Designs like Eco Barge are much needed in current due to increased concentration of pollutants in the air. Yeah, it is right that the land in the urban areas is not much available for large gardens and those who own, prefer to sell it for houses or commercial purpose. This would increase the beauty of the waters where it will float.
In China, due to increased air pollution, they are constructing green buildings in which plants are integrated on every portion. They are very similar to this project. They have also developed a system to suck pollutants like CO2 from the air in the buildings and make electricity from it.
It is good to know that the world has started thinking about pollution levels which are lethal for the planet.
You did very useful hunt. Best of luck