I assume mechanized street sweepers can clear the sands and dusts off Nigerian roads and make our roads clean as European roads...Abuja has never come across to me as a city that is not green, at least on a global scale.
While I would not necessarily say it is as green as it can be, I do feel it is more green than most cities in the world.
However, it is dusty. Nigeria is NATURALLY dusty due to the trade winds from the Sahara. Abuja will require more maintenance, street cleaning etc. but let us not forget that what we experience in Nigeria does not happen in most of the world.