Is emission-less propulsion possible? I believe it is...

[Think. Again.]

35. It's an interesting concept...

...I have to admit it's a new one to me.

How quickly could it be scaled?

As far as the other technologies I mentioned, yes, they will take an added expenditure of CO2 for a lmited time to pull us away from fossils, but we don't have a choice. The quicker we build out these alternatives, the more we will be displacing the use of fossils, and once we're past the apex we can continue to cut back that usage exponentially until we're safely clear of the forces behind, and sources of, CO2 emissions.

It really does come down to that. We simply must make any and every effort to stop pumping CO2 into the atmosphere if we are going to have any hope of salvaging a somewhat viable planetary ecology, and the very life that ecology supports.