Tooter, I think you will find that BP is more interested in...

Tooter, I think you will find that BP is more interested in producing hydrogen as an energy source rather than producing urea. Combining this hydrogen with nitrogen to produce ammonia is simply a method of transporting it as ammonia can be liquified with moderate pressures. The CSIRO has reported a membrane method of recovering the hydrogen with about 80% after the liquid ammonia has been transported.

If you look at the chemical compositions of ammonia and urea you will find that
ammonia is NH3
Urea is CH4N2O

So that to convert ammonia to urea you need a source of carbon C or carbon dioxide CO2 and oxygen O2 which you can get out of the air.
If you make urea starting with methane (gas) CH4 all you need to add is nitrogen and oxygen - both of which can be obtained from the air