Fair enough but too much focus on technology and not the process. Still the most environmental friendly action is to save energy, not replace it.
The largest impact to make an immidiate improvment to CO2 in road transport is to improve the process, how we manage the vehicles. To drive more energy smartly saves at least 20%, energy tires another 5-7%, correct tire pressure adds to the saving, etc etc.
Taxi´s to Arlanda may be fueled on natural gas but are still driven in a mannaer that causes, at least 20% unnecessary energy consumption.
As long as all stakeholders, focuses just on the technology, process will remain inefficient, causing unnecessary pollution.