I really don't think we know yet (for transportation). The fuels we have are highly energetic (in particular by weight) because a lot of energy went into them to generate those tight bonds. Transportation fuels need a lot of important factors: energy density at a system level (energy per weight including storage), general safety at STP, etc.
There have been some efforts to make ptroleum products from captured CO2, which might be a temporary bridge (by definition it's GHG neutral and can use renewable power) but burning these fuels produces other pollution beyond GHGs (thus are't sustainable) so they still need to be eliminated.
Fortunately batteries appear viable for the middle of the curve, most wheeled vehicles. But at the extrema (ships, planes, and rockets), we need something that performs closer to what we have today and I don't see anything on the horizon.
I never said a single word about transportation. For urban cores, batteries are obviously quite viable today.
What I am concerned about is energy storage for power grids or microgrids.
Do you want to claim that hydrogen and ammonia can't work for this use case either, and that there is nothing viable? Implying that the most sustainable option is to just continue using fossils fuels.
What I think is that there a ways to make both hydrogen and ammonia and other options very viable not only for grid storage but also for transportation. What's holding it back is a lack of critical thinking. This is because most people's views are dictated by social circumstances and then they subconsciously find ways to rationalize them. In other words, it's hard to get people on board with solving new problems related to using different energy sources, and so executives will invent reasons it can't work.
What sort of fuel do you think makes sense to pursue for long term (months) energy storage?
> What fuels do you think are sustainable?
I really don't think we know yet (for transportation). The fuels we have are highly energetic (in particular by weight) because a lot of energy went into them to generate those tight bonds. Transportation fuels need a lot of important factors: energy density at a system level (energy per weight including storage), general safety at STP, etc.
There have been some efforts to make ptroleum products from captured CO2, which might be a temporary bridge (by definition it's GHG neutral and can use renewable power) but burning these fuels produces other pollution beyond GHGs (thus are't sustainable) so they still need to be eliminated.
Fortunately batteries appear viable for the middle of the curve, most wheeled vehicles. But at the extrema (ships, planes, and rockets), we need something that performs closer to what we have today and I don't see anything on the horizon.