts do not. Ammonia also raises N2O and unburned-ammonia concerns, and both demand new safety regimes, so zero-carbon at use is a necessary but not sufficient test.